Interviews and Articles

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- Interviews and Articles
Sensor module design improves automotive electrical integration,
functionality
By Torsten Herz (ZMDI)
June 2011 in EETimes
Sensor module design improves automotive electrical
integration, functionality (Part 1)
Torsten Herz, ZMDI
6/24/2011 01:58 AM EDT
Thanks to state-of-the-art sensor-based control systems that provide precise real-time monitoring,
automotive engines operate more efficiently and with lower environmental impact. One result of this
improved performance is that the number of sensor applications in vehicles has realized double-digit
growth over the past several years. The other result is a growing trend to add more sensor modules to
vehicles. Such modules must be reliable and robust and operate with long-term stability and high
precision under harsh physical, chemical, and electrical stress conditions.
Additionally, a set of built-in-diagnostic functions is required for automotive sensor modules to support
the “maintenance-on-demand” policy of automotive OEMs as well as special failure-mode-operations
required for safety-critical sensor applications like brake pressure sensing.
The chemical (i.e. media/humidity/corrosion resistance) and physical (shock; vibrations) robustness of
sensor modules is mainly determined by the materials used, and the assembly and connection
technologies. The electrical robustness (i.e. EMC) is determined by the application circuit, the chosen
electric components (ICs, discrete parts), and the layout of the electrical connections, according to the
application circuit.
This series will describe the latter aspect of the design of an automotive sensor module. The module
incorporates a sensor signal conditioner (ZSC31150) to enable the design of highly accurate sensor
modules operating at temperatures of -40 to +150C and providing EMC performance and a set of onchip-protection and diagnostic features addressing safety-critical applications at SIL2-level. By clever
electrical design of the sensor module considering all EMC-related parameters (i.e. parasitic
capacitances and inductances), high electrical robustness and built-in-diagnostic functionality can be
achieved at optimized module cost, together with very high accuracy of the measured signal.
Because the mechanical design and the interconnection between a sensor system and the processing
unit have a major influence on their electromagnetic behavior, it is essential to separate “embedded
sensing functions” and “stand-alone-sensor modules”.
In case of embedded sensing functions (ESF) the sensor electronics are placed closed to the processing
unit—in automotive applications this is an ECU (Electronic Control Unit). The connections between ESF
and ECU are typically very short (<< 30 cm) and normally realized as traces on a PCB. Modern ESF
provide a digital interface (i.e. SPI), which is connected to the microcontroller of the ECU. Because of
this closed placement on the same PCB there are several options in order to fulfill the tough automotive
requirements in terms of EMC (i.e. shielding or use of external protection parts). One example for an
ESF is barometric pressure sensing.
For stand-alone-sensor modules (SASEM), the situation is completely different. These are typically
connected to an ECU via an unshielded harness of up to 2.5 meters in length. The available board space
inside the module’s case (made of metal or plastic) is very limited and trends to further miniaturization
because lower material consumption equals lower weight, which in turn equals lower cost.
Depending on the mode of power supply (battery-powered or ECU-powered) there are various output
interfaces:
Battery-powered SASEM:
•
•
•
•
•
PWM output (high-side-load)
PWM output (low-side-load)
CAN-bus interface
LIN-bus interface
Absolute analog voltage output
ECU-powered SASEM:
•
•
•
Ratiometric analog voltage output
SENT interface (fast digital unidirectional point-to-point data transfer)
PSI5 interface (digital 2-wire-current-coded data transfer)
Typical construction of an automotive pressure sensor module
For passenger cars it is still very common to use ECU-powered SASEMs, which provide a ratiometric
analog voltage output. The typical supply voltage amounts to 5 VDC ±10% and the current consumption
of a SASEM should amount to ≤10 mA. The operational conditions are quite harsh as mentioned at the
beginning, which leads to the exclusion of some effective passive protection parts such as ferrite beads,
which operate at temperatures only up to +125C.
Depending on the module’s design (i.e. the material of the module’s case), two additional 10nF
(maximum) capacitors (shown in green in the figure below) at the differential inputs VINP and VINN to
VSSA might be required in order to fulfill the EMC specification of the SASEM—this leads us to typical
automotive EMC requirements.
ZSC31150 automotive application circuit
Basically the electromagnetic characteristic of systems like SASEMs is split into areas—electromagnetic
emissions (conducted or radiated) and electromagnetic immunity (conducted or radiated). The limitation
of electromagnetic emissions ensures that other electrical systems are not disturbed by operation of a
SASEM. Thus, the active electronics inside a SASEM determine its “emission performance.” By proper
IC design and at digital on-chip-clock frequencies <5 MHz (i.e. ZSC31150 for DSP-on-chip typically
operates at 3 MHz), common ISO- and OEM-standards for electromagnetic emissions of SASEMs can
be fulfilled.
Electromagnetic immunity
In terms of electromagnetic immunity against continuous or transient RF energy, there are several
standardized test methods for both conducted and radiated modes of RF-energy transfer to the SASEM.
Because of the small dimensions of the SASEM itself and of its internal conductive parts, there is no
effective RF antenna for radiating RF energy up to 1 GHz—all dimensions are smaller than the length la
of an equivalent λ/4 dipole. On average, this length is approximately 50 mm at 1 GHz as calculated with
equation (1).
Up to 1 GHz, the primary effective antenna for RF energy is the SASEM’s harness. However, there is a
trend to expand the EMC test procedure frequency range to 3 GHz (or more). In this case, the effective
length la of an equivalent λ/4 dipol decreases to approximately 20mm as calculated by equation (1), and
conductive structures on the module’s PCB with a length >15mm can be an effective antenna for
radiated RF energy. To prevent susceptibility at field strengths up to 600V/m, shielding of sensitive signal
paths might be required.
Their susceptibility is measured by EMC test procedures. There are different test configurations for
radiated and conducted immunity (i.e. stripline, anechoic chamber, bulk current injection, etc). One of the
toughest tests for common automotive SASEMs regarding immunity against continuously applied RF
energy is the Bulk Current Injection (BCI) test, which belongs to the radiated immunity EMC test group.
Typically the frequency range tested is 1 to 400 MHz. The test simulates worst case conditions for RF
cross-coupling in a harness for different electric subsystem’s wires assembled inside a car. Because of
the small distance between RF source (emitting harness or wire) and RF sink (harness of the sensor
module), the induced energy can be very high and is measured in “mA” or “dBµA” during the BCI test. To
ensure the induced energy can influence only the sensor module during the test, the ECU is replaced by
a standardized artificial network and typical circuitry at VSIGNAL, which represents the input impedance
of the original ECU used in the car as shown below.
BCI test circuitry and equivalent RF circuitry of the SAREM for the circuit in the first figure on the previous page and Case 1 in the
table to follow
It is important to note, customizing this circuitry for each EMC test before designing the module is
strongly recommended because different EMC test circuitries can make different module designs
necessary. Typically “universal” solutions are too expensive.
To fulfill the harsh automotive EMC requirements, all relevant electrical parasitics, especially
capacitances between the electric sensor circuitry and other conductive parts of the SASEM, need to be
considered as shown in the figure above.
There are a number of different configurations possible for the module’s construction and its assembly
inside the car as listed in Table 1 below. The case and the pressure supply adaptor (PSA) can each be
plastic or metal and each can have a galvanic contact with the chassis or no contact.
Table 1: Possible configurations of module construction and automotive assembly
In Table 1, configurations 1 and 10 represent the extremes regarding the equivalent RF circuitry at the
BCI test. With configuration 1, all parasitic impedances are maximums; with configuration 10, they are
minimal or short circuited.
The first consideration is the electromagnetic coupling between the BCI antenna and the harness. If the
frequency of the RF current IRF is in the range of the initial resonance frequency of the segment of
harness between the RF-emitting BCI antenna and the DUT, then the induced current IRF_sink is
maximum. The induced current value is determined by the parasitic impedances, especially by ZC_GND.
As IRF_sink increases, its influence on the DUT becomes stronger. The worst case is configuration 10,
because ZC_GND = 0 Ω (galvanic contact between case and the car’s chassis) and ZPSA_C = 0 Ω
(galvanic contact between PSA and case). In this case IRF_sink is limited by the impedance of the
parasitic capacitances of the DUT’s signal paths V+, VOUT, and V- relative to the case and of the sensor
bridge relative to the PSA.
But there are additional parasitic capacitances (i.e. the internal signal paths relative to the case), which
could also decrease the RF susceptibility of the DUT.
An example:
•
•
•
Tolerance allowed for the analog output voltage of the DUT = ± 40 mV (nominal value)
Effective gain “G” of the SSC-IC: G = 400
DC bridge resistance = 4 kΩ / resulting AC bridge impedance at its differential terminals = 2 kΩ
Thus the limit of the differential bridge voltage’ s change caused by RF energy: (± 40 mV / G) = ± 0.1
mV. And the resulting limit of the difference between the bridge’s partial currents: ± 0.1mV/2kΩ = ±
50nA!
This very simplified example illustrates the influence of the mechanical construction and selected
materials on the EMC behavior of the sensor module. It is even more challenging to define parasitics
under the conditions of high volume automotive production with consideration for the system’s cost.
Torsten Herz, is FAE manager at ZMDI.
Smart sensor for high-resolution high-precision noise ratio measuring
performance digital signal correction
By Marko Mailand (ZMDI)
February, 2012 in Semiconductor Network
Application Review
고해상도 저잡음 정밀 스마트 센서 위한
비율계량성과 디지털 신호 보정
특수한 아날로그 및 디지털 센서 신호 처리 개념을 사용하여 간섭에 대해 내성이 있는 고정밀도 센서 신호 측정을 지원할 수 있다.
비율계량성(ratiometricity) 또는 신호 조정 등과 같은 제시된 개념들을 적절히 활용함으로써 에너지 효율적인 고성능 표준 솔루션을
신속하게 개발할 수 있다.
글/마르코 마일랜드(Marko Mailand) 의료, 소비가전, 산업 사업부, ZMDI
센
서 및 센서 시스템에 대한 오늘날의 고객들은 모듈
크기, 동작 복잡성, 가격, 에너지 소모 등은 물론
전체 비용의 절감과 같은 성능 파라미터가 향상되기를 기
대하고 있다. 압력, 온도, 무게, 유량, 토크, 진동, 장력,
변형 등과 같은 환경 조건들을 결정할 때 정보와 및 성능
성능을 제공하고 있다. 예를 들어, 궁극적으로 최종 측정
요구사항에 대한 일반적으로 끊임없이 증가하고 있는 요
결과가 전체 신호 범위의 수십 %에 이르는 잡음을 나타낼
구로 인해 소비가전과 산업용 애플리케이션 모두에 대한
지라도 기업들은 일반적으로 16bit 신호 해상도를 제공하
요구 역시 지속적으로 증가하고 있다. 이것은 결과적으로
는 인터페이스 또는 신호 조정 IC를 광고하여 제공하고 있
센서 민감도, 해상도, 간섭 내성, 정밀도 등에 대한 보다
다. 이러한 경우에 사용자들은 요구되는 성능을 가상 형태
높은 요구로 이어진다. 이러한 맥락에서 직접 버스 연결
로만 확인할 수 있는 데, 최종 측정 결과의 낮은 신호 품질
을 제공하는‘스마트 센서’시스템 개념은 최근 수년 동
로 인해 예를 들면 원래의 범위에서 사실상 10bit에서
안 지속적으로 폭넓게 수용되어 왔다. 이러한 시스템 접
12bit 정도에 불과한 유효 해상도만이 제공되기 때문이다.
근법은 일반적으로 다음과 같은 기능 요소들로 구성되어
이러한 이유로 인해 시스템 개념들뿐만 아니라 회로별 아
있다: 센서, 아날로그 신호 조정(증폭, 오프셋 보정 등),
날로그 간섭의 제거, 보상, 또는 적어도 최소화가 여전히
아날로그-대-디지털 변환, 디지털 신호 보정, 버스 인터
필요하고, 다시 말해 보다 소형화된 기술로 이동하는 경우
페이스, 디지털 분석.
에 반복적으로 중요한 태스크가 되고 있다.
현재 스마트 센서는 특히 고정밀도 센서 애플리케이션
다행스러운 것은 기반 기술에 상관 없이 고해상도의
과 함께 사용될 경우에 시장에서 출시되고 있는 새로운 제
에너지 효율적인 저잡음 스마트 센서를 구현할 수 있는
품들을 위한 사실상의 표준으로 간주되고 있지만, 여전히
유효하고 매우 효과적인 회로 토폴로지와 접근법이 존재
실제 신호 조정 및 처리와 관련하여 매우 다양한 수준의
한다는 것이다.
90 Semiconductor Network 2012.2
고해상도 저잡음 정밀 스마트 센서 위한 비율계량성과 디지털 신호 보정
비율계량성(ratiometricity)
전압 VDD의 IC-내부 절대 수준이 변화하는 경우에도
A2D-컨버터의 출력 Zout에 대한 스퓨리어스 영향은 나타
비율계량 측정 원리는 전력공급에서 간섭 현상을 제
거하는 데 일반적으로 사용되는 개념이다. 비율계량 측정
나지 않는다. 원칙적으로 다음 식을 이 경우에 적용할 수
있다:
방법에서 요구되는 측정 양은 일반적으로 간섭을 나타내
는 2개의 양의 비율이다. 하지만, 이와 관련해서 간섭이
(
Zout =2resolution· GAMP·
실제 측정에 영향을 미치지 않는다는 것이 중요하다. 예
를 들어, 비율계량 값은 공급전압에 대해 독립적이다.
)
Voff
VIN
+
Vrp -Vrn ,
Vrp -Vrn
여기서 GAMP은 증폭을, Voff은 신호 경로 내의 내부 오프
그림 1은 측정된 전압 V1과 V2에 대한 저항 R1과 R2의
셋을 나타낸다. 뿐만 아니라, 향후 SSC 세대를 위해 개념
비율이 공급전압의 절대값 VDD에 대해 독립적이라는 것
들의 적용 가능성이 최적의 전압 레귤레이터를 사용하여
을 보여주고 있다. 결과적
저전력 공급전압을 한층 더 억제하기 위한 학계와 산업의
으로 R1의 값을 알고 있을
그림 1. 비율계량 측정 회로
의 기본 예제
연구 과제이다. 따라서 LDO(low dropout regulator)를
경우에 전압의 비율을 측
통해 스마트폰과 같이 상당한 수준의 간섭이 나타나는 환
정한 다음 공식: R2 = R1·
경들에서 고해상도 저전력 센서 시스템을 사용할 수 있
V2/V1을 사용하여 저항 R2
다. 이와 관련하여 전압 레귤레이터는 신호 경로의 기성
를 결정할 수 있다.
커패시턴스로 인한 동적 손실을 감소시켜 16bit에서
시스템-통합 접근법의
24bit까지의 유효 해상도와 각 실리콘-공정과 관련된 최
경우, 이 원리를 확장하여
소 트랜지스터 공급 전압까지 동작 전압을 제공하면서 동
복잡한 센서 인터페이스와
시에 비율계량 신호 경로를 활용하는 시스템을 제공할 수
SSC(sensor signal conditioning) IC(예를 들어, ZMDI
있다.
의 ZSI21013와 ZSSC30xx, MAXIM의 MAX1452,
ATMEL의 AT77C104Bx 등이 있다)에서 사용할 수 있다.
신호 조정 및 AZ(auto-zero) 조정
비율계량 토폴로지를 통해 공급전압 간섭에 대해 근본적
으로 내성을 가지고 있으면서 16bit의 유효 신호 해상도를
아날로그 성능 파라미터들 외에도 디지털 신호를 보
제공하는 거의 잡음이 없는 애플리케이션을 지원할 수 있
정할 수 있는 표준 SSC의 성능 역시 매우 중요하다. 일반
다. 기본적인 비율계량 원리를 SSC의 증폭기와 ADC
적으로 센서 시스템들은 센서 요소 자체의 특성은 물론
(analog-digital converter)
에 적용할 수 있다. 이 경우,
그림 2. 저항 브리지 센서 신호 측정을 위한 비율계량 토폴로지
내부 IC 레퍼런스 전압 Vref
또는 Vrp 및 Vrn를 저항 브리
지 센서 요소의 공급전압 VDD
로부터 직접 얻을 수 있다(그
림 2). 결과적으로 VDD에 대
한 간섭이 시스템적으로
ADC의 입력 전압에 대한 센
서 전압 VIN의 비율에 영향을
미치지 않는다. 따라서, 공급
2012.2 Semiconductor Network 91
Application Review
실제 가변 측정 값(기압, 수압, 비틀림 진동 등)으로 인해
Wire Interface), I2C, SPI 등과 같은 유연한 디지털 인
고유한 비선형성을 나타낸다. 뿐만 아니라, 센서 신호와
터페이스를 제공한다. 일반적으로 프로그램 가능한 해상
환경 또는 센서 시스템 온도 사이에는 비선형적인 관련성
도와 분할을 제공하는 CB(charge-balancing) 아키텍처
이 나타난다(저항 센서에 대해서는 적용되지 않는다).
가 보다 낮은 샘플링 속도를 제공하는 저전력 애플리케이
결과적인 측정 값을 선형화시켜 최적의 방법으로 연
션의 ADC를 위한 기본 IP로서 사용되며, 시그마-델타
속적인 분석을 지원하기 위해서 최신 SSC들은 수많은 신
접근법들은 1k sps(sample per second) 이상의 샘플링
호 조정 계수들을 사용하는 디지털 처리 유닛을 특별히
속도를 제공하면서 상대적으로 전력이 중요하지 않은 스
채택하고 있다. 해당 요구 보정 지점들은 각 센서 IC에
마트 센서 시스템에 채택된다.
따라 달라지며, 개별적으로 획득되어야 하기 때문에 센서
분할된 CB-ADC의 경우, 완전 MSB(most significant
시스템의 어셈블리 시에 일반적으로 수행된다. 뿐만 아니
bit) 변환과 통합 MSB/LSB(least significant bit) 변환
라, 이러한 강화된 SSC는 통합 온도 센서를 제공하여 통
사이에서 선택할 수 있다. 두 경우 모두, 특정 영역의 애
합 브리지 센서와 온도 신호 보정의 모든 이점들을 유지
플리케이션을 위한 최종 측정 값에서 변환 속도와 추가적
하면서 BOM(bill of material)을 최소화시킨다.
인 잡음 감소에 대한 알맞은 비율을 선택하여 지정할 수
‘AZ(auto-zero) 측정’
을 사용하여 내부 회로 신호 오프
있다. 아날로그 전치-증폭(정밀하게 프로그래밍될 수 있
셋 Voff을 계산할 수 있기 때문에 최종적으로 센서 신호를
음) 및 조정 가능한 ADC 입력 오프셋 시프팅을 사용하여
실제 요구되
이와 같은 IC들을 환경적인 신호와 센서 요소 특성들(특
는 값으로 보
히 오프셋, 민감도, 측정 범위 등)에 따라 결정되는 다양
정할 수 있다.
한 신속 곡선들에 대해 최적화시킬 수 있다. 무엇보다 표
이렇게 하기
준이지만 애플리케이션 지정 IC로서의 이용 가능성 때문
위해서 신호
에 특정 시장에서 임지 경쟁이 시작되었다: 각 SSC 회로
경로를 IC 입
들에 대한 지속적인 기술 향상(기능 및 파라미터), 소형
력에서 직접
화, 저비용화. 결과적으로 이러한 기본적이고 고유한 사
단락시킨다
실은 새로운 미래형 스마트 센서와 개별 애플리케이션들
(그림 3). 신
의 개발을 위해 공통적으로 이용 가능한 다양한 센서 신
호 보정뿐만
호 조정 IC를 제공한다.
그림 3. 센서 시스템의 보정. 고장 영향 보상 및 선형화
아 니 라 AZ
측정 역시 시스템 안정성, 드리프트 동작 등과 같은 파라
에너지 효율은 필수사항
미터들을 모니터링하기 위한 고유한 애플리케이션 진단
기능들을 지원한다.
최대 1mA의 전류 소모 특성(A2D 컨버터 등)으로 최
이러한 방법들 덕분에 비선형 및 온도 민감 변수들과
소 1.8V의 낮은 공급전압 조건에서 동작하는 것은 기존
센서 신호 모두를 연결된 실제 정보 처리 단을 위해 이상
및 향후 SSC를 위한 오늘날의 표준 요구사항이자 최신
적으로 준비할 수 있다(그림 3).
기술이다. 가능한 그 이상으로 에너지 효율적인 센서 애
플리케이션을 만들기 위한 하나의 접근법은 SSC가 다양
표준 기능
한 동작 모드를 제공하도록 하는 것이다. 이와 관련하여
일반적으로 사용되는 3가지 주요 모드는 다음과 같다(그
앞서 언급한 특성들, 현재 및 미래의 센서 인터페이
스, SSC 회로 등은 업계-표준을 준수하며, OWI(One-
92 Semiconductor Network 2012.2
림 4와 비교).
•연속/업데이트 모드: 모든 IC-내부 블록들에 지속
고해상도 저잡음 정밀 스마트 센서 위한 비율계량성과 디지털 신호 보정
적으로 전력이 공급된다. 측정 요구에 대한 IC
그림 4. 일반적인 SSC 동작 모드
반응이 최대이다. 심지어 A2D-변환이 수행되
지 않는‘비활성’기간에도 전류가 소모된다.
이와 관련하여 추가적인 측정 요구 명령어 없이
주기적인 업데이트 측정이 수행된다. 그에 맞게
각 결과들을 조사할 수 있다.
•슬립/웨이크-업 모드: 거의 인터페이스만이 디
지털 인터페이스 버스에 집중하고 있다. 유효한
명령어를 수신한 경우에만 개별적으로 필요한
IC-블록들에 전력이 공급되고, 명령어 요청, 예
를 들어 센서 측정 수행 등이 처리된다. 따라서,
IC-활성화가 필요하지 않을 경우에는 대기 전
류만이 소비된다. 반면, 명령어 요청에 대한 응
답 시간이 연속 또는 업데이트 모드 대비 다소
늦어진다.
•명령어/테스트 모드: 모든 IC-내부 블록들에
전력이 공급되지만 명령어에 의해 오프 상태로
전환될 수 있다. IC 시스템 아키텍처에 대한 특수한
계산 유닛 등보다 넓은
지식과 정보가 필요하다. 일반적으로 이러한 종류
공급전압 범위에 대해
의 동작 모드는 테스트 목적을 위해 사용되거나 개
설계된다. 후자들이 최
별 고객의 SSI 및 SSC 디바이스에 대한 IC-제조업
소(내부 레귤레이션) 공
체의 애플리케이션별 지원을 가능하게 한다.
급전압 조건에서 동작
그림 5. 헤더
한다. 일반적으로 SSC
예를 들어, ZMDI의 ZSSC3016의 경우, 특히 슬립 모
-디바이스가 외부 연
드가 평균 전력소모를 최소화시킨다. 슬립 모드에서 회로
결 센서 요소들에 대한
는 사실상 파워-다운 상태(1μ
A 미만의 전류 소모 가능)이
공급전압(최소 내부 레
기 때문에 버스 명령어 또는 적절한 회로 ID를 수신한 경
귤레이션 공급전압임)
우에 1초 이내에 웨이크-업 상태가 될 수 있다. 웨이크-
도 제공한다. 결과적으
업 상태가 되면 IC가 즉시 대기 모드로 복귀한 다음 완벽
로 센서 요소의 전류 소모 특성 역시 SSC의 낮은 다운-레
한 센서 측정이 수행된다. 인터페이스 프로토콜에 따라서
귤레이션 공급전압에 의해 낮아진다. 결과적으로 초당 1
결과적인 측정 값을 대기(저전력) 모드에서도 평가할 수
회의 벤치 테스트 시나리오에서 이용 가능한 첨단 회로들
있다. 유사한 전력 감소 성능이 MAXIM, ATMEL 등의
이 100μ
A 이하의 평균 전류 소모 특성을 제공한다.
IC들에서 제공되고 있는 것으로 알려져 있다.
마지막으로 최신 SSC-회로 제품의 출시로 인해 최근
전체 전력 소모 특성에 영향을 주어 최소화시킬 수 있
까지 ASIC-기반 또는 개별 칩 솔루션을 통해서만 제공
는 추가적인 접근법은 전압 영역 분할(voltage domain
되었던 성능 파라미터들과 지원하면서도 크기가 최적화
sectioning)이다. 따라서, 레귤레이터, 리셋 블록, IC의
되고 에너지 효율적인 스마트 센서를 개발할 수 있는 표
인터페이스 등이 아날로그 센서 프론트-엔드 및 디지털
준 IC 시장이 제공되게 되었다.
SN
2012.2 Semiconductor Network 93
03/2012
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Analog-/Mixed-Signal-ICs
Energieeffizienz und störfeste
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DIGIKEY.COM
01_U1-Titelseite.indd 3
06.03.2012 15:43:57
012712_FRSH_EIND_DE_snipe.indd 1
1/27/12 12:08 PM
Analoge-/Mixed-Signal-ICs
Nutzsignalauflösung: 16 effektive Bit
Energieeffizienz und störfeste Sensor-Signalverarbeitung
Die Erweiterung bekannter, analoger und digitaler Sensorsignalverarbeitungskonzepte mit gezielten Energiesparlösungen ermöglicht störfeste, hochgenaue Sensorsignalmessungen bei reduzierter Leistungsaufnahme. Die
Umsetzung der hier adressierten Konzepte ebnet den Weg für energieeffiziente High-Performance-StandardLösungen im Bereich der Smarten/Intelligenten Sensoren.
Autor: Dr. Marko Mailand
H
eutige Marktanforderungen an Sensoren und Sensorsysteme erwarten steigende Leistungsparameter bei sinkenden Gesamtkosten: Modulgröße, Bedienkomplexität,
Preis und Energieverbrauch. Die Ermittlung von Umgebungseigenschaften, wie beispielsweise Druck, Temperatur, Gewicht, Durchfluss, Drehmoment, Vibration, Tension, Dehnung,
etc. führen dabei sowohl im Consumer-Bereich als auch im Industriesektor zu stetig wachsenden Ansprüchen an die Empfindlichkeit bzw. Auflösung, Störfreiheit und Genauigkeit. In diesem Zusammenhang hat sich das Systemkonzept des intelligenten Sensors
(smart sensor) mit direkter Busanbindung in den letzten Jahren
immer mehr etabliert. Intelligente Sensoren setzen sich dabei prinzipiell aus den Funktionselementen: Sensor, analoge Signalaufbereitung (zum Beispiel Verstärkung, Offsetkorrektur) Analog-Digital-Wandlung, digitale Signalkorrektur und digitale Auswertung
zusammen.
Während insbesondere für hochgenaue Sensorapplikationen der
smarte bzw. intelligente Sensor de facto als Standardkonzept für
Neuerscheinungen am Markt gilt, existiert noch immer eine sehr
68
68_ZMDI 595 jj.indd 68
unterschiedliche Leistungsbandbreite, was die eigentliche Signalaufbereitung und -verarbeitung und insbesondere die Leistungsaufnahme angeht. So ist es beim Übergang zu kleineren Technologien immer noch und immer wieder eine Hauptaufgabe, alle schaltungsspezifischen, analogen Störeinflüsse zu eliminieren, zu kompensieren oder zumindest zu minimieren. Anderseits sind
bewährte Konzepte und Lösungen zu verändern, um den Forderungen nach Energieeffizienz nachzukommen. Häufig führt dies
zu konträren Lösungskonzepten.
Nichtsdestotrotz existieren Schaltungstopologien und -ansätze
die technologieunabhängig ihre Gültigkeit und insbesondere ihre
Wirksamkeit für die Realisierung von hochauflösenden, energieeffizienten, rauscharmen, intelligenten Sensoren behalten.
Einfacher Ansatz – Große Wirkung
Ein vielfach eingesetztes Konzept zur Beseitigung von Störeinflüssen auf der Spannungsversorgung ist das ratiometrische Messprinzip. Ratiometrische Messungen zeichnen sich dadurch aus, dass
das Messergebnis als Quotient zweier Größen gesucht ist, welches
02.03.2012 15:51:08
typischerweise von Störungen überlagert
ist. Dabei ist jedoch ausschlaggebend, dass
die Störungsüberlagerung die eigentliche
Messung nicht beeinflusst. Eine ratiometrische Größe ist zum Beispiel unabhängig
von der Versorgungsspannung.
Bild 1 zeigt am einfachen Beispiel, dass
das Verhältnis der gemessenen Spannungen V1 und V2 an den Widerständen R1
und R2 unabhängig vom Absolutwert der
Betriebsspannung VDD ist. Somit kann bei
bekanntem Wert für R1 durch Messung des
Spannungsverhältnisses auf das Widerstandsverhältnis bzw. auf R2 geschlossen
werden, wobei gilt: R2 = R1 x V2 / V1.
Genau dieses Grundprinzip wird in Sensorinterface- und Sensor-Signal-Conditioning Standardschaltkreisen (SSC) von ZMDI (beispielsweise ZSSC3016 und
ZSSC3017) eingesetzt, um quasi rauschfreie und betriebsspannungs-störfeste Applikationen mit einer Nutzsignalauflösung
von effektiven 16 Bit zu ermöglichen. Als
Erweiterung des ratiometrischen Grundprinzips werden hierbei die IC-internen
Referenzspannungen beispielsweise für
den Verstärker und den Analog-DigitalWandler (ADC) direkt von der entsprechenden Versorgungsspannung VDDB des
resistiven Brücken-Sensorelements abgeleitet (Bild 2). In Folge dessen wirken sich
Störungen auf VDDB nicht auf das Verhältnis der Sensorspannung VIN zur Eingangsspannung am AD-Wandler aus. Dies führt
wiederum dazu, dass bei verbleibenden
Schwankungen auf der Versorgungsspannung VDDB zwar die IC-internen Absolutpegel variieren, jedoch keinerlei Schwankungen im Wandlungsergebnis auftreten.
Für die neueste SSC-Generation von
ZMDI wurde dieses Konzept erweitert.
Mittels leistungsarmer Betriebspannungsunterdrückung durch einen geeigneten
Spannungsregler ist es mit dem ZSSC3016
möglich, low-power Sensorsysteme in stark
gestörten Applikationsumgebungen einsetzen zu können, zum Beispiel in SmartPhones. Der Spannungsregler verringert
dabei dynamische Verluste an parasitären
Kapazitäten im Signalpfad und ermöglicht
einerseits 16-Bit-genaue Systeme bei Betriebsspannungen bis 1,8 V unter gleichzeitiger Ausnutzung eines ratiometrischen
Signalpfades.
Energieeffizienz durch clevere
Spannungsversorgung
Der Betrieb bei niedrigen Betriebsspannungen bis hinunter zu 1,8 V bei gleichzeitiger IC-Stromaufnahme von höchstens 1
mA sind Grundansätze, die bei aktuellen
SSC-Neuentwicklungen von ZMDI, wie
dem ZSSC3016, verfolgt werden. Um darüber hinaus energieeffiziente Sensorapplikationen zu ermöglichen, bieten ZMDI-SSCs
verschiedene Operationsmodi, wobei insbesondere der Wake-Up- oder Sleep-Mode
den Gesamtenergieverbrauch minimiert.
Dabei ist der Schaltkreis in einem QuasiPower-Down-Zustand (Stromaufnahme
weniger als 250 nA), aus dem er innerhalb
weniger Sekundenbruchteile per BusKommando oder passende Schaltkreis-ID
aufgeweckt werden kann, worauf eine
komplette Sensormessung durchgeführt
wird und der IC unmittelbar wieder in den
Ruhezustand zurückkehrt. Je nach Interface-Protokoll kann das Messergebnis auch
im Ruhezustand abgerufen werden.
Mit dem in Bild 2 realisierten Systemkonzept wird unter Nutzung so genannter
Low-Dropout-Regler (LDO) eine weitgehend stabile, sehr niedrige Betriebsspannung (VDDB = 1,7 V) erzeugt. Der gesamte
analog-digitale Sensormesspfad wird auf
dieser niedrigen Spannung betrieben. Da,
nicht zuletzt aufgrund des ratiometrischen
Ansatzes, auch das eigentlich Brückensensorelement von VDDB gespeist wird, kann so
die Gesamtstromaufnahme des Intelligenten Sensors minimiert werden.
Zusätzlich wurde zum Beispiel im
ZSSC3016 der LDO so ausgelegt, dass er
eine stabil-geringe Versorgungsspannung,
VDDB auch unter extremen Bedingungen
erzeugen kann, wie sie in mobilen Endge-
Auf einen Blick
Ratiometrisches Messprinzip
Die Trennung der Betriebsspannungs-Domainen für Interface- und Signalverarbeitung ermöglicht einen neuen Grad an Energieeffizienz für hochgenaue intelligente Sensoren. Zur Beseitigung von Störeinflüssen auf der Spannungsversorgung wird das ratiometrische Messprinzip in
Sensorinterface- und Sensor-Signal-Conditioning-ICs von ZMDI (beispielsweise ZSSC3016 und
ZSSC3017) eingesetzt, um quasi rauschfreie und betriebsspannungsstörfeste Applikationen mit
einer Nutzsignalauflösung von effektiven 16 Bit zu ermöglichen.
infoDIREKT www.all-electronics.de
595ei0312
02.03.2012 15:51:12
Analoge-/Mixed-Signal-ICs
räten zu finden sind; eine Betriebsspannungs-Störunterdrückung
von bis 90 dB ohne die Notwendigkeit zusätzlicher, externer Komponenten steht hier zur Verfügung.
Analoge Korrektur ist nur die Hälfte
Analoge Leistungsparameter sind für die letztliche Sensormesswertqualität sehr wichtig; doch die digitale Signalkorrekturfähigkeit ist ebenfalls von wesentlicher Bedeutung. Typischerweise besitzen Sensorsysteme eine inhärente Nichtlinearität, welche sich
sowohl aus der eigentlichen Messgröße ergibt (zum Beispiel Höhenluftdruck, hydrodynamischer Druck und Torsionsschwingung)
als auch aus der Sensor-Charakteristik selbst. Zusätzlich besteht
nicht nur bei resistiven Sensoren häufig ein nichtlinearer Zusammenhang zwischen Sensorsignal und Umgebungs- bzw. Sensorsystemtemperatur. Um daraus resultierende Messwertverläufe zu linearisieren und dadurch für die nachfolgende Auswertung optimal
nutzbar zu machen, beinhaltet der ZSSC3016 beispielsweise eine
speziell angepasste, digitale Verarbeitungseinheit, welche bis zu 7
verschiedene 18 Bit genaue Kalibrierkoeffizienten berücksichtigen
kann. Die entsprechend notwendigen Kalibrierpunkte sind für jedes Sensor-IC-Paar spezifisch und müssen jeweils separat, in der
Regel während der Inbetriebnahme des Sensorsystems, ermittelt
werden. Dazu unterstützten die ZMDI-SSCs derartige Korrekturmethoden durch zusätzlich integrierte Temperatursensoren, die
Bild 3: Typische Operationsmodi von ZMDI: Sensorinterface- und SensorSignal-Conditioning-ICs.
70
Alle Bilder: ZMDI
Bild 1, oben: Basisschaltung ratiometrisches Messen.
Bild 2, rechts: Trennung von Interface
und Ratiometrischer Topologie für
energieeffiziente, resistive Brückensensor-Signalmessung (zum Beispiel im
ZSSC3016 von ZMDI).
wie im ZSSC3016 mit einer rauschfreien Auflösung von unter
0,005 K/LSB im Bereich -40...+85 °C eine eigene Klasse für sich
bilden könnten.
Darüber hinaus können schaltkreisinterne Signaloffsets, Voff
über eine so genannte Auto-Zero-Messung (AZ) bestimmt und
letztlich das eigentlich gewünschte Sensorsignal damit korrigiert
werden. Dafür wird direkt am IC-Eingang der Signalpfad kurzgeschlossen. Zusätzlich zur Signalkorrektur ermöglicht die AZ-Messung die inhärente Applikations-Diagnose zur Überwachung von
zum Beispiel Systemstabilität und Driftverhalten.
Mit diesen Methodiken lassen sich nichtlineare und temperaturabhängige Messgrößen und Sensorsignale optimal für die eigentliche, auf die Messwertermittlung folgende Informationsverarbeitung vorbereiten.
Standard-Features
Bestehende und zukünftige Sensorinterface- und SSC-Schaltkreise
von ZMDI bieten neben den erläuterten Eigenschaften unter anderem industriestandard-konforme und inhaltsflexible Digitalschnittstellen, wie I2C (bis 3,4 MHz) oder SPI (bis 20 MHz). Als
Basis-IP für den ADC wird eine in Auflösung und Segmentierung
programmierbare Charge-Balancing-Architektur eingesetzt. Hier
kann zwischen reiner MSB-Wandlung (Most Significant Bit) und
kombinierter MSB/LSB-Wandlung (LSB, Least Significant Bit) gewählt werden, wobei ein anwendungsspezifisches Optimum zwischen Wandlungsgeschwindigkeit und weiterer Rauschreduktion
des Messergebnisses einstellbar ist. Komplett SSC-korrigierte,
16-Bit-aufgelöste Wandlungsergebnisse können mit einer Rate von
bis zu 175 s-1 erzeugt werden. Mittels feinstufig programmierbarer,
analoger Vorverstärkung und anpassbarer ADC-EingangsoffsetVerschiebung lassen sich ICs, der ZSSC31016 und andere auf verschiedenste Signalverläufe von Umgebungssignal sowie Sensorelementcharakteristiken (insbesonders Offset, Empfindlichkeit und
Messbereich) und somit für nahezu jede Messaufgabe anpassen.
Letztlich bietet ZMDI dem Markt für Standard-ICs mit seinen
16-Bit-Schaltkreisen die Möglichkeit, größenoptimierte und energieeffiziente, intelligente Sensoren mit Leistungsparametern zu realisieren, die bisher nur von ASIC-basierten oder Einzelchiplösungen bekannt waren. (jj)
n
Der Autor: Dr. Marko Mailand ist Projektmanager für MixedSignal-IC-Entwicklung im Bereich Medical, Consumer und
Industrial bei ZMDI in Dresden.
02.03.2012 15:51:15
IO-Link – Universal, Smart and Easy
ByDaniel Heinig (ZMDI)
August, 2012 in ENGINEERLIVE
IO-Link – Universal, Smart and Easy
The IO-Link interface provides an “intelligent” method for closing the “last meter” in the IO (inputoutput) field level of factory automation and reduces costs as well as staff-hours for engineering,
installation and maintenance.
In process and factory automation, tremendous progress has been made in the last decades, as can
be seen when comparing today’s sensors and actuators with those from the early days of
automation. The original idea was to use electromagnetic, hydraulic or pneumatic devices to
automate repetitive processes. Then came freely programmable logic controllers (PLCs), more
electronic advances and the evolution of intelligent interfaces, resulting in development of a huge
number of highly integrated and powerful sensors and actuators. Today, simple binary switches have
evolved into intelligent communicative sensors.
In this context, “intelligent” describes sensor or actuator devices that have, on the one hand, the
ability to recognize and report defined conditions, and on the other hand, the capability to be
diagnosed during error conditions and configured in the field. However, these bidirectionally
communicating devices need simple interfaces to communicate with the PLCs. Moreover,
communication for calibrating the sensor/actuator devices is needed in most cases. In the past, many
device manufacturers developed their own propriety communication solutions for calibration.
This “last meter” gap in factory automation can be closed with a smart interface based on the IO-Link
specification, which is defined by the IO-Link Consortium. IO-Link provides a simple and easy-to-use
interface for intelligent sensor or actuator devices, as well as for more simple analog and digital
sensors and actuators. They are connected via a master on a field bus to a PLC or a parameter server.
Here the IO-Link serves not as a bus system, but as a point-to-point connection with the objective of
ensuring downward compatibility and integration into all bus systems in factory and process
automation. That means standardized M12, M8 and M5 connectors with three-wire cables up to 20
meters in length can be used. IO-Link uses the IEC 61131-2 standardized 24V DC signal.
IO-Link is an international standard, which means it is likely to supersede most proprietary solutions
in the future. In addition to the benefits in the actual application area within a fabric, a positive
impact is that there will be a uniform “sensor language” at locally dispersed manufacturing locations.
IO-Link communication between master and device uses a signal that can be processed with a
standard UART (today’s standard for many microcontrollers). Because IO-Link is a point-to-point
connection, communication via the IO-Link telegram is much easier compared to bus
communication. Communication conflicts and the long cycle times needed to recover from conflicts
do not occur with IO-Link.
IO-Link offers three communication rates: COM1, COM2 and COM3. The COM1 data rate is 4.8
kBaud. COM 2 has a data rate of 38.4 kBaud, which is the most common speed, and the COM3 rate is
230.4 kBaud.
Benefits with IO-Link
With IO-Link, a world standard is already in place. It is system and field-bus independent and can be
integrated into all types of sensors and actuators.
The installation of IO-Link devices is cost-neutral. Traditional (three-wire) cables, including typical
connection methods, can be used.
Using IO-Link, devices can be parameterized during operation. Central data from a parameter storage
server enable immediate parameterization. Complex local programming can be a thing of the past,
which is especially advantageous for very small devices with difficult access. With IO-Link, the down
times for programming are significantly reduced (up to 90%) and the quality of the production
equipment is much higher.
IO-Link also offers a wide range of diagnostics for the sensor or actuator device itself. For example,
pollution, abrasion, temperature, pressure and voltage levels can be monitored and remote
maintenance can be performed very easily. Previously for common devices, this was only possible
with proprietary solutions and it typically required significant additional cabling work. With IO-Link,
down times caused by preventive maintenance or sudden breakdown of the equipment can be
reduced by 80% and problems can be detected much faster.
Miniaturization with IO-Link
Within recent years, a trend of smaller yet more powerful sensors and actuators can be seen in
process and factory automation. With IO-Link technology, it is easy to miniaturize products based on
these new devices using universally standardized and “intelligent” methods.
When using common proprietary solutions, especially those with high requirements for field bus
integrity, to design sensors with bi-directional communication and other “intelligent” features,
significantly more printed circuit board space is typically required and costs can be considerably
higher. The first IO-Link devices were assembled primarily using discreet components. Today highly
integrated microchips (cable driver ICs and microcontrollers) in very small packages of 3x5mm or
4x4mm or in wafer-level chip-scale package solutions (WL-CSP; see Fig. 1), with dimensions as small
as 2.5x2.5mm, enable powerful and cost-saving integration of IO-Link into the smallest intelligent
sensors and actuators. IC product families with the same pin count and size but different
functionality can support effective and easy platform designs for IO-Link applications.
Fig.1: IO-Link PHY IC as WL-CSP
The integration of IO-Link is relative easy, as demonstrated by the example of a block schematic for
an IO-Link sensor in Fig. 2. The IO-Link chip manufacturer and software provider very often support
the integration as well.
Fig. 2: Example block diagram for an IO-Link sensor
The standardized IO-Link interface enables the first production of intelligent, cost-saving and fieldbus-independent sensors and actuators at the lowest field level. It completes the “last meter”
between the field bus and sensors/actuators, enabling direct bi-directional communication between
the control station and the sensor or actuator device.
High-Precision Smart Sensors Via Innovative Signal Conditioning ICs
By Dr Marko Mailand (ZMDI)
November, 2012 in Technology First
Waveform Driven Plasticity in BiFeO3 Memristive Devices: Model and
Implementation
ByChristian Mayr, Paul Staerke, Johannes Partzsch, Rene Schueffny1; Love
Cederstroem2; Yao Shuai3; Nan Du, Heidemarie Schmidt4
2012 in Advances in Neural Information Processing Systems 25 (NIPS 2012)
Publisher: 2014 Neural Information Processing Systems Foundation, Inc.
Waveform Driven Plasticity in BiFeO3 Memristive
Devices: Model and Implementation
Christian Mayr, Paul Staerke, Johannes Partzsch, Rene Schueffny
Institute of Circuits and Systems
TU Dresden, Dresden, Germany
{christian.mayr,johannes.partzsch,rene.schueffny}@tu-dresden.de
Love Cederstroem
Zentrum Mikroelektronik Dresden AG
Dresden, Germany
[email protected]
Yao Shuai
Inst. of Ion Beam Physics and Materials Res.
Helmholtz-Zentrum Dresden-Rossendorf e.V.
Dresden, Germany
[email protected]
Nan Du, Heidemarie Schmidt
Professur Materialsysteme der Nanoelektronik
TU Chemnitz, Chemnitz, Germany
[email protected],[email protected]
Abstract
Memristive devices have recently been proposed as efficient implementations of
plastic synapses in neuromorphic systems. The plasticity in these memristive devices, i.e. their resistance change, is defined by the applied waveforms. This behavior resembles biological synapses, whose plasticity is also triggered by mechanisms that are determined by local waveforms. However, learning in memristive
devices has so far been approached mostly on a pragmatic technological level. The
focus seems to be on finding any waveform that achieves spike-timing-dependent
plasticity (STDP), without regard to the biological veracity of said waveforms or
to further important forms of plasticity. Bridging this gap, we make use of a plasticity model driven by neuron waveforms that explains a large number of experimental observations and adapt it to the characteristics of the recently introduced
BiFeO3 memristive material. Based on this approach, we show STDP for the
first time for this material, with learning window replication superior to previous
memristor-based STDP implementations. We also demonstrate in measurements
that it is possible to overlay short and long term plasticity at a memristive device
in the form of the well-known triplet plasticity. To the best of our knowledge, this
is the first implementations of triplet plasticity on any physical memristive device.
1
Introduction
Neuromorphic systems try to replicate cognitive processing functions in integrated circuits. Their
complexity/size is largely determined by the synapse implementation, as synapses are significantly
more numerous than neurons [1]. With the recent push towards larger neuromorphic systems and
higher integration density of these systems, this has resulted in novel approaches especially for the
synapse realization. Proposed solutions on the one hand employ nanoscale devices in conjuction
with conventional circuits [1] and on the other hand try to integrate as much synaptic functionality
(short- and long term plasticity, pulse shaping, etc) in as small a number of devices as possible. In
1
Institute of Circuits and Systems TU Dresden, Dresden, Germany
Zentrum Mikroelektronik Dresden AG, Dresden, Germany
3
Inst. of Ion Beam Physics and Materials Res., Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden, Germany
4
Professur Materialsysteme der Nanoelektronik, TU Chemnitz, Chemnitz, Germany
1
2
this context, memristive devices 1 as introduced by L. Chua [2] have recently been proposed as efficient implementations of plastic synapses in neuromorphic systems. Memristive devices offer the
possibility of having the actual learning mechanism, synaptic weight storage and synaptic weight
effect (i.e. amplification of the presynaptic current) all in one device, compared to the distributed
mechanisms in conventional circuit implementations [3]. Moreover, a high-density passive array
on top of a conventional semiconductor chip is possible [1]. The plasticity in these memristors,
i.e. their resistance change, is defined by the applied waveforms [4], which are fed into the rows
and columns of the memristive array by CMOS pre- and postsynaptic neurons [1]. This resembles biological synapses, whose plasticity is also triggered by mechanisms that are determined by
local waveforms [5, 6]. However, learning in memristors has so far been approached mostly on
a pragmatic technological level. The goal seems to be to find any waveform that achieves spiketiming-dependent plasticity (STDP) [4], without regard to the biological veracity of said waveforms
or to further important forms of plasticity [7].
Bridging this gap, we make use of a plasticity rule introduced by Mayr and Partzsch [6] which is
driven in a biologically realistic way by neuron waveforms and which explains a large number of
experimental observations. We adapt it to a model of the recently introduced BiFeO3 memristive
material [8]. Measurement results of the modified plasticity rule implemented on a sample device
are given, exhbiting configurable STDP behaviour and pulse triplet [7] reproduction.
2 Materials and Methods
2.1 Local Correlation Plasticity (LCP)
The LCP rule as introduced by Mayr and Partzsch [6] combines two local waveforms, the synaptic
conductance g(t) and the membrane potential u(t). Presynaptic activity is encoded in g(t), which
determines the conductance change due to presynaptic spiking. Postsynaptic activity in turn is signaled to the synapse by u(t). The LCP rule combines both in a formulation for the change of the
synaptic weight w that is similar to the well-known Bienenstock-Cooper-Munroe rule [9]:
dw
= B · g(t) · (u(t) − Θu )
(1)
dt
In this equation, Θu denotes the voltage threshold between weight potentiation and depression,
which is normally set to the resting potential. Please note that coincident pre- and postsynaptic
activities are detected in this rule by multiplication: A weight change only occurs if both presynaptic
conductance is elevated and postsynaptic membrane potential is away from rest.
The waveforms for g(t) and u(t) are determined by the employed neuron model. Mayr et al. [6] use
a spike response model [10], with waveforms triggered at times of pre- and postsynaptic spikes:
g(t) = Ĝ · e
−
t−tpre
n
τpre
u(t) = Up,n · δ(t − tpost
n ) + Urefr · e
−
pre
for tpre
n ≤ t < tn+1 ,
t−tpost
n
τpost
for tpost
≤t<
n
tpost
n+1
(2)
,
(3)
where
and
denote the n-th pre- and postsynaptic spike, respectively. The presynaptic conductance waveform is an exponential with height Ĝ and decay time constant τpre . The postsynaptic
potential at a spike is defined by a Dirac pulse with integral Up,n , followed by an exponential decay
with height Urefr (< 0) and membrane time constant τpost .
tpre
n
tpost
n
Following [6], postsynaptic adaptation is realised in the value of Up,n . For this, Up,n is decreased
from a nominal value Up if the postsynaptic pulse occurs shortly after another postsynaptic pulse:
−
Up,n = Up · (1 − e
post
−tn−1
tpost
n
τpost
)
(4)
The time constant for the exponential decay in this equation is the same as the membrane time
constant.
1
In 1971 Leon Chua postulated the existence of a device where the current or voltage is directly controlled
by voltage flux or charge respectively, this was called a memristor. Using a general state space description
Chua and Kang later extended the theory to cover the very broad class of memristive devices [2]. Even though
the two terms are used interchangeably in other studies, since the devices used in this study do not fit the strict
definition of memristor, we will refer to them as memristive devices in the following.
2
∆w in %
u in mV
g in nS
1.0
0.8
0.6
0.4
0.2
0.0
15
10
5
0
−5
−10
2.0
1.5
1.0
0.5
0.0
0
20
40
60
t in ms
80
100
120
Figure 1: Progression of the conductance g, the membrane potential u and the synapse weight w for
a sample spike pattern.
Figure 1 shows the pre- and postsynaptic waveforms, as well as the synaptic weight for a sample
spike train. For the simple waveforms, two principal weight change mechanisms are present: If
the presynaptic side is active at a postsynaptic spike, the weight is instantaneously increased by
the large elevation of the membrane potential. In contrast, all presynaptic activity falling into the
refractoriness period of the neuron (exponential decay after spike) integrates as a weight decrease.
As shown in [6], this simple model can replicate a multitude of experimental evidence, on par
with the most advanced (and complex) phenomenological plasticity models currently available. In
addition, the LCP rule directly links synaptic plasticity to other pre- and postsynaptic adaptation
processes by their influence on the local waveforms. This can be used to explain further experimental
results [6]. In Sec. 3.1, we will adapt the above rule equations to the characteristics of our memristive
device, which is introduced in the next section.
2.2
Memristive Device
Non-volatile passive analog memory has often been discussed for applications in neuromorphic
systems because of the space limitations of analog circuitry. However, until recently only a few
groups had access to sufficient materials and devices. Developments in the field of nano material
science, especially in the last decade, opened new possibilities for creating compact circuit elements
with unique properties.
Most notably after HP released information about their so-called Memristor [11] much effort has
been put in the analysis of thin film semiconductor-metal-metaloxide compounds. One of the commonly used materials in this class is BiFeO3 (BFO). The complete conducting mechanisms in BFO
are not fully understood yet, with partly contradictory results reported in literature, but it has been
confirmed that different physical effects are overlayed and dominate in different states. Particularly
the resistive switching effect seems promising for neuromorphic devices and will be discussed in
more detail. It has been shown in [12, 8] that the effect can appear uni- or bipolar and is highly
dependent on the processing regarding the substrate, growth method, doping, etc. [13].
We use BFO grown by pulsed laser deposition on Pt/Ti/SiO2 /Si substrate with an Au top contact,
see in Fig. 2. Memristors were fabricated with circular top plates, which were contacted with needle
probes, whereas the continuous bottom plate was contacted at one edge of the die. The BFO films
have a thickness of some 100nm. The created devices show a unipolar resistive switching with a
rectifying behavior. For a positive bias the device goes into a low resistive state (LRS) and stays
there until a negative bias is applied which resets it back to a high resistive state (HRS). The state
can be measured without influencing it by applying a low voltage of under 2V.
Figure 3 shows a voltage-current-diagram which indicates some of the characteristics of the device.
The measurement consists of three parts: 1) A rising negative voltage is applied which resets the
device from an intermediate level to HRS. 2) A rising voltage lowers the resistance exponentially.
3
Figure 2: Photograph of the fabricated memristive material that was used for the measurements.
3) A falling positive voltage does not affect the resistance anymore and the relation is nearly ohmic.
Because of the rectifying characteristic the current in LRS and HRS for negative voltages does not
exhibit as large a dynamic range as for positive voltages.
800
10−3
700
10−4
600
10−5
abs(I) in A
Im in uA
500
400
300
200
10−6
10−7
100
10−8
0
−100
−6
−4
−2
0
Vm in V
2
4
6
10−9−6
−4
−2
0
Vm in V
2
4
6
Figure 3: Voltage-current diagram of the device as linear and log-scale plot
2.3
Phenomenological Device Model
To apply the LCP model to the BFO device and enable circuit design, a simplified device model
is required. We have based our model on the framework of Chua and Kang [2]; that is, using an
output function (i.e., for current Im ) dependent on time, state and input (i.e., voltage Vm ). Recently,
this has been widely used for the modeling of memristive devices [11, 14, 15]. In contrast to many
memristive device models which are based on a sinh function for the output relationship (following
Yang et al. [14]), we model the BFO device as two semiconductor junctions. The junctions can
abstractly be described by a diode equation: Id = I0 (exp(qV /kT ) − 1) [16]. In an attempt to catch
the basic characteristics, our device could be modeled employing two diode equations letting a state
variable, x, influence the output and roughly represent the conductance:
(
)
(5)
Im = h(x, Vm , t) = I01 · (ed1 ·Vm (t) − 1) − I02 · (e−d2 ·Vm (t) − 1) · x(t)
where Vm is the voltage over the device2 and the diode like equations guarantee a zero crossing
hysteresis. The use of parameters I0i and di now allows individual control of current characteristics
for negative and positive voltages, and as shown in the previous section these are rather asymmetric
for our BFO devices. For the purpose of modeling plasticity, our focus has been on the dynamic
behavior of the conductance change; this was investigated in some detail by Querlioz et al. [15] and
has served as the basis for our model of the state variable:
dx
= f (x, Vm , t) = Γ(x) · Ψ(Vm )
dt
2
(6a)
With sinh(z) = 1/2 · (ez − e−z ), our approach is not fundamentally different from using a sinh function.
4
In the above the functions Γ(x) and Ψ(Vm ) relate to how the current state affects the state development and the effect of the applied voltage, respectively. Γ(x) is described by an exponential function.

x−Gmin

 e−β1 Gmax −Gmin , Vm (t) > 0,
Gmax −x
−β
(6b)
Γ(x) =
e 2 Gmax −Gmin , Vm (t) ≤ 0, x > Gmin ,


0,
else
In Ψ(Vm ) we again favor using separate exponential over sinh functions for increased controllability
of the different voltage domains (positive and negative). Here the parameters φ1 and φ2 govern the
voltage dependence of the state modification, with α1 and α2 scaling the result. With β1 and β2 , the
speed of state saturation is set:
(
)
{
α1 · (eφ1 Vm − 1 ,) Vm (t) ≥ 0,
Ψ(Vm ) =
(6c)
α2 · 1 − e−φ2 Vm , Vm (t) < 0,
For implementation, we have used one of the most prominent commercially available simulators
R
R
Spectre⃝
. Using befor custom analog and mixed-signal integrated circuit design, the Cadence⃝
havioral current sources, the equations for h(x, Vm , t) and f (x, Vm , t) can be implemented and
simulated with feasibility for circuit design. Depicted in Fig. 4 are the conductance change over
time, at different voltages, for model (Fig. 4a) and measurements (Fig. 4b). It can be seen how the
exponential dependency on device voltage gives rise to different levels of operation (Equations (5)
and (6c)). Also the saturation of conductance change for a given voltage is visible (Equation (6b)).
The sharp changes of current seen in the model are a result of our simplistic approach, whereas the
real devices show slower transitions. In addition, it can be noted that above 5 V the real device
appears to experience a significantly steeper rise in current. However, the target is to have reasonable characteristics in the region of operation below 5 V which is relevant in our plasticity rule
experiments.
6
5
Im in mA
1.2
1.0
4
0.8
3
0.6
0.4
20
30
t in s
40
50
60
6
5
1.0
4
0.8
3
0.6
0.4
2
0.2
1
10
Im (t)
Vm (t)
1.2
2
0.2
0.0
0
1.4
0.0
0
70
(a)
Vm in Volt
1.6
Im (t)
Vm (t)
Im in mA
1.4
Vm in Volt
1.6
1
10
20
30
t in s
40
50
60
70
(b)
Figure 4: Device current for different applied voltages for model (a) and measurement (b).
3
3.1
Results
Modified LCP
A nonlinearity or learning threshold is required in order to carry out the correlation operation
between pre- and postsynaptic waveforms that characterizes various forms of long term learning
[9, 17]. In the original LCP rule, this is done by the multiplication of pre- and postsynaptic waveforms, i.e. only coincident activity results in learning. Memristive devices are usually operated in
an additive manner, i.e. the pre- and postsynaptic waveforms are applied to both terminals of the
device, thus adding/subtracting their voltage curves. In order for the state of the memristive device
to only be affected by an overlap of both waveforms, a positive and negative modification threshold
is required [4]. As can be seen from equation 6c, the internal voltage driven state change Ψ(Vm )
is affected by two different parameters φ1 and φ2 which govern the thresholds for negative and
positive voltages. For our devices, these work out to effective modification thresholds of -2V and
5
Vpre in V
Vpost in V
−2
−1
0
1
2
Vpre-Vpost in V
4
2
0
−2
∆Im in %
2
1
0
−1
−2
50
40
30
20
10
0
0
20
40
60
t in ms
80
100
120
Figure 5: Modification of the original LCP rule for the BFO memristive device, from top to bottom:
pre- and postsynaptic voltages/waveforms, exponential decay with τpre resp. τpost (postsynaptic
waveform plotted as inverse to illustrate waveform function); resultant voltage difference across
memristive device and corresponding memristance modification thresholds (horizontal grey lines);
and memristance change as computed from the model of sec. 2.3
+2.3V. Thus, we need waveforms where coincident activity causes a voltage rise above the positive
threshold resp. a voltage drop below the negative threshold. In addition, we need a dependence
between voltage level and weight change, as the simplest method to differentiate between weights is
the voltage saturation characteristic in Fig. 3. That is, a single stimulus (e.g. pulse pairing in STDP)
should result in a distinctive memristive programming voltage, driving the memristive device into
the corresponding voltage saturation level via the (for typical experiments) 60 stimulus repetitions.
Apart from quantitative adjustments to the original LCP rule, this requires one qualitative adjustment. The presynaptic conductance waveform is now taken as a voltage trace and a short rectangular
pulse is added immediately before the exponential downward trace, arriving at a waveform similar
to the spike response model for the postsynaptic trace, see uppermost curve in Fig. 5. We call this
the modified LCP rule. For overlapping pre- and postsynaptic waveforms, the rectangular pulses of
both waveforms ’ride up’ on the exponential slopes of their counterparts when looking at the voltage
difference Vm = Vpre − Vpost across the memristive device for pre- and postsynaptic waveforms
applied to both terminals of the device (see third curve from top in Fig. 5). Since the rectangular
pulses are short compared to the exponential waveforms, they represent a constant voltage whose
amplitude depends on the time difference between both waveforms (as expressed by the exponential
slopes) as required above. Thus, as in the original LCP rule, the exponential slopes of pre- and postsynaptic neuron govern the STDP time windows. Repeated application of such a pre-post pairing
drives the memristive device in its corresponding voltage-dependent saturation level.
Similar to the original LCP rule, short term plasticity of the postsynaptic action potentials can now
be added to make the model more biologically realistic (e.g. with respect to the triplet learning
protocol [6]). We employ the same attenuation function as in equation 4, adjusting the duration of
the postsynaptic action potential, see second curve from top in Fig. 5.
Please note: One further important advantage of using this modified LCP rule is that both preand postsynaptic waveform are causal, i.e. they start only at the pre- respectively postsynaptic
pulse. This is in contrast to most currently proposed waveforms for memristive learning, i.e. these
waveforms have to start well in advance of the actual pulse [4], which requires preknowledge of a
pulse occurrence. Especially in an unsupervised learning context with self-driven neuron spiking,
this preknowledge is simply not existent.
6
120
100
80
60
60
40
40
20
0
20
0
−20
−20
−40
−40
−60
−80
−200
τpre=15ms, τpost=35ms
100
∆Im in %
∆Im in %
80
120
−60
−150
−100
−50
0
∆t in ms
50
100
150
−80
−200
200
−150
−100
−50
(a)
0
∆t in ms
50
100
150
200
(b)
Figure 6: Results for STDP protocol: (a) model simulation, (b) measurement with BFO memristive
device.
3.2
Measurement results
The waveforms developed in the previous section can be tested in actual protocols for synaptic plasticity. As a first step, we investigate the behaviour of the BFO memristive device in a standard
pair-based STDP experiment. For this, we apply 60 spike pairings of different relative timings at
a low repetition frequency (4Hz), comparable to biological measurement protocols [17]. Measurements were performed with a BFO memristive device as shown in Fig. 2. As shown in the model
simulations in Fig. 6a, the developed waveforms are transformed by the memristive device into
approx. exponentially decaying conductance changes. This is in good agreement with biological
measurements [17] and common STDP models [7]. The model results are confirmed in measurements for the BFO memristive device, as shown in Fig. 6b. Notably, the measurements result in
smooth, continuous curves. This is an expression of the continuous resistance change in the BFO
material, which results in a large number of stable resistance levels. This is in contrast e.g. to
memristive materials that rely on ferroelectric switching, which exhibit a limited number of discrete
resistance levels [18, 1]. Moreover, the nonlinear behaviour of the BFO memristive device has only
limited effect on the resulting STDP learning window. The resistance change is directly linked to
the applied waveforms. For example, as shown in Fig. 6, an increase in time constants results in correspondingly longer STDP time windows. Following our modeling approach, these time constants
are directly linked to the time constants of the underlying neuron and synapse model.
60
30
45
30
10
15
0
0
−10
−20
−15
−30
−30
−30
(a)
−20
0
−10
10
∆t2 t in ms
20
∆ Im in %
∆t1 in ms
20
30
(b)
Figure 7: Measurement results for the triplet protocol of Froemke and Dan [7]. (a) biological measurement data, adapted from [7], (b) measurement with BFO memristive device.
7
Experiments have shown that weight changes of single spike pairings, as expressed by STDP, are
nonlinearly integrated when occuring shortly after one another. Commonly, triplets of spikes are
used to investigate this effect, as carried out by [7]. The main deviation of these experimental results
compared to a pure STDP rule occur for the post-pre-post triplet [6], which can be attributed to
postsynaptic adaptation [7]. With this adaptation included in our waveforms (equation 4, as seen in
the action potential duration in the second curve from the top of Fig. 5), the BFO memristive device
measurements well resemble the post-pre-post results of [7]. The measurement results in Fig. 7b
show more depression than the biological data for the pre-post-pre triplet (upper left quadrant).
This is because changes in resistance need some time to build up after a stimulating pulse. In the
pre-post-pre case, the weight increase has not fully developed when it is overwritten by the second
presynaptic pulse, which results in weight decrease. This effect is dependent on the measured device
and the parameters of the stimulation waveforms (cf. Supplementary Material).
For keeping the stimulation waveforms as simple as possible, only postsynaptic adaptation has been
included. However, it has been shown that presynaptic short-term plasticity also has a strong influence on long-term learning [19, 6]. With our modeling approach, a model of short-term plasticity
can be easily connected to the stimulation waveforms by modulating the length of the presynaptic
pulse. Along the same lines, the postsynaptic waveform can be shifted by a slowly changing voltage
analogous to the original LCP rule (cf. Eq. 1) to introduce a metaplastic regulation of weight potentiation and depression [6]. Together, these extensions open up an avenue for the seamless integration
of different forms of plasticity in learning memristive devices.
3.3
Conclusion
Starting from a waveform-based general plasticity rule and a model of the memristive device, we
have shown a direct way to go from these premises to biologically realistic learning in a BiFeO3
memristive device. Employing the LCP rule for memristive learning has several advantages. As
a memristor is a two-terminal device, the separation of the learning in two waveforms in the LCP
rule lends itself naturally to employing it in a passive array of memristors [1, 4]. In addition, this
waveform-defined plasticity behaviour enables easy control of the STDP time windows, which is
further aided by the excellent multi-level memristive programming capability of the BiFeO3 memristive devices. There is only a very small number of memristors where plasticity has been shown at
actual devices at all [18, 1]. Among those, our highly-configurable, finely grained learning curves
are unique, other implementations exhibit statistical variations [1], can only assume a few discrete
levels [18] or the learning windows are device-inherent, i.e. cannot be adjusted [20]. This comes at
the price that in contrast to e.g. phase-change materials, BiFeO3 is not easily integrated on top of
CMOS [8].
The waveform-defined plasticity of the LCP rule enables the explicit inclusion of short term plasticity in long term memristive learning, as shown for the triplet protocol. As the pre- and postsynaptic
waveforms are generated in the CMOS neuron circuits below the memristive array [1], short term
plasticity can thus be added at little extra overall circuit cost and without modification of the memristive array itself. In contrast to our easily controlled short term plasticity, the only previous work
targeting memristive short term plasticity employed intrinsic (i.e. non-controllable) device properties [20]. To the best of our knowledge, this is the first time triplets or other higher-order forms of
plasticity have been shown for a physical memristive device.
In a wider neuroscience context, waveform defined plasticity as shown here could be seen as a
general computational principle, i.e. synapses are not likely to measure time differences as in naive
forms of STDP rules, they are more likely to react to local static [21] and dynamic [5] state variables.
Some interesting predictions could be derived from that, e.g. STDP time constants that are linked to
synaptic conductance changes or to the membrane time constant [22, 6]. These predictions could be
easily verified experimentally.
Acknowledgments
The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007- 2013) under grant agreement no. 269459 (Coronet).
8
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[15] D. Querlioz, P. Dollfus, O. Bichler, and C. Gamrat, “Learning with memristive devices: How should
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9
Subversion(r): Empirical Design Methodology from the Perspective of
Integrated Circuit Design
ByRadoslav Prahov, Holger Schmidt and Achim Graupner (ZMDI)
6. April 2013 in Institute of Research Engineers and Doctors
Publisher: Institute of Research Engineers and Doctors and SEEK Digital Library
Proc. of the Second Intl. Conf. on Advances in Electronics and Electrical Engineering — AEEE 2013
Copyright © Institute of Research Engineers and Doctors. All rights reserved.
ISBN: 978-981-07-5939-1 doi:10.3850/ 978-981-07-5939-1_11
Subversion(r): Empirical Design Methodology from
the Perspective of Integrated Circuit Design
Radoslav Prahov, Holger Schmidt and Achim Graupner
Dresden, Germany
{radoslav.prahov, holger.schmidt, achim.graupner}@zmdi.com
Although automated support for CMs has existed for over
thirty years, its prominence in the framework of IC design has
sharply increased during the last decade [4]. Early automated
support tools suffered from inadequate functionality and
applicability. In contrast, modern tools offer advanced utilities
and features [5]-[8]. Despite the evolution from simple tools to
comprehensive environments, automated support for the CM
is still confronted with challenges due to the advent of new
innovations and technologies [9]. One such challenge is the
ever-increasing complexity of IC projects [10]-[12]. For
instance, because of the more complex verification flows with
every new IC generation and process node, IC projects tend to
comprise ever-growing design data.
Abstract—An aspect of primary significance in integrated
circuit (IC) design is configuration management of design data,
i.e., the task of keeping a project comprising a multiplicity of
revisions well organized. Apache’s Subversion(r) is a software
tool that can facilitate this task. It manages revisions of
documentation, source code, and a wide variety of files, and it
automates storing and retrieving revisions. Unfortunately,
Subversion(r) provides insufficient support for IC projects
consisting of large numbers of managed items. We address this
problem by introducing, discussing, and demonstrating several
approaches that improve the performance of Subversion(r) when
handling a vast amount of files and directories. Our approaches
are division of the working copy into smaller pieces with a decent
granularity, conversion of the working copy into a single tarball
file, and implementation of a referred central working copy. Each
method is incorporated into the configuration management flow
through a lifecycle of IC development, which offers the
opportunity to compare and validate each technique.
As the most prominent CM tool, Apache’s Subversion®
(SVN) must respond to the trend toward more complex IC
designs with higher file counts. However, it has a deficit when
it comes to dealing with great numbers of managed items, as
its efficiency proportionally degrades with a growing quantity
of files and directories [13]-[15]. In addition to breaking a
tool’s environment, this leads to unacceptably long operation
times. Even in projects with average complexity, this is a
severe issue. In the majority of cases, the increased operation
time drags down productivity because the longer waiting time
cannot be used effectively. Reducing it not only accelerates
the IC design process, but also lowers the stress level for the
project’s IC developers.
Keywords—configuration management, Subversion, design
methodology, performance.
I.
Introduction
With the ongoing requirements for accomplishing higher
productivity and quality while ensuring effective control
before, throughout, and beyond the integrated circuit (IC)
development process, configuration management (CM) of
design data has become an important aspect of modern IC
projects. Its role is to assist designers by controlling, tracking
and coordinating every single change that occurs in the file
system during a project lifecycle by gathering evolutionary
revisions [1]. This allows users to perform unlimited updates
to the project information, but at the same time, they can be
assured that each user has the latest version. Users with an old
version have the ability to either update their working copy to
the most recent version or continue employing their old one
and propagate their changes afterwards. Conversely, users
with a head version (the version presently designated as most
current) can check out a previous version; for example, for
comparison if anything regresses. Changes during IC projects
could have a diverse character. Beyond basic file
modifications, they may also involve adding, removing, or
updating directories; modifying the hierarchy; altering group
permission and file and directory ownership; and renaming
files and directories [2],[3].
The present study was designed to evaluate different
approaches that could adapt SVN to handling a vast quantity
of files and directories more efficiently. The approaches were
incorporated into the CM and were employed during the
lifetime of an IC design project. The effect on SVN is
compared, and the improvement is defined in this study.
The remainder of this paper is organized as follows. In
section II, a concise evolutionary history and features of SVN
are introduced, related work is presented, and challenges of
migrating from one CM tool to another are identified. This is
followed by section III, where the problem of controlling a
multiplicity of files and directories is addressed, different
design methodology techniques that allow SVN performance
improvement are presented, and their implications for the
integrated circuit workflow architecture and revision control
system are discussed. Section IV explains the industrial
project into which the design methodologies were
16
ISBN: 978-981-07-5939-1 doi:10.3850/ 978-981-07-5939-1_11
parental relations are not naturally represented in the
repository tree structure. However, compared to most common
distributed version control systems, several merging issues
still remain ([18], cf. Chapter 4).
incorporated and presents an evaluation and discussion.
Section V concludes the paper.
II.
Background
Since the advent of Concurrent Versions System (CVS),
initially as a set of shell scripts coded by Dick Grune (1986)
and later converted to a C program by Brian Berliner (1989)
[16], CVS has become one of the most prominent version
control tools, widely employed in various projects. Even now,
over two decades later, it is the second most widespread tool
in terms of market share (13%) [17]. During this extensive
period of development and usage, its benefits were identified;
however, substantial problems emerged. Hence in 2000, a
group including former CVS developers launched SVN, a
version control tool explicitly intended to be a successor of
CVS with a similar design and improved functionality [18]. Its
first official release arrived in 2004. At present, SVN is the
most widespread version control tool, with a market share of
51% [17].
A.
B.
Problem Statement
Despite SVN’s dominant market share and improved
functionality, SVN often suffers from a performance
deficiency when it handles a multiplicity of managed items.
This is not actually recent news, nor an exclusive trait of SVN,
since the signs were first observed in ancestral CVS. In 1989,
prolonged times were recorded while CVS managed the
Prisma™ project by Prisma, Inc., which comprised over
17,000 files [19].
Subsequently the effect of escalated IC project complexity
upon the behavior of SVN was assessed in [13]-[15]. How the
system can be adapted to a multitude of files with a different
origin was presented in [14] by investigation of several typical
user cases. SVN performance limitations and suggestions for
how they can be overcome were also discussed. When
investigating sources of bottlenecks in SVN, the most
significant finding was the relationship between the number of
managed items and the execution time of SVN operations.
Furthermore, the relationship is quadratic for commit
commands and linear for add/checkout commands.
SVN
SVN’s repository core is the storage backend where all
versioned data are stored. Each time a client successfully
commits certain changes, the SVN repository creates a new
snapshot of the versioned file-system tree, called a revision or
version. An increasing, unique number globally identifies each
version. The snapshot contains the revision directory structure,
file meta-data, and file contents, which might be delta
compressed to save space. The delta compression keeps only
the differences between successive versions of files. To
retrieve a specific file revision, SVN composes a sequence of
deltas up to the last full version. Because searching through all
file revisions is time-consuming, full versions called skipdeltas are inserted between deltas.
Taking into account all findings and results of the studies
mentioned above, the optimum effectiveness of SVN can be
achieved by keeping project data compact and locating the
repository and working copy in a RAM disk on a sufficiently
powerful machine with an adequately spacious cache area.
However, with the ongoing growth of IC project complexity,
the reduction of design data is hardly applicable. Even though
hosting the repository and working copies in a RAM disk has
proven to be the most efficient configuration [14], in our view,
it remains a theoretical technique with limited possibility of
application because in a considerable proportion of cases, the
required allocation of space is substantial. Furthermore,
implementing mandatory security measures, such as backup
and regular snapshots, is more complex. Another setback is
that job distribution techniques, such as using a load-shared
facility (LSF), which is widespread, cannot be employed.
On the client side, for each file in the working copy, a
pristine copy, the revision number (on which the local file is
based), and the timestamp of its last update are stored. The
pristine copy allows using several commands without any
repository interaction: checking file status, comparing files
with their unmodified version (svn diff) and restoring contents
(svn revert). Committing changes from the client’s working
copy to the repository does not trigger a synchronization of
other locally unmodified files. Thus, after committing a subset
of the working copy, it is left in a mixed-revision state;
therefore, the base revision number must be tracked for every
file and directory. To reproduce all upstream changes, the svn
update command pulls all changes, optionally only up to a
specified revision. Local modifications are automatically
reintegrated, and the usual conflict-resolution workflow is
applied.
Regardless of the flaws discussed above, a substitution of
the CM tool is often not an alternative and is hardly applicable
because of the CM’s tight integration into the design
workflow. For instance, in the project for Apache Software
Foundation’s OpenOffice™ (for which the repository
consisted of over 66,000 files), it was reported that various
tools and wrapper scripts, such as issue tracking,
authentication, and some tools specific to the project (EIS,
LION, etc.), had to be entirely redesigned [20]. Furthermore,
programs that were supplementary to the IC development
process (such as tools facilitating the design and SoC project
management and the GUI support tools) are only compatible
with specific CM tools, usually SVN and Perforce™
(trademark of Perforce Software, Inc.). Hence, in this work,
we address the SVN bottleneck and propose three approaches
that are capable of mitigating the SVN dependence on the
amount of managed items.
SVN supports branching, merging, and tagging using an
additional directory layer in the repository hierarchy; typically,
main development happens in the trunk, while development of
branches and tagged versions reside in corresponding named
directories. Since version 1.5 (2008), merge information is
automatically stored in the path meta-data (svn:merginfo).
This simplifies merging between branches and the trunk, as
17
ISBN: 978-981-07-5939-1 doi:10.3850/ 978-981-07-5939-1_11
Design Methodology
UNIXgzip command. Conversely, when the uploaded file has
to be accessed, it must also be decompressed. Due to the
compressed character of the block, an additional speed boost
and shrinkage of the space that is consumed on the server are
observed.
In the following section, three different techniques are
presented as each of them allows reducing the quantity of files
and directories that SVN handles per operation.
A.
Since in [14] both principles were proven to be efficient,
not only for binary files, but also for a wide range of file
formats, the latter approach was implemented in the IC project
as shown in Fig. 4. The tar/compress and untar/decompress
steps were entirely automated due to their routine and
particularly error prone character.
Division of the Working Copy into
Smaller Pieces with a Decent
Granularity (DM1)
The first proposal is based on division of the working copy
into smaller pieces with a decent granularity, organized in a
block-based hierarchy. In such a structure, each block can be
processed individually in parallel. In addition to parallelizing
the operations, this allows reducing the number of files to be
manipulated (submitted/updated) at once.
+|
|
|
|
|
|
|
|
|
|
Putting this approach into practice can be achieved by
different methods. One method would be to divide the project
into as many various unit types as possible. A unit type
constitutes a heterogeneous, separate design part; for example,
a directory of a circuit block or sub-block. Different unit types
are generally limited by the character of the project data.
Therefore, a detailed verification under the project hierarchy
and design data might be needed for such architecture.
Figure 1. Classical structure of analog library
We chose to divide the data as shown in Fig. 1 and Fig. 2.
Since IC designs possess a decent granularity by nature, the
analog library depicted is suitable for dividing into its
heterogeneous subdirectories (bandgap, oscillator, and vref).
However, the effort of reorganizing existing projects should be
taken into consideration. Even so, this is one of the focal
advantages of the approach since the method can be employed
directly out-of-the-box for a substantial portion of IC designs.
B.
analog_library
+- bandgap
+- bandgap_resistors
+- bandgap_amplifier
+- tb_bandgap
+- oscillator_20kHz
+- oscillator_trimunit
+- oscillator_schmitttrigger
+- tb_oscillator
+- vref_18
+- …
+|
|
|
|
+|
|
|
|
+|
+-
Conversion of the Working Copy into
a Single Tarball File (DM2)
bandgap_library
+- bandgap
+- bandgap_resistors
+- bandgap_amplifier
+- tb_bandgap
oscillator_20kHz_library
+- oscillator_20kHz
+- oscillator_trimunit
+- oscillator_schmitttrigger
+- tb_oscillator
vref_18_library
+- vref_18
+- …
Figure 2. Organization of analog library into smaller pieces with decent
granularity. Below level 1, each subfolder could be manipulated in isolation.
The basic principle of the approach introduced in [13] and
[14] is depicted in Fig. 3. The quantity of managed files and
directories is decreased by combining them into a tarball
archive, which accelerates SVN. Initially, this principle was
only proposed for binary files, for which the number of files
can be efficaciously reduced by two mutually complementary
means [13]. In the first case, the whole directory structure is
converted into one single monolithic block. For that purpose,
data that are to be imported into the repository are transformed
into one file via a simple tar operation and then the tar file is
uploaded to the repository. When the data must be accessed
(updated), the tar file is untarred and they are again available.
Since the revision control system is facilitated and does not
need to recursively deal with the initial directory structure, but
rather with just a single block, an acceleration of about 15
times was reported [13].
Files
Project
Repository
Files.tar
Project
Repository
Execution time
III.
1x
15x
Files.tar.gz
Project
Repository
The second method takes the first case a step further by
compressing the single block. The process is essentially the
same, except that the tar file is compressed before being
uploaded to the repository. This could be done in various
ways; albeit, a simple and effective one is the standard
19x
Figure 3. Three techniques for importing into the SVN repository: plain file
structure, simple tar file, and compressed tar file, with respective performance.
18
ISBN: 978-981-07-5939-1 doi:10.3850/ 978-981-07-5939-1_11
developed by a single engineer but at the same time is
referenced by others. Since a significant proportion of
elements in the user’s working space is not modified and not
directly employed (but elements still need to be referenced),
the elements can be referred to the central working copy
through soft links, whereas all developed elements remain in
the regular working copy.
Files
tar
compress
untar
decompress
Files.tar.gz
commit
Implementation of the structure presented above is
illustrated in Fig. 5. It consists of a three-level hierarchy,
adding an additional level to the conventional server-client
configuration traditionally employed by the revision control
system.
update
Project
Repository
Importing (checking in) the design data to the repository is
performed with the standard method; i.e., the new structure
does not affect this process at all. When the data are to be
checked out, instead of being transferred directly from the
server to the client, they are initially copied onto a central
replication area and then the workspace is created. Each unit
from the workspace could either point to the replication area
as a soft link or could be represented physically. Soft links
have read-only access because blocks that are in the
replication area cannot be modified. If modification is
required, they must be transferred to the local workspace first.
Each block can be converted at any time, replacing a link with
local data and vice versa. The replication area cannot be
updated (for fixed revisions) in terms of replacing an old
version of a block with a newer one, but it can comprise more
than one revision of a certain block. Of course, all outdated
block versions could be removed once they are no longer
required. From the methodology description up to this point, it
could be inferred that the replication area behaves as a typical
second server, except that its data do not require being backed
up, as they can readily be recovered at any given moment and
they do not contain any modifications.
Figure 4. Details of compressed tar file approach.
The first step was carried out in the sequence:

Directory existence verification. This step verifies that
the directory that was selected to be manipulated
exists. If not, the sequence is terminated.

SVN management validation. Whether or not the
specified directory is already managed by SVN is
validated. If SVN managed, the directory must be
erased from the SVN repository.

Tar file existence verification. This step verifies
whether a tar file with an identical name exists. If so,
its content is compared against the specified directory.
If they are equivalent, the sequence is discontinued.
Otherwise, the step is executed and the tar file is either
brought into existence or updated.
The next step, untar/decompress, is executed on the
algorithm:

Tar file update verification. Whether the tar file has
already been updated in the local directory structure is
verified. If not, the algorithm is terminated.

SVN management validation. This step validates
whether the directory included in the tar file has
already been managed by SVN. If it is, the algorithm
is discontinued.

Workspace tar content SVN management verification.
If the directory already exists in the user’s workspace
but it is not managed by SVN, it is automatically
removed. Next, the tar file is extracted.
This approach has the prerequisites of block-oriented
design data structure and decent granularity, as discussed
previously for Fig. 2. This method smoothly allows each block
to be fetched into the working copy either as a soft link or as
physical data. For instance, blocks that are never employed
could be referred to the central working copy, whereas all the
others would remain part of the regular working space. This
measure also allows parallel processing and saves disk space.
The linked central working copy technique can be
implemented with different methods. One is to develop
proprietary scripts. However, especially in the field of IC
design, this tends to be limited by the ability of the
programmers who develop and maintain them (might lack
training or experience and might not be diligent). Furthermore,
scripts are relatively insufficiently flexible, and even a slight
environment alteration could trigger discrepancies and
inconsistencies, which are difficult to fix. Therefore, we chose
a tool available on the market for implementing the technique:
Methodics’ BuildICTM. It is an SoC assembly engine, part of a
platform for SoC design management [21]. However, we
consider it to be also beneficial for workspace management, as
it has a “shared area,” which has the identical functionality as
the replication area.
The application of the automated transformation of the
initial data structure into a monolith block is not only to allow
eliminating all trivial tasks, but also to keep this relatively
error-prone phase protected.
C.
Referred Central Working Copy
(DM3)
This approach differs from the others in that it involves
maintaining a central working copy for read-only access. A
data unit being designed within an IC project is generally
19
ISBN: 978-981-07-5939-1 doi:10.3850/ 978-981-07-5939-1_11
Workspace
Replication area
Repository
Block A r/w
Block A
Block A
Block B r/o
Block B.revX
Block B
Block C r/o
Block C.revY
Block C
Figure 5. Schematic of the referred central working copy approach. Blocks that are not required in the user’s workspace are referred to the central working copy.
IV.
suitable for tar and untar because of the infrequency of
modifications to them.
User Case
Another hurdle is the extra step of transforming the initial
data into a single block. This should be considered a critical
phase, due to its routine and error prone character. A possible
solution is an automation of the process of handling the data
with a wrapper script. Although application of the automation
script mitigates the problem, it should still be considered
critical. By presumption, any directory with a name equivalent
to the content of the tar file is deleted because we determine
that by and large, it is left from any preceding execution;
however, the folder might contain important, modified, but not
yet committed project data as well. Moreover, due to the
development and maintenance of scripts, a further level of
complexity is added to the project design flow.
The design methodologies that were described in the
previous section were incorporated into the CM workflow of
our ZSPM1000 Smart Power Management (SPM) IC project.
The ZSPM1000 is a configurable, true-digital single-phase
pulse-width-modulation (PWM) controller for high-current,
non-isolated DC/DC power supplies supporting switching
frequencies up to 1 MHz. It includes a PMBus™-configurable
digital power control loop that incorporates output voltage
sensing, average inductor current sensing, and extensive fault
monitoring and handling options. Project data comprised 48
blocks with a total of 50,000 files and a total size of 5.9GB.
A.
DM2
Initially, DM2 was implemented from the foundation of
the project. According to the design team, this principle
allowed them to solve the SVN performance limitations;
however, the improved efficiency comes at a cost. The
application of SVN on a file level is not possible. Standard
features of revision control systems, such as file history,
revert, selective checkout and locking functionalities, are not
available.
B.
DM3 and DM1
Due to the drawbacks identified in DM2, an alternative
combined DM3 and DM1 CM workflow was integrated into
the ZSPM1000 project. The workflow achieves an improved
performance compared with DM2. This can be explained by
the parallel algorithm in which operations are performed.
When the same operation is executed in a sequential
manner, the replication area is only composed during the first
execution and reused later. Hence, the most rapid execution
time is achieved when the replication area has already been
brought into existence because of the minimal time that is
required for establishing soft links.
Furthermore, changes between different revisions are not
traceable. For example, the following fundamental questions
for revision control systems cannot be answered. Which files
were changed? Who made the change? What was changed in
the file? What did the file contain in a particular revision? All
difference comparison futures are inevitably lost. The
graphical user interface support, which is one of the focal
advantages of SVN, is no longer efficacious.
In contrast, if the replication area does not already exist
and all units are required to be available in a local workspace,
the longest time is needed. However, in this project
experience, only a small number of blocks were required in
the users’ workspace for write access (locally). This reflects a
dedicated designer who needs to reference all blocks during a
project lifetime but modifies only a minority of them.
In our efforts to address these issues, a policy of extensive
commit messages was put in force. Nonetheless, we rapidly
came to realize that this hardly helps when design teams are
spread over different locations. Even so, in our experience, the
issue can be avoided if an intellectual property (IP) project
design is employed. An IP constitutes a standard functional
block that is part of the IC but was developed separately from
the project either internally or sourced by a third party. During
the design phase, IP blocks are immutable. As such, they are
The improved performance is explained by the reduced
quantity of items that SVN handles (during checkout) per
operation and also by the parallel manner in which the
commands are executed. Furthermore, the establishment of
links is performed in very little time. It should be noted that in
20
ISBN: 978-981-07-5939-1 doi:10.3850/ 978-981-07-5939-1_11
developed by a single engineer but at the same time is
referenced by others. Since a significant proportion of
elements in the user’s working space is not modified and not
directly employed (but elements still need to be referenced),
the elements can be referred to the central working copy
through soft links, whereas all developed elements remain in
the regular working copy.
Files
tar
compress
untar
decompress
Files.tar.gz
commit
Implementation of the structure presented above is
illustrated in Fig. 5. It consists of a three-level hierarchy,
adding an additional level to the conventional server-client
configuration traditionally employed by the revision control
system.
update
Project
Repository
Importing (checking in) the design data to the repository is
performed with the standard method; i.e., the new structure
does not affect this process at all. When the data are to be
checked out, instead of being transferred directly from the
server to the client, they are initially copied onto a central
replication area and then the workspace is created. Each unit
from the workspace could either point to the replication area
as a soft link or could be represented physically. Soft links
have read-only access because blocks that are in the
replication area cannot be modified. If modification is
required, they must be transferred to the local workspace first.
Each block can be converted at any time, replacing a link with
local data and vice versa. The replication area cannot be
updated (for fixed revisions) in terms of replacing an old
version of a block with a newer one, but it can comprise more
than one revision of a certain block. Of course, all outdated
block versions could be removed once they are no longer
required. From the methodology description up to this point, it
could be inferred that the replication area behaves as a typical
second server, except that its data do not require being backed
up, as they can readily be recovered at any given moment and
they do not contain any modifications.
Figure 4. Details of compressed tar file approach.
The first step was carried out in the sequence:

Directory existence verification. This step verifies that
the directory that was selected to be manipulated
exists. If not, the sequence is terminated.

SVN management validation. Whether or not the
specified directory is already managed by SVN is
validated. If SVN managed, the directory must be
erased from the SVN repository.

Tar file existence verification. This step verifies
whether a tar file with an identical name exists. If so,
its content is compared against the specified directory.
If they are equivalent, the sequence is discontinued.
Otherwise, the step is executed and the tar file is either
brought into existence or updated.
The next step, untar/decompress, is executed on the
algorithm:

Tar file update verification. Whether the tar file has
already been updated in the local directory structure is
verified. If not, the algorithm is terminated.

SVN management validation. This step validates
whether the directory included in the tar file has
already been managed by SVN. If it is, the algorithm
is discontinued.

Workspace tar content SVN management verification.
If the directory already exists in the user’s workspace
but it is not managed by SVN, it is automatically
removed. Next, the tar file is extracted.
This approach has the prerequisites of block-oriented
design data structure and decent granularity, as discussed
previously for Fig. 2. This method smoothly allows each block
to be fetched into the working copy either as a soft link or as
physical data. For instance, blocks that are never employed
could be referred to the central working copy, whereas all the
others would remain part of the regular working space. This
measure also allows parallel processing and saves disk space.
The linked central working copy technique can be
implemented with different methods. One is to develop
proprietary scripts. However, especially in the field of IC
design, this tends to be limited by the ability of the
programmers who develop and maintain them (might lack
training or experience and might not be diligent). Furthermore,
scripts are relatively insufficiently flexible, and even a slight
environment alteration could trigger discrepancies and
inconsistencies, which are difficult to fix. Therefore, we chose
a tool available on the market for implementing the technique:
Methodics’ BuildICTM. It is an SoC assembly engine, part of a
platform for SoC design management [21]. However, we
consider it to be also beneficial for workspace management, as
it has a “shared area,” which has the identical functionality as
the replication area.
The application of the automated transformation of the
initial data structure into a monolith block is not only to allow
eliminating all trivial tasks, but also to keep this relatively
error-prone phase protected.
C.
Referred Central Working Copy
(DM3)
This approach differs from the others in that it involves
maintaining a central working copy for read-only access. A
data unit being designed within an IC project is generally
19
ISBN: 978-981-07-5939-1 doi:10.3850/ 978-981-07-5939-1_11
Workspace
Replication area
Repository
Block A r/w
Block A
Block A
Block B r/o
Block B.revX
Block B
Block C r/o
Block C.revY
Block C
Figure 5. Schematic of the referred central working copy approach. Blocks that are not required in the user’s workspace are referred to the central working copy.
IV.
suitable for tar and untar because of the infrequency of
modifications to them.
User Case
Another hurdle is the extra step of transforming the initial
data into a single block. This should be considered a critical
phase, due to its routine and error prone character. A possible
solution is an automation of the process of handling the data
with a wrapper script. Although application of the automation
script mitigates the problem, it should still be considered
critical. By presumption, any directory with a name equivalent
to the content of the tar file is deleted because we determine
that by and large, it is left from any preceding execution;
however, the folder might contain important, modified, but not
yet committed project data as well. Moreover, due to the
development and maintenance of scripts, a further level of
complexity is added to the project design flow.
The design methodologies that were described in the
previous section were incorporated into the CM workflow of
our ZSPM1000 Smart Power Management (SPM) IC project.
The ZSPM1000 is a configurable, true-digital single-phase
pulse-width-modulation (PWM) controller for high-current,
non-isolated DC/DC power supplies supporting switching
frequencies up to 1 MHz. It includes a PMBus™-configurable
digital power control loop that incorporates output voltage
sensing, average inductor current sensing, and extensive fault
monitoring and handling options. Project data comprised 48
blocks with a total of 50,000 files and a total size of 5.9GB.
A.
DM2
Initially, DM2 was implemented from the foundation of
the project. According to the design team, this principle
allowed them to solve the SVN performance limitations;
however, the improved efficiency comes at a cost. The
application of SVN on a file level is not possible. Standard
features of revision control systems, such as file history,
revert, selective checkout and locking functionalities, are not
available.
B.
DM3 and DM1
Due to the drawbacks identified in DM2, an alternative
combined DM3 and DM1 CM workflow was integrated into
the ZSPM1000 project. The workflow achieves an improved
performance compared with DM2. This can be explained by
the parallel algorithm in which operations are performed.
When the same operation is executed in a sequential
manner, the replication area is only composed during the first
execution and reused later. Hence, the most rapid execution
time is achieved when the replication area has already been
brought into existence because of the minimal time that is
required for establishing soft links.
Furthermore, changes between different revisions are not
traceable. For example, the following fundamental questions
for revision control systems cannot be answered. Which files
were changed? Who made the change? What was changed in
the file? What did the file contain in a particular revision? All
difference comparison futures are inevitably lost. The
graphical user interface support, which is one of the focal
advantages of SVN, is no longer efficacious.
In contrast, if the replication area does not already exist
and all units are required to be available in a local workspace,
the longest time is needed. However, in this project
experience, only a small number of blocks were required in
the users’ workspace for write access (locally). This reflects a
dedicated designer who needs to reference all blocks during a
project lifetime but modifies only a minority of them.
In our efforts to address these issues, a policy of extensive
commit messages was put in force. Nonetheless, we rapidly
came to realize that this hardly helps when design teams are
spread over different locations. Even so, in our experience, the
issue can be avoided if an intellectual property (IP) project
design is employed. An IP constitutes a standard functional
block that is part of the IC but was developed separately from
the project either internally or sourced by a third party. During
the design phase, IP blocks are immutable. As such, they are
The improved performance is explained by the reduced
quantity of items that SVN handles (during checkout) per
operation and also by the parallel manner in which the
commands are executed. Furthermore, the establishment of
links is performed in very little time. It should be noted that in
20
ISBN: 978-981-07-5939-1 doi:10.3850/ 978-981-07-5939-1_11
The work reported in this study was funded by the Seventh
Framework Program of the EC under grant agreement no.
237955 (FACETS-ITN).
contrast to the tar-untar approach, all benefits of the revision
control system are preserved, which is a key asset of this
mixed technique.
Several inconveniences were explored during the lifetime
of the project however. Because of DM1, it is not possible to
use a single operation to atomically commit multiple blocks
that have been modified with related refinements because each
block must be managed separately (Fig. 3). It was reported by
the design team that although this slightly affects the revision
control tool history by adding further revision numbers for
each manipulation, it does not influence the workflow.
Additional feedback confirmed that the application of this
technique leads to significant performance improvement and
reduction of the amount of data per operation.
References
[1]
[2]
[3]
[4]
[5]
The replication area in DM3 does not particularly affect
the IC design workflow. It is not a critical element and does
not require any special maintenance measures. Even though
this area might be considered to consume extra disk space, it
actually saves space because the user’s working copies are
reduced in size. The central working copy can be updated
automatically by a post-commit script.
[6]
[7]
[8]
Nonetheless, the disadvantage of the automatic updating
mechanism is the alteration of files without prior notice; for
example, when a designer refers to a head revision of a given
block and that block has changed. As a result, the designer
would automatically be referred to the new head revision.
However, in addition to the discomfort of unexpected changes
in the working copy structure, this can lead to breaking the
environment; e.g., regressions and debug sessions, which
count on stable data. Hence, we chose to set up links to the
central working area for fixed revisions and to update them
when required.
V.
[9]
[10]
[11]
[12]
Summary and Future Work
[13]
This paper has presented three different approaches that
adapt the CM tool Subversion® to dealing with a multiplicity
of managed items. Since each of the proposed approaches was
ingrained in an industrial IC project flow from “scratchpad” to
the final product, they were compared and validated in a
realistic environment.
[14]
[15]
The demonstrated methods will be particularly beneficial
in future IC design projects for which the revision control tool
would be stretched to its breaking point with the increased
quantity of project data.
[16]
[17]
Thus far we have mainly explored the design mythology
from the user’s perspective. Our next step in this research will
be to perform a performance case study. We are interested in
comparing the performance improvement of each technique.
[18]
[19]
[20]
[21]
Acknowledgment
The authors wish to thank the design team for the
ZSPM1000 project at ZMD AG for their technical assistance
and feedback during the lifetime of the project as well as Ms.
M. Wallace and Mr. D. Aitken for proofreading the
manuscript.
21
828-2012 – IEEE Standard for Configuration Management in Systems
and Software Engineering, March 2012.
C. Kidd, “The case for configuration management,” IEE Review, vol.
47, pp. 37-41, September 2001.
K. Hinsen, K. Läufer, and G. Thiruvathukal, “Essential tools: version
control systems,” IEEE Computer in Science & Engineering, vol. 11,
pp. 84-91, November-December 2009.
M. Rochkind, “The source code control system,” IEEE Transactions on
Software Engineering, vol. 4, pp. 364-370, December 1975.
K. H. Lee, “Design and implementation of a configuration management
system,” Global Telecommunications Conference, vol. 3, pp.1563-1567,
November-December 1993.
A. Do, “The impact of configuration management during the software
product's lifecycle,” Digital Avionics Systems Conference, vol. 1,
pp. 1.A.4-1 – 1.A.4-8, November 1999.
A. Chan and S. Hung, “Software configuration management tools,”
Software Technology and Engineering Practice, pp. 238-250, July 1997.
H. Yue, X. Liu, and S. Zhao, “Evaluate two software configuration
management tools: MS Perforce and Subversion,” Computational
Intelligence and Software Engineering, pp. 1-6, December 2010.
D. Kim and C. Youn, “Traceability enhancement technique through the
integration of software configuration management and individual
working environment,” Secure Software Integration and Reliability
Improvement, pp. 163-172, June 2010.
X. Wang, W. Chen, Y. Wang, and H. You, “The design and implementation of hardware task configuration management unit on
dynamically reconfigurable SoC,” Embedded Software and Systems,
ICESS '09, pp. 179-184, May 2009.
M. Mehendale, “SoC – the road ahead,” IEEE VLSI Design, January
2006.
J. Burns, “Technology trends and implications on SoC design,” IEEE
SoC Conference, pp. 386, September 2011.
D. Bell, “Performance tuning Subversion,” IBM developerWorks, May
2007, accessed August 2012 http://www.ibm.com/developerworks/java/
library/j-svnbins/index.html.
R. Prahov, H. Schmidt, E. Müller, and A. Graupner, “Subversion(r): an
Empirical Performance Case Study from a Collaborative Perspective on
Integrated Circuits and Software Development,” ICSESS, in press.
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from the Perspective of Integrated Circuit Design,” IEEE 27th
Convention of Electrical and Electronic Engineers in Israel, pp. 1-5,
November 2012.
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accessed August 2012, http://ximbiot.com/cvs/manual/, 2005.
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B. Collins-Sussman, B. Fitzpatrick, and C. Pilato, “Version Control with
Subversion” (for Subversion 1.7), 2011, http://svnbook.red-bean.com/.
B. Berliner, “CVS II: Parallelizing software development”, USENIX
Winter 1990 Technical Conference, pp. 341–352, 1990.
The OpenOffice™ project, http://www.openoffice.org/.
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August 2012, http://www.methodics-da.com/products/projectic.
What‘s Behind Digital Power
by Herman Neufeld (ZMDI)
May 1st, 2013, Electronic Products (USA)
1 Energy-Saving Initiative
SPonSored By
an electronic products special series
What’s Behind Digital Power
Control?
By Herman neufeld
Senior member of the Technical Staff
at ZmdI
[email protected]
l
ike any new technique that is
introduced in the market, digital
power control must first prove
that it offers important advantages over
state-of-the-art analog techniques. In this
vein, the first and foremost issue to be
addressed is the price, and the secondary
considerations are converter size, performance and efficiency. This article covers
these issues and also discusses digital
power control from a broad standpoint.
What is digital power?
digital power, as the term implies, is a
technique used for converting power via
digital control means. Instead of using
analog components, such as operational
amplifiers and comparators, it uses a
digital controller. Both control techniques
are designed to ensure that the power
stage switches at the right moment in
every switching cycle in order to properly
regulate the output voltage. deviations
from the correct switching instant lead to
deteriorating performance, instabilities,
and in extreme cases to malfunction of
the load that is being powered. Therefore,
performance—not just price—should be
something to closely consider. In fact,
one of the major differentiators between
digital and analog power control is
performance.
Cost
for the typical power supply designer,
analog technology has been proven
to deliver good and efficient power
converters. So why change? Why spend
more money on a digital controller?
What is clearly overlooked here is that
not all converter applications require
a digital controller. Take, for example,
a converter that is required to produce
5 V at 1 a. In this case, analog control is the best choice—a conclusion
based purely on price. There are also
many analog controllers available on
the market. as a rule of thumb, one
could state that analog control is the
preferred choice for converters with
output voltages above 3 V and currents
below 10 a. digital controllers are not
meant to compete against these analog
controllers, especially when price is
important and analog performance is
the settings on the controller and issue
PmBus commands to change them. The
equivalent of an aSIC can also be realized
by modifying the firmware in order to
meet the customer’s needs. This, however,
is done by the IC manufacturer. The cost
savings compared to an analog aSIC are
achieved because the IC itself does not
change.
further reductions in cost can be
achieved via a fully automated production
process that is possible with a digital controller. The converter can be programmed,
Fig. 1: Configuration setup for the ZSPM1000 digital controller.
perfectly adequate for the application.
However, for a fast-growing market of
servers, routers, switches and embedded
controls, the converters that power these
applications require a much higher level
of performance than analog controllers
can offer. loads such as field-programmable gate arrays (fPGas), processors,
memory banks and similar digital blocks
need to interact with the converter feeding them. analog controllers with a digital
interface are also available on the market,
but, they are not as flexible as digital controllers when requirements change. aSICs
also require development time and cost.
With a digital controller, such as ZmdI’s
ZSPm1000, the user is able to configure
MAY 2013 • electronicproducts.com • ElEctronic Products
tested, and calibrated without the need for
human intervention.
design time also needs to be factored
into the cost of the converter. When using
a digital controller, the converter design
does not need to be done by a power
supply specialist. It can be done by the very
same digital hardware design engineer
developing the board. last-minute changes
can be quickly implemented because the
requirements are programmed into the
digital controller, something that can also
be done “on the fly.”
Performance
The kinds of applications addressed by
digital controllers are typically more
Advertisement
SPonSored By
involved than those for analog controllers.
Consider, for instance, a fast-occurring
20-a load step at an output voltage of 1 V.
at this low voltage, a 200-mV deviation
on the output (20%) may be unacceptable for many applications. resorting to
adding more output capacitance on the
board in order to minimize output voltage deviations unnecessarily burdens
the bill of materials cost while it also
slows down the converter’s response.
With a digital controller, implementing
advanced transient response algorithms,
such as ZmdI’s State-law Control,
reduces expenses while improving
transient response.
It is also important to know
that the lC filter on the output of a
dC/dC converter does not exhibit
real poles that can be compensated
for by the error amplifier’s compensation network. The poles are actually
complex, and their position depends
on the Q factor of the filter. an
unconditionally stable converter can
be designed with an analog controller,
but at the expense of performance that
can easily be obtained from a digital
controller. Just imagine having a converter with feedback and feed-forward
networks that adapt continuously to
your converter’s operating conditions.
This is what is achieved with digital
power control.
Converter size
The size of a digital converter will
typically differ from that of an analog
converter depending on the total number of external components needed in
order to address the features required by
the load.
as far as controller size is concerned,
it is important to know that process
geometries have become smaller in the
past years, allowing digital circuits to
benefit from this because they can be
scaled down in size much more readily
than their analog counterparts. as evidence of this, ZmdI’s high-performance
digital PWm controller, the ZSPm1000,
comes in a 4 x 4-mm Qfn package.
Small size also means less silicon area
and hence lower cost.
Efficiency
analog controllers can provide high
efficiency over a wide range of output
currents by switching between two modes
of operation. one is a constant or pseudo-
power delivered by a digitally controlled
converter and the digital controller’s active supply current. The digital controller’s operating current is generally higher
than its analog counterpart, but for the
Fig. 2: Comparison of the transient response of a digital controller (pink trace) vs. an
analog controller (white trace).
constant frequency mode for continuous
conduction of the inductor current, and
the other is a pulse-skipping mode for
light loads in which the inductor current
reaches zero within every switching cycle,
and the switching cycle is determined
by the droop time of the output capacitors. digital control does this too, but for
output voltages of approximately 1 V and
currents in the tens of amperes, additional considerations must be addressed
in order to minimize conduction losses
and save energy via the various standby
and sleep-mode techniques. once again, a
digital controller becomes the ideal choice
because it is able to be programmed in
various operating modes. In order to
reduce conduction losses, a driver moS
or drmoS power stage is also employed
to work alongside the digital controller,
for example the ZSPm9060 from ZmdI,
which can deliver an average current of up
to 60a. This part has been optimized to
provide a very high efficiency.
another aspect that tends to be
overlooked by power supply designers is
the relationship between the maximum
MAY 2013 • electronicproducts.com • ElEctronic Products
power levels it controls, this current
becomes an insignificant fraction of the
total power budget.
PoL modules
another application that also fits very
well for digital control is point-of-load
(Pol) modules. Producing dC/dC
converter modules requires a high degree
of automated production. Variations in
module outputs can be easily configured,
either via PmBus or via pin-strapping.
The module manufacturer can also tailor
the module’s characteristics in order to
further optimize it to the load.
Future trends in digital power
as the number of digital boards
continues to increase and the trend
toward more energy-efficient designs
continues to dominate, digital power will
continue to see a high growth potential
in the coming years. Cost savings can be
obtained through fast design turnaround
times, savings in staff personnel, savings
in production costs, and faster time to
market.
☐
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Interview with Thilo von Selchow,
President and CEO of ZMDI
May 14, 2013 in EEWeb Pulse (USA)
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July 25th, 2013 in Handelsblatt (Germany)
4 TITELTHEMA
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D
Der Soli ist eine
reine Abzocke der
Steuerzahler durch
eine Große Koalition
aus Union, Grünen,
SPD und der Linken.
Reiner Holznagel,
Präsident des Bundes der Steuerzahler
er Solidaritätszuschlag ist von
Mythen umgeben. Ein Mythos
lautet, die Ergänzungsabgabe
werde allein von den Westdeutschen gezahlt – obwohl auch
die Ostdeutschen finanzielle Solidarität mit
sich selbst zeigen müssen. Das führt zu einem weiteren Mythos: Der Soli wird als gelebte Solidarität des Westens mit dem Osten
dargestellt. Tatsächlich aber betonte die
Bundesregierung schon Anfang 1997, der
Begriff „Solidarität“ beziehe sich vor allem
auf die Ausgestaltung der Abgabe, die „ausnahmslos alle Steuerzahler – entsprechend
ihrer ökonomischen Leistungsfähigkeit –
belastet.
Um solchen Mythen die Grundlage zu
entziehen, empfiehlt der Konjunkturchef
des Wirtschaftsforschungsinstituts Halle,
Oliver Holtemöller: „Der Solidaritätszuschlag sollte in den Einkommensteuertarif
eingearbeitet werden, damit die Missverständnisse aufhören.“ Im nächsten Schritt
könne man sich dann darüber Gedanken
machen, ob die Höhe der steuerlichen Extrabelastung von 5,5 Prozent insgesamt angemessen sei. Für Steuersenkungen gebe
es aber nur Raum, wenn Ausgaben gekürzt
würden.
Auch der Chef des Zentrums für Europäische Wirtschaftsforschung (ZEW),
Clemens Fuest, sagte, wer den Soli abschaffen wolle, müsse eine „Gegenfinanzierung“ für den Bundeshaushalt
mitliefern. Fuest schlägt vor: „Der
Solidaritätszuschlag sollte
umbenannt werden in
Bundeseinkommenssteuerzuschlag.“ Denn das
Geld fließe nicht speziell
in die neuen Länder –
der Begriff sei „irreführend“.
Jenseits semantischer
Probleme verteidigte
CDU-Generalsekretär
Hermann Gröhe am
Montag trotz Kritik aus
den eigenen Reihen den
Vorstoß der Bundeskanzlerin. Er sehe „keinen Entlastungsspielraum in der
kommenden Legislaturperiode“, sagte Gröhe nach einer
Sitzung des CDU-Bundesvorstands. Die Frage einer Abschaffung
des Zuschlags stelle sich deshalb
nicht. Das Ziel, den Haushalt in Ordnung zu bringen, bedeute auch,
dass umfassende Steuersenkungen
– eine Abschaffung des Solis bedeutete eine jährliche Entlastung der
Steuerzahler von 13 bis 14 Milliarden
Euro – nicht auf der Tagesordnung
stehen könnten.
Merkel will den Solidaritätszuschlag beibehalten, aber die spezifi-
Helmut Kohl: Der damalige
Kanzler kündigte 1996 das Ende
des Solis an.
sche Förderung Ostdeutschlands nach 2019
beenden. Dann läuft der Solidarpakt II aus.
„Manche Regionen in den neuen Ländern
stehen wirtschaftlich besser da als Teile der
alten Bundesrepublik“, hatte die CDU-Vorsitzende am Wochenende gesagt.
Zur Begründung führte Merkel die Forderung von Thüringens Ministerpräsidentin Christine Lieberknecht (CDU) an, die zu
Recht darauf hingewiesen habe, dass nach
dem Ende des Solidarpakts II die spezifische Förderung für den Osten in eine Förderung nach regionaler Notwendigkeit umgewandelt werden könnte. Das heißt, dass
Merkel diesen Teil des Finanzausgleichs
zwar umwidmen, aber grundsätzlich beibehalten will.
Die SPD hat dagegen vor allem Spott für
die Regierungskoalition übrig. „Einmal
mehr wird mit viel Theaterdonner ein steuerpolitisches Fass aufgemacht“, kommentierte Fraktionsvize Joachim Poß die
schwarz-gelbe Debatte über die Abschaffung des Solidaritätszuschlags. Die Rollen
bei diesem „Uralt-Stück“ seien wohlbekannt: Die FDP versuche mit einer Soli-Diskussion im Sommerloch Anlauf für den
Sprung über die Fünfprozenthürde bei der
Bundestagswahl am 22. September zu nehmen.
Was Poß nicht erwähnte: SPD-Ministerpräsidenten scheuen sich nicht,
die Erhebung des Zuschlags über
das Jahr 2019 hinaus zu fordern. So
hatte NRW-Ministerpräsidentin
Hannelore Kraft schon in der vergangenen Woche deutlich
gemacht, dass sie es für
gerechtfertigt hält,
nach 2019 einen neuen Sonderfonds zu
beginnen. Die Strukturförderung sei jedoch auf das Prinzip
„Bedürftigkeit statt
Himmelsrichtung“
umzustellen. „Dies
wird auch im Rahmen der Verhandlungen für einen
neuen Länderfinanzausgleich eine Rolle spielen“,
sagte Kraft.
Hamburgs Erster
Bürgermeister Olaf Scholz
wirbt ebenfalls seit längerem dafür, den Solidaritätszuschlag als „Ergänzungsabgabe“ auch nach 2019 durch
den Bund zu erheben.
Ganz anders hingegen der
Präsident des Bundes der Steuerzahler, Reiner Holznagel.
Angesichts von Rekordsteuereinnahmen sei ein Festhalten
am Soli „reine Abzocke der
Steuerzahler durch eine Große Koalition aus Union, SPD,
Grünen und der Linken“.
Heike Anger, Michael Brackmann,
Dorit Heß, Jens Münchrath,
Thomas Sigmund
© Handelsblatt GmbH. Alle Rechte vorbehalten. Zum Erwerb weitergehender Rechte wenden Sie sich bitte an [email protected].
2013
2012
2011
200
2010
2009
2007
2006
150
2006
2005
2004
2003
100
2002
2001
2000
1999
1998
50
1997
1996
1995
1992
1991
0
Erzielte und erwartete Einnahmen
durch den Solidaritätszuschlag
Amtliche Daten des Bundesfinanzministeriums
AUFBAU OST
Siege und Ni
Auch im Osten gibt es
Erfolgsgeschichten –
doch die Abwanderung
der Bürger in den
Westen geht weiter.
Silke Kersting, Norbert Häring
Berlin, Frankfurt
D
ddp images
Forstetzung von Seite 1
2014
Handelsblatt | 1) gesetzlich festgeschrieben; 2) zwischen Bund und Ländern vereinbart | Quellen: Destatis, Bund der Steuerzahler, HB, Die Welt, BA, Arbeitskreis Volkswirtschaft Gesamtrechnung der Länder
300,8 Mrd. €
► Mit Ausnahme der FDP halten alle Parteien am Soli fest.
resden boomt. Der Mikrotechnologie-Cluster in der sächsischen Landeshauptstadt genießt Weltruf. Viele
High-Tech-Firmen haben sich angesiedelt.
Ebenso Jena: Die thüringische Stadt hat
nach der Wende auf optische Technologien
gesetzt und gilt heute mit Jenoptik und Carl
Zeiss Meditec als Vorzeigestandort.
In beiden Städten hat die Bundesregierung nach dem Mauerfall die in der DDR
entstandene Grundstruktur in der Mikround Optoelektronik gezielt gefördert. Am
Dresdener Stadtrand entstanden so hochsubventionierte Chipfabriken, die noch
STREIT ÜBER SOLIDARITÄTSZUSCHLAG 5
DIENSTAG, 23. JULI 2013, NR. 139
2
HERMANN OTTO SOLMS
Solidaritätszuschlag bis 2017
Wie der Bund am Soli verdient
2012
Aufkommen aus dem Solidaritätszuschlag 13,6 Mrd. €
An die neuen Bundesländer1
10,8 Mrd. €
davon Förderprogramme des Bundes2
3,5 Mrd. €
20
im Zeitraum 2005 bis 2019
„Der Vorstoß der
Kanzlerin ist ein
Vertrauensbruch“
2019
17,5 Mrd. €
3,1 Mrd. €
1,0 Mrd. €
207,8 Mrd. €
A
ls Vorsitzender der FDP-Bundestagfraktion hat Hermann Otto Solms den Soli
1995 wieder miteingeführt – heute streitet der Vizepräsident des Deutschen Bundestags für seine Abschaffung. Das Argument des
72-Jährigen: Die Abgabe war zur Finanzierung
der Einheit zeitlich befristet angelegt.
Schätzung
Aufkommen
15
105,4 Mrd. €
Zuweisungen
an die neuen
Bundesländer
Herr Solms, die Kanzlerin will den Solidaritätszuschlag über 2019 hinaus beibehalten.
Die Bürger haben erwartet, dass die Steuer
nicht endlos weiter erhoben wird. Muss man
da nicht von einer Soli-Lüge sprechen?
Solms: Der Vorstoß führt zu einem Vertrauensbruch gegenüber den Wählern. Die Bürger
haben fest damit gerechnet, dass der Soli in
einem überschaubaren Zeitraum entfällt. Das
wäre jetzt in weite Zukunft gerückt, sollte sich
die Union hier durchsetzen.
10
50,7 Mrd. €
Förderprogramme
in den neuen
Bundesländern
5
51,7 Mrd. €
0
2005
’06
’07
’08
’09
2010
’11
2012
’13
’14
2015
’16
’17
’18
2019
Werner Schuering/imagetrust
Differenz zugunsten des Bundes
Ost-West-Vergleich
Neue Bundesländer
Alte Bundesländer
35 000
Durchschnitt Deutschland
25 %
40 000
20 %
35 000
15 %
30 000
10 %
25 000
Hermann Otto Solms: „Die Grundlage für
den Soli gibt es nicht mehr.“
30 000
Was stört Sie am Soli konkret?
Als Schwarz-Gelb unter Helmut Kohl den Zuschlag 1995 wieder einführte, war ich Fraktionschef der FDP im Bundestag. Wir waren
uns damals einig: Der Soli sollte zur Finanzierung der Einheit dienen. Nachdem dieser
Zweck 2019 ausläuft, ist die Grundlage für den
Soli entfallen. Jetzt müssen die Bürger hören,
dass das alles Makulatur sei. Die Union will
das Geld für andere Zwecke einsetzen.
25 000
20 000
15 000
10 000
Durchschnittliches
Bruttoinlandsprodukt
pro Kopf und Jahr in Euro
5 000
5%
0
20 000
Arbeitslosenquote
in Prozent
0%
1991
1995
2000
2005
2012
1991
1995
2000
2005
2012
15 000
1991
Durchschnittliches
Arbeitnehmerentgelt
pro Jahr in Euro
1995
2000
2005
2012
ederlagen
heute wichtige Standbeine der sächsischen
Wirtschaft sind. Auch Unternehmen mit
Wurzeln in der DDR haben sich behauptet.
Zum Beispiel das Zentrum für Mikroelektronik Dresden (ZMDI). Es wurde vor mehr
als 50 Jahren gegründet und galt lange als
Herzstück der Mikroelektronikforschung
der DDR. ZMDI ist heute weltweit aktiv und
auf den Bau von Mikrochips konzentriert,
die Autos oder Beleuchtungsanlagen energieeffizienter machen.
Es gibt sie, die Positivbeispiele in den
neuen Ländern. Einerseits Unternehmen
aus der früheren DDR, Rotkäppchen etwa,
eine ostdeutsche Sektmarke, die heute
auch gern im Westen gekauft wird. Andererseits umsatzstarke Unternehmen wie
der Berliner Energieanbieter Vattenfall, eine Tochter des schwedischen VattenfallKonzerns. Doch genau da liegt das Problem: In den neuen Bundesländern sind
in der Mehrzahl Tochtergesellschaften internationaler oder westdeutscher Konzerne vertreten. Große Firmenzentralen gibt
es so gut wie nicht im Osten Deutschlands.
Ausnahmen sind die Deutsche Bahn oder
die Dienstleistungsgruppe Dussmann, die
ihren Sitz in Berlin haben.
Die Erfolgsgeschichten kommen häufig
von Unternehmen mittlerer Größe, etwa
Biotronik oder Eckert & Ziegler. Davon
profitiert auch der Arbeitsmarkt. Die Arbeitslosigkeit in den neuen Ländern ist
derzeit so niedrig wie seit 1991 nicht
mehr. Mit knapp 9,9 Prozent beträgt sie
allerdings immer noch das 1,7-Fache des
Westniveaus. So groß war der Abstand
auch von 1994 bis 1997. Bei stagnierender
Konjunktur war er allerdings auch schon
merklich größer. Hinzu kommt, dass der
Wegzug von Arbeitnehmern die Arbeitslosenquote in den neuen Bundesländern
gedrückt hat, was zeigt, dass sich die Lebensbedingungen nicht angeglichen ha-
18,7 %
der sozialversicherungspflichtigen Stellen in
Deutschland liegen in
den neuen Ländern.
ben. In den vergangenen zehn Jahren haben die neuen Länder sieben Prozent ihrer Bevölkerung verloren, im Westen
betrug der Rückgang nur 1,5 Prozent.
Auch beim Blick auf die Beschäftigungsentwicklung gibt es wenig zu feiern. Mitte 1992 stellten die neuen Länder noch
knapp 23 Prozent der gesamtdeutschen
sozialversicherungspflichtigen Arbeitsplätze. Ende 2012 lag der Anteil mit 18,7
Prozent allerdings so tief wie noch nie
seit der Wiedervereinigung.
Einzig beim Lohnniveau sind der Osten
und der Westen einander näher gekommen. Von 57 Prozent des Westniveaus 1991
stieg das durchschnittliche Lohnniveau im
Osten auf 82 Prozent 2012. Seit dem Jahr
2009 hat sich diese Entwicklung jedoch
nicht weiter fortgesetzt. Insgesamt spiegelt das auch die Angleichung der Wirtschaftskraft wider – jedenfalls, wenn man
sie auf die im Osten deutlich schneller sinkende Bevölkerung bezieht. Von 43 Prozent des Westniveaus stieg die relative
Wirtschaftsleistung pro Einwohner bis
2009 auf 72 Prozent. 2012 lag sie mit 71
Prozent des Westniveaus aber wieder etwas niedriger.
Die Kanzlerin will das Geld in Infrastrukturprojekte stecken. Was haben Sie dagegen ?
Ich bestreite doch nicht den Finanzierungsbedarf von maroden Brücken oder Straßen.
Doch dieser Vorstoß passt zur gegenwärtigen
Steuerdiskussion. SPD und Grüne wollen den
Menschen über höhere und neue Steuern an
den Geldbeutel. Die Union hat ein Füllhorn
von Wahlgeschenken ausgebreitet, für den sie
den Soli zweckentfremden will. Ich bin aber
jetzt schon ein paar Jahre im Bundestag und
weiß, was mit solchen Mitteln gerne passiert.
Was denn ?
Die mittelständischen Unternehmen investieren weit mehr als 50 Prozent ihrer Erträge.
Der Investitionsanteil an den Staatsausgaben
beträgt nur neun Prozent. Wenn die Einnahmen der Wirtschaft durch Steuern gekürzt
werden, führt dies auch zu einer Reduzierung
der Investitionen. Damit verspielt man die Zukunft. Allein die Wahlversprechen der Union
bewegen sich im zweistelligen Milliardenbereich. Wenn es jetzt heißt, man wolle die Mittel des Soli nach 2019 gesamtdeutsch zweckmäßig einsetzen, habe ich meine Zweifel.
Sie glauben nicht, dass das Geld für Investitionen in die Infrastruktur ausgegeben wird?
Gestern kamen aktuelle Zahlen zu den Steuereinnahmen im ersten Halbjahr 2013. Der Staat
schwimmt im Geld, doch er kommt nie damit
aus. Die Koalition hat sich nun dazu durchgerungen, einen strukturell ausgeglichen Haushalt für das Jahr 2014 vorzulegen. Wir wollen
das eben nicht wie die Union über höhere Steuern oder die Fortsetzung von finanziellen Belastungen erreichen. Die FDP will den Haushalt
konsolidieren, ohne die Steuern zu erhöhen.
Die Fragen stellte Thomas Sigmund.
Sensor signal-conditioning ICs ease the design of sensor systems
by David Grice (ZMDI)
October 1st, 2013 in Electronic Industry (USA)
sponsored by
Sensor signal-conditioning ICs
ease the design of sensor systems
Cost effective and power efficient, sensor-signal-conditioning ICs deliver
high precision and accuracy if implemented properly
BY DAVID GRICE
Field Application Engineer,
ZMDI, www.zmdi.com
T
he market for sensors and
sensor-related components is a
high-growth industry expected to
expand in automotive, industrial, medical, and consumer applications. Products
such as media players, tablet PCs, and
smartphones are driving significant
growth in the sensor market, requiring a related increase in the number of
designers and manufacturers integrating
sensors into modules for resale or for
their own products. The wide range of
sensing element types and demands for
faster time to market and lower costs
present numerous challenges, even for
veterans of sensor design. The perennial challenge for sensor
interface designers is correcting and
calibrating the inherent non-idealities
present in transducers, typically offset
and nonlinear response to stimulus with
a temperature dependence for one or
both of these factors. There are a host of
custom design approaches and solutions
to this problem, but the availability of
commodity integrated circuits offers
designers new choices that are powerful
and cost-effective. By combining precise,
programmable analog circuitry with
high-density digital controllers dedicated to processing correction algorithms,
these sensor-signal-conditioner (SSC)
ICs reduce the design time and cost
of sensor systems while providing the
designer with a menu of built-in capabilities and support tools for implementing sensor correction. Understanding
the sensor’s characteristics and how to
configure its corresponding SSC are key
ingredients for obtaining optimum performance and keeping costs low.
Overview of sensor correction
Transducers exhibit various types and
degrees of offset and nonlinear response.
The basic idea of calibration and correction is to maximize the usable range and
transform the nonlinear response into a
predictable linear output that minimizes
the error in the sensor output. The nature
while the span decreases with increasing
temperature. The challenge is to understand what the exact nature of the dependence is and remove its contribution to
system error. Plotting the offset and gain
versus temperature will reveal another set
of curves with linear, quadratic, or higher-order dependence on temperature.
Fig. 1: Typical sensor responses to input
stimulus.
Fig. 2: Sensor output variation over
temperature.
of non-idealities varies widely between
sensor types, and the difficulty and complexity of applying corrections increase
in proportion to the magnitude and
degree of these undesirable effects.
Figure 1 illustrates several types of
sensor responses. Each has different basic
characteristics and related correction
issues. S1 has low offset and relatively low
nonlinearity. S2 has a narrow span but a
very high offset, which must be removed
before applying sufficient gain to create a
useful signal level. S3 has a sharp “knee,”
and piecewise linear correction is generally
a good option for these types of nonlinearities. S4 has an inflection point and would
require at least a third-order polynomial
correction to achieve a high accuracy over
the entire measurement range.
Another important factor to consider
is how these sensors behave over temperature. Figure 2 shows a typical scenario
for the temperature variation of a sensor
element. In this case, the offset increases
OCTOBER 2013 • electronicproducts.com • ElECTROniC PROduCTs
Each individual sensor element will
have its own characteristic span and offset
with respective temperature dependencies. The type of correction algorithm
applied must also account for the type
and degree of these differences across
variations such as process tolerances,
shifts between manufacturing lots, or
package stress effects introduced in the
next assembly level.
Hardware implementation
The block diagram shown in Fig. 3
presents a practical and cost-effective
approach to sensor calibration and
correction. It is a 16-bit resolution resistive-bridge sensor signal conditioner with
built-in correction algorithms capable
of compensating for a variety of undesirable sensor characteristics. A proprietary microcontroller with 18-bit digital
signal processing (DSP) performs the
necessary calculations for the correction
algorithms using calibration coefficients
Advertisement
sponsored by
Table 1: List of correction algorithms for an SSC showing the number of
calibration points and the correction factors applied.
Fig. 3: Block diagram of a sensor signal conditioner IC.
stored in nonvolatile memory. In addition,
this device performs auxiliary operations
including temperature sensing and bridge
biasing, and it has multiple communication
interfaces. It represents a complete solution
for interfacing and correcting the output of
a sensor bridge, providing a precise, accurate, and compensated sensor output.
Getting to know your sensor
One of the most important and effective
tasks that the designer can carry out is a
thorough characterization of the sensor
element. Time and effort invested in this
important step will pay off in the long
run by reducing overall design time and
development costs, improving the overall
system performance and robustness, and
ultimately reducing production test time
and cost. It is tempting to rush through
this part of the product development
cycle, but experienced sensor system
designers will testify to the importance of
spending the necessary time and resources to characterize and analyze sensor
data before proceeding to the next step of
developing an optimized sensor correction algorithm.
For example, consider the response
curve of sensor S3 in Fig. 1. If the input
range is limited to between 10% and 30%
or 60% and 90%, a first-order gain and
offset correction algorithm might suffice,
depending on temperature variations.
However, if the sensor must operate
across the entire sensor input range, a
more sophisticated correction algorithm
is needed. Even if the intended range of
operation appears to be confined to one
of the linear regions, consider what would
happen if a future lot of sensors were to
shift so that the knee of the curve moved
into what was previously a linear region?
Not having the flexibility and availability
of more sophisticated correction techniques could require significant redesign.
It is vitally important for the sensor system designer to understand the
characteristics of the sensor across the
input measurement range and over the
operating temperature range.
Some of the more important considerations includethe more important
considerations include • The shape and order of the sensor response over the desired measurement range,
including at least a 10% margin outside the
expected minimum and maximum values.
• The type and order of temperature
dependence for offset and span.
• The consistency of the measured parameters. Consider what would be the effect on
the correction algorithm if future manufacturing lots have a shift in a significant feature
such as an inflection point or the sign of a
temperature coefficient.
• Whether the characterization data set is adequate and
statistically significant. This
includes the number of devices
tested and the number of points
measured for each.
• How much error the data
acquisition system contributes
to the characterization.
• Selecting and implementing
the best correction technique
production. With the sensor characterization data in hand, the degree and type
of correction required for gain and offset
can be matched with the best algorithm
available in the SSC.
Table 1 is a list of the some typical
algorithms available in commercial ICs.
The algorithms are organized by the type
and degree of correction, and the second
column indicates how many measurement points are needed to calculate the
calibration coefficients for each algorithm.
The next columns list the element of correction each calibration method applies
and describe the sensor characteristics
that must be isolated and quantified to determine the optimal algorithm. TC refers
to the temperature coefficient. Eliminate
algorithms that correct for negligible
effects in the particular system and choose
the one with the least number of measurement points.
Once the sensors have
been characterized and the
dataset is evaluated, the next
Fig. 4: Screen capture of software aid for selecting and
step is to narrow the field
evaluating calibration methods.
of correction options. The
SSC manufacturers usually provide
ultimate goal is to produce measurement
hardware and software for their devices
results that meet sensor product accuracy
that allow selecting and evaluating the calrequirements with the minimum number
ibration methods quickly and easily. Softof points necessary for calibration during
OCTOBER 2013 • electronicproducts.com • ElECTROniC PROduCTs
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Neueste Forschung macht‘s möglich: Schnelle
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Forschungsprojekt
by ZMDI, Infineon, Continental, Audi
August 5th, 2013 on www.infineon.com
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Home> Über Infineon> Presse
Neueste Forschung macht’s möglich: Schnelle
Fehlerbehebung im Fahrzeug durch DIANAForschungsprojekt
Presseinformation der Projektpartner des deutschen Forschungsprojekts
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5. August 2013
Neubiberg, 5. August 2013 – Ab 2015 könnten sich die Werkstattaufenthalte für Fahrzeuge beträchtlich verkürzen.
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Infineon Verfahren entstanden, mit denen eine differenzierte Fehlererkennung und damit die schnellere
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Die Fahrzeugelektronik ist heute überaus komplex. Durchschnittlich 80 elektronische Steuergeräte gibt es im Auto; im
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Qualitätskontrolle aus der Produktion der Halbleiterindustrie. Diese Verfahren wurden von den DIANAForschungspartnern so weiterentwickelt, dass die im Fahrzeug verbauten Chips unmittelbar für die Eigendiagnose des
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Bewähren sich die Diagnosetechniken im Fahrzeug, bieten sich weitere sicherheitsrelevante Anwendungsfelder an,
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Das Projekt DIANA wurde vom Bundesministerium für Bildung und Forschung (BMBF) im Rahmen der HightechStrategie der Bundesregierung und des Programms "Informations- und Kommunikationstechnologie 2020" (IKT 2020)
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Weitere Projektbeteiligte
Unterstützt wurden die vier Projektpartner von dem Fraunhofer-Institut für Integrierte Schaltungen Dresden, der
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Die AUDI AG hat als Automobilhersteller im Premiumsegment im Jahr 2012 weltweit 1.455.123 Automobile an Kunden
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http://www.infineon.com/cms/de/corporate/press/news/releases/2013/INFXX201308-... 15.10.2013
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Über Continental
Continental gehört mit einem Umsatz von 32,7 Milliarden Euro im Jahr 2012 weltweit zu den führenden
Automobilzulieferern. Als Anbieter von Bremssystemen, Systemen und Komponenten für Antriebe und Fahrwerk,
Instrumentierung, Infotainment-Lösungen, Fahrzeugelektronik, Reifen und technischen Elastomerprodukten trägt
Continental zu mehr Fahrsicherheit und zum globalen Klimaschutz bei. Continental ist darüber hinaus ein kompetenter
Partner in der vernetzten, automobilen Kommunikation. Continental beschäftigt derzeit rund 173.000 Mitarbeiter in 46
Ländern. Weitere Informationen unter www.continental-corporation.com.
Über ZMDI
Die Zentrum Mikroelektronik Dresden AG (ZMDI) ist ein weltweiter Anbieter von Analog- und Mixed-SignalHalbleiterlösungen für Automobil-, Industrie-, Medizin-, Mobile Sensing-, IT- und Verbraucheranwendungen. Diese
Lösungen ermöglichen unseren Kunden, Produkte im Bereich Power Management, Beleuchtung und Sensoren zu
entwickeln, die für ein Höchstmaß an Energieeffizienz sorgen. Seit mehr als 50 Jahren befindet sich der Hauptsitz von
ZMDI in Dresden. Mit mehr als 350 MitarbeiterInnen weltweit betreut ZMDI seine Kunden mit Verkaufsstellen und
Entwicklungscentern in Deutschland, Italien, Bulgarien, Frankreich, Irland, Japan, Korea, Taiwan und den Vereinigten
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Unter der Haut
by Dr. Marko Mailand (ZMDI)
October 2013 in electronik JOURNAL (Germany)
Aktive Bauelemente
ASIC
Unter der Haut
NFC- und Sensor-Komponenten auf einem Chip zur In-Vivo-Blutanalyse
Spezifische Kommunikations- und Sensortechnologien mit modernsten biochemischen Lösungen kombiniert: Mit
diesem Halbleiter adressiert ZMDI die kontinuierliche telemedizinische Überwachung von Blutparametern. So
sollen zum Beispiel Diabetes-Patienten mehr über ihren Blutzuckerspiegel erfahren, ohne sich Blut zu entnehmen.
Autor: Dr. Marko Mailand
M
it mehreren Millionen registrierten Erkrankungen ist
Diabetes heute eine Volkskrankheit und eine der wesentlichen Ursachen für zahlreiche Kreislauferkrankungen. Medizinisch unterscheidet man zwischen Patienten, bei denen die Bauspeicheldrüse kein Insulin produziert
(Diabetes Typ-1) und Betroffenen, bei denen der Körper eine Resistenz gegen Insulin zeigt (Diabetes Typ-2). Insbesondere die Typ1-Diabetes erfordert eine möglichst kontinuierliche Überwachung
des Blutzuckerspiegels.
Bild 1: Der Fluoreszenz-Sensor von
Senseonics misst nur 15 mm x 3 mm;
er dient als Basis für ein implantierbares Glukosemesssystem.
Bild: fotolia: Kurhan
28
Zur Lösung dieses Problems hat das Unternehmen Senseonics
einen Fluoreszenz-Sensor entwickelt, der die Basis für ein implantierbares, kontinuierliches Glukosemesssystem bildet. Das neuartige Sensor-Systemkonzept ist neben der kontinuierlichen Glukosemessung auch auf eine ganze Reihe weiterer Anwendungen adaptierbar. Die Elektronik des ambulant implantierbaren (in-vivo)
Sensor-Moduls (Bild 1) ist in einem speziell für Senseonics entwickelten ASIC von ZMDI integriert. Das elektronische Systemkonzept basiert auf der Nutzung ISO-kompatibler Nahfeld-Kommuni-
elektronikJOURNAL 05/2013
www.elektronikjournal.com
Aktive Bauelemente
ASIC
Bilder: ZMDI
Bild 2: Das Prinzipbild der
Funktionsweise des In-Vivo-Glukose-Biosensors zeigt, dass der
Sensor per NFC mit Mobilgeräten
kommuniziert.
Bild 3: Sensor-System-Topologie:
Der aktive Reader (links, NFCMaster) versorgt und kontrolliert
den passiven NFC-Sensor-Transponder.
kation (NFC) und -Energieversorgung (ISO15693, zukünftig auch
ISO14443-3) mittels loser, induktiver Kopplung. Befehle (zum Beispiel Messen, Daten speichern, Daten lesen, Diagnose), Daten und
Energie werden dabei drahtlos vom NFC-Master zum implantierten Sensor-Modul, dem NFC-Sensor-Transponder, übertragen
(Bild 2). Letzterer steuert den Ablauf, führt die jeweiligen Messaufgaben durch und sendet die Daten zurück an den NFC-Master,
welcher die einzelnen Messwerte zum Beispiel in einen Glukosewert umrechnet. Der NFC-Master kann beispielsweise als ein spezifisches Armbandgerät ausgeführt oder auch direkt in einem
Smartphone integriert sein.
Durch die Kombination von Wireless-NFC-Technologie mit einem optischen Signalübertragungsweg für die Bestimmung der
Blutparameter – speziell der Glukosekonzentration – wird aufbautechnisch eine komplette Verkapselung des implantierbaren NFCSensor-Transponders möglich. Da nun aber auch die Energieversorgung drahtlos geschieht und das Sensor-Modul folglich batterielos agiert, ist die Lebensdauer nur noch durch inhärente Sensoreigenschaften begrenzt – das ist im Wesentlichen das Nachlassen
der Fluoreszenzintensität des biochemischen Indikators, der sich
auf der Außenseite des Sensors befindet.
NFC/RFID-Kompatibilität
Wesentliche Anwendungsvorteile für die Patienten resultieren aus
der Integration von ISO-standardkompatiblen Kommunikationsund Power-Management-Komponenten. Die aktuelle ASIC-Version implementiert ein ISO15693-Transponderinterface. Das analoge ISO-Frontend nutzt einfache Amplitudendetektion zur Demodulation und ein steuerbares Lastverhalten mittels einer ClampSchaltung zur passiven Rückmodulation. Bei Letzterem wird das
Magnetfeld mit der Modulationsfrequenz von ungefähr 423,75
kHz entsprechend gedämpft; diese Dämpfung detektiert dann der
Reader oder NFC-Master. Der Anwendungsvorteil der ASIC-Realisierung als passiver Transponder liegt auf der Hand: im SensorModul wird keine Batterie benötigt, und es besteht damit keine
Einschränkung der Lebenszeit und In-Vivo-Verbleibedauer aufgrund von Energieversorgungseigenschaften.
Störungen vermeiden
Die besondere Herausforderung besteht nun darin, zu verhindern,
dass der Reader jedes Last-Schaltverhalten der digitalen und analogen Baugruppen, insbesondere des Sensor-Teils, als Rückmodulation fehlinterpretiert (Bild 3). Zusätzlich muss gewährleistet sein,
dass für eine Sensor-Messung oder einen Messzyklus ausreichend
Energie zur Verfügung steht.
Die größten Stromverbraucher des ASICs sind der Analog-Digital-Wandler sowie der LED-Treiber beziehungsweise die LED an
sich. Diese brauchen etwa 0,35 mA bei einer intern geregelten
Spannung von 2,8 V (ADC) oder bis zu 2 mA bei der ungeregelten
Betriebsspannung Vsup ~ 4 V (LED) entsprechend der Topologie in
Bild 3. Um trotz dieser notwendigen Lastunterschiede keine unerwünschten Frequenzanteile in der Luftschnittstelle zu generieren
Auf einen Blick
Alles drin
Ein besonderer ASIC von ZMDI nutzt NFC zur Kommunikation und
Energieversorgung, kombiniert mit dem Treiber für eine UV-LED und
den entsprechenden Photo-Sensoren sowie der Signalaufbereitung
und -Verarbeitung. Mit diesem Chip hat Senseonics eine implantierbare Lösung zum Messen von Blutparametern entwickelt.
infoDIREKT www.all-electronics.de
505ejl0513
29
Aktive Bauelemente
ASIC
Tabelle: Optionen und Eigenschaften
des Multi-Sensor-Front-Ends
Mess-/Sensor-Typ
Messbereich
Maximale
Empfindlichkeit
Fotodioden-Strom
1,16 µA
4,5 pA/count
Temperatur
+15 … +50 °C
18 mK/count
Externe Spannung
-1,5 … +1,5 V
1,2 mV/count
Feldstärke (Iclamp)
140 mW
10 µW/count
Spannung: LED-Treiber
1,6 V
1 mV/count
Diagnose – Optik
1,16 µA
4,5 pA/count
Diagnose – Temperatur
+15 … +50 °C
18 mK/count
Im ASIC ermitteln eine ganze Reihe an Sensoren wichtige Daten
über den Patienten. Quelle: ZMDI.
Bild 4: Die Systemsteuerung und der Messablauf ermöglichen bis zu acht
Messungen pro Zyklus.
sind im ASIC speziell geformte, stetige Ein/Ausschalt-Rampen in
der Power-Management-Einheit integriert. Dadurch werden die
Spektralanteile, verursacht durch das Schalten, in einen Bereich
um die 400 kHz verschoben – das relevante Passband liegt aber bei
13,56 MHz ±1 MHz. Das Datensignal wird somit nicht gestört.
als ausreichend ist. Das ermöglicht eine Situations-optimale, energieeffiziente Systemauslegung der gesamten Applikation (NFC/
Sensor-Transponder in Zusammenspiel mit NFC-Master). Die Tabelle zeigt die entsprechenden Dynamikbereiche und Empfindlichkeiten der integrierten Sensoren.
On-Chip-Sensorik
Adaptierbarkeit durch digitale Steuerung
Das Hauptmessprinzip zur Ermittlung der Glukosekonzentration
nutzt zwei optische Kanäle. Eine vom ASIC gespeiste UV-LED
emittiert Licht, welches von der Kapseloberfläche zurückgeworfen
wird. Ein Spektralanteil besteht dabei genau aus dem emittieren
UV-Licht und beinhaltet keinerlei Nutzinformation.
Der Hauptspektralanteil jedoch, resultiert aus der Fluoreszenz
der Indikatorchemikalie an der Außenseite des Sensormoduls.
Hierbei werden genau nur jene Indikatoren zur Fluoreszenz angeregt, an welche sich Glukosemolekühle gekoppelt haben (Bild 2).
Dabei gilt, dass die Intensität der Fluoreszenz direkt von der Konzentration der Glukose abhängt. Beide Spektralanteile (UV-Reflektion und Signal-Fluoreszenz) werden von spektral selektiven OnChip-Fotodioden detektiert und im ASIC analog aufbereitet und
digitalisiert.
Alle biochemischen Prozesse sind temperaturabhängig. Zur
Kompensation dieses Einflusses ist im ASIC ein hochgenauer Temperatursensor integriert. Über diesen kann auf weniger als 0,2 K
genau die tatsächliche Temperatur des Sensor-Moduls und des
umgebenden Gewebes bestimmt werden.
Die digitale Steuerung der einzelnen Sensorkanäle erlaubt bis zu
acht unterschiedliche Messungen pro Messzyklus. Ein Messzyklus
ist dabei die tatsächliche Reaktion des NFC/Sensor-Transponders
auf einen einzelnen Messbefehl des NFC-Masters. Je nach den gewünschten Informationen sowie der dafür notwendigen Messabfolge werden in einem Zyklus Messungen mit und ohne emittierender LED durchgeführt (Bild 4), die Einzelwerte in On-ChipRegistern zwischengespeichert und nach Beendigung aller Messungen die gesammelten Ergebnisse über die NFC-Schnittstelle
übermittelt. Die einzige Begrenzung liegt dabei darin, dass der
NFC-Master entsprechend der ISO-Standards eine Antwortzeit
von maximal 20 ms zulässt. Ein Messzyklus inklusive Setup und
Antwort muss somit innerhalb dieser Zeit geschehen, um kein NoResponse-Timeout-Ereignis auszulösen.
Die Auswertung und Interpretation der einzelnen Sensor-Messwerte geschieht dann softwarebasiert auf der NFC-Master-Seite.
Die freie Konfigurierbarkeit des Messzyklus’ ermöglicht die Anwendung des ASICs und seiner Einzelsensoren in verschiedenen
Applikationen. So sind neben der Glukosemessung beispielsweise
auch Messungen für Blutsauerstoff, Blutalkohol und vieles mehr
denkbar. Hierfür kann das elektronische Sensor-System einfach
angepasst werden – es bedarf dafür aber anderer biochemischer
Indikatoren.
Selbstdiagnose
Darüber hinaus sind im ASIC mehrere Eigendiagnostik- und Applikations-Status-Sensoren integriert. Bei der Eigendiagnostik
werden dem Temperaturmesspfad oder dem optischen Messpfad
(über die Fotodioden) vordefinierte Schaltungsoffsets hinzugefügt,
die zu einer bekannten, erwarteten Änderung des Analog/DigitalWandler-Ergebnisses im Verhältnis zur entsprechenden Nicht-Diagnostik-Messung führen müssen. Dadurch lassen sich eventuelle
ASIC-interne Alterungs- oder Drift-Effekte auch im implantierten
Zustand des Sensors erkennen.
Der On-Chip-Statussensor zur Messung der aktuell verfügbaren
Feldstärke ermöglicht es, dem Patienten mitzuteilen, ob die Kopplung, sprich die Lage des NFC-Masters relativ zum Sensor-Modul,
ausreicht oder verbessert werden muss, um genügend Energie für
den Betrieb zu übertragen. Auf diesem Weg kann der Sonsor den
NFC-Master auch informieren, wenn die Übertragungs- oder Sendeenergie sinken darf – falls die induktive Kopplung gerade mehr
30
Im Test
Derzeit befindet sich das erste Gesamtsystem von Senseonics zur
Glukosemessung in der klinischen Erprobung in den USA, Kanada, Großbritannien, Deutschland und Indien. Die Entwicklung
dieses Systems und des zugrunde liegenden NFC/Sensor-Transponder-ASICs von ZMDI ist dabei ein erster Schritt auf dem Weg
zu vollständig autonomen, robusten telemedizinischen und klinischen Anwendungen, die sich vollständig in den normalen Alltag
integrieren lassen. (lei)
n
Der Autor: Dr. Marko Mailand ist Projekt Manager für MixedSignal-IC-Entwicklung im Bereich Medical, Consumer und
Industrial bei ZMDI in Dresden.
Designing an ASIC Chip to Control an Implantable
Glucose Measurement Device
by Uwe Günther (ZMDI); Andrew DeHennis (Senseonics, Inc.)
November 2013 in Medical Design Briefs (U.S.)
Sensor module design improves automotive
electrical integration
by Torsten Herz (ZMDI)
2014 in 21ic. eBooks (online publication) in Asia
传感器模块设计促进汽车电子的集成
作者：ZMDI 公司，Torsten Herz
得益于最新的基础传感器的控制系统所提供的精确、实时的监测，新汽车引擎的工作效率更高，对环境的影响更小。
这种性能改善的一项结果是，车辆中传感器应用的数量在过去几年中突破了两位数的增长。另一项结果是，在车辆中增加
更多的传感器模块成为一项趋势。这些模块必须可靠、强韧，必须能够在恶劣的物理、化学和电气压力条件下长期稳定工
作，并具有高精度。
此外，汽车传感器模块还需要一系列内置的诊断功能，以支持汽车 OEM 厂商“按需维护”的政策，以及安全攸关的
传感器应用（比如刹车压力传感）所需的特殊故障模式操作。
对于传感器模块而言，耐化学性（即对介质、湿气和腐蚀的免疫性）和物理强韧性（例如耐冲击和振动）主要取决于
所采用的材料以及组装和连接技术。电气强韧性，即电磁兼容性（EMC），取决于应用电路、电子元器件（集成电路，分
立器件）以及应用电路中的电气连接的布局走线。
本文将描述汽车传感器模块于电气强韧性方面的设计与应用。采用 ZSC31150 传感器信号调理器（SSC 集成电路）能
够设计出高精确度的传感器模块，其不仅能够在-40 至+150°C 的温度条件下工作，而且能够提供更好的 EMC 性能以及一系
列保护和诊断功能，以用于处理 SIL2/ASIL-B 等级的关乎安全的应用。采用传感器模块的智能化电气设计，将所有 EMC
相关参数考虑在内（即，寄生电容和电感），可以在最优的模块成本下实现高度的电气强韧性和内置的诊断功能，以及对
被测信号的极高精度测量。
因为传感器系统和处理单元之间的机械设计和互连对其电磁行为有着重要的影响，所以针对嵌入式传感功能（ESF）
和独立传感器模块（SASEM）使用不同的方法是至关重要的。
就 ESF 而言，传感器电子的位置靠近处理单元——在汽车应用中就是电子控制单元（ECU）。ESF 和 ECU 之间的连
接通常非常短（<<30cm），一般以印制电路板（PCB）上的走线来实现。现代 ESF 都提供了数字接口，例如串行外设接口
（SPITM，微芯科技的商标），其连接到 ECU 的微控制器。因为在同一 PCB 上且距离较近，因此有几种选择可供满足汽车
中严格的 EMC 要求（即，屏蔽或使用外部保护器件）。ESF 的一个例子就是气压传感。
对 SASEM 而言，配置是完全不同的。它们往往通过最长可达 2.5 米的无屏蔽线束连接到 ECU（参见图 1 中的示
例）。模块外壳（金属或塑料材质）内部可用的电路板空间是非常有限的，并趋于进一步的微型化，因为更少的材料耗费
等同于更轻的重量，进而等同于更低的成本。取决于不同的供电方式（电池供电或 ECU 供电），有各种兼容的输出接口：
电池供电的 SASEM
•
•
•
•
•
脉宽调制（PWM）输出（高边负载）
PWM 输出（低边负载）
控制器区域网络（CAN 总线）接口
本地互联网络（LIN 总线）接口
纯粹的模拟电压输出
ECU 供电的 SASEM
•
•
•
比值测量模拟电压输出
SAE J2716 单边半字节传输（SENT）接口（快速、单向的点到点数字数据传输）
外设传感器（PSI5）接口（两线电流编码的数字数据传输）
图 1：汽车压力传感器模块的典型构造
ECU
V+
OUT
VHarness(1=1.7m)
Plug for Electrical Connection
Case of the Module
Electronic Parts
PCB
Plug for Pneumatic or Hydraulic Connection
Pressure Supply Adaptor(“PSA“) with Sensor
System to be Monitored
ECU
V+
OUT
V线束（I=1.7 米）
电气连接插头
模块外壳
电子器件
印制电路板（PCB）
气动或液压连接插头
带传感器的压力适配器（PSA）
待监测系统
对客车而言，使用 ECU 供电的 SASEM 来提供比值测量模拟电压输出这种方式仍然很常见。常见的供电电压大约是直
流 5V±10%，而单个 SASEM 总的电流消耗应当≤10mA。如前所述，外壳的工作条件相当恶劣，这就导致了一些有效的无
源 EMC 保护器件无法使用，比如铁氧体磁珠，它只能工作在最高+125°C 的温度下。
SASEM 的 EMC 要求
取决于模块的不同设计（例如，模块外壳的材料），ZSC31150 的差分输入端 VBP 和 VBN 到 VSSA 之间可能额外需要
两个 10nF（最大）电容（如图 2 绿色部分所示），以满足 SASEM 的 EMC 规范——这就需要我们对有关典型的汽车 EMC
要求加以讨论。
图 2：ZSC31150 汽车应用电路
5VDC
Standardized Artificial Network(AN)
1μF
1μh
100nF
Application-Specific Test Network
VDD
VOUT
VSS
DC
BCI Antenna at Varying Positions
Harness(1=1.7m)
Case of the Module
RF
GND=chassis
IRF_sink
IRF_source
ZC_GND
PCB
CS_PSA
SSC-IC+ext.caps
PSA
CV+_C
CVOUT_C
CV-_C
ZPSA_C
直流 5V
标准化人工网络（AN）
1μF
1μh
100nF
专用测试网络
VDD
VOUT
VSS
直流
各种位置处的 BCI 天线
线束（I=1.7 米）
模块外壳
射频
地=机壳
IRF_sink
IRF_source
ZC_GND
PCB
CS_PSA
SSC 集成电路+外部电容
PSA
CV+_C
CVOUT_C
CV-_C
ZPSA_C
重要注解：强烈推荐在设计模块之前为每种 EMC 测试定制该电路，因为不同的 EMC 测试电路可能会要求不同的模块
设计。“通用的”解决方案往往过于昂贵。
为了满足苛刻的汽车 EMC 要求，必须考虑所有的相关电气寄生参数，特别是电气传感器电路和 SASEM 的其他传导器
件之间的寄生电容，如图 3 所示。模块的结构可能有许多不同的配置，其在汽车内部的组装如表 1 所示。外壳和压力适配
器（PSA）都可以是塑料或金属的，并且二者都可以与底盘有电流接触或没有接触。
模块构造
塑料外壳和塑料 PSA
塑料外壳和金属 PSA
金属外壳和塑料 PSA
金属外壳和金属 PSA
金属外壳和金属 PSA
汽车装配
与汽车底盘没有电流接触
PSA 与汽车底盘之间没有电流接触
PSA 与汽车底盘之间有电流接触
外壳与汽车底盘之间没有电流接触
外壳与汽车底盘之间有电流接触
外壳与汽车底盘或 PSA 之间没有电流接触，PSA 与汽车底盘间没有电
流接触
外壳与汽车底盘或 PSA 之间没有电流接触，PSA 与汽车底盘间有电流
接触
外壳与汽车底盘间没有电流接触，但与 PSA 之间有电流接触，PSA 与
汽车底盘间没有电流接触
外壳与汽车底盘间没有电流接触，与 PSA 之间没有电流接触，而 PSA
与汽车底盘间没有电流接触
外壳与汽车底盘及 PSA 之间有电流接触
配置
1
2
3
4
5
6
7
8
9
10
表 1. 模块构造和汽车装配可能的配置
在表 1 中，就 BCI 测试的等效 RF 电路而言，配置 1 和 10 代表了两个极限。在配置 1 中，所有的寄生阻抗都是最大
值；而在配置 10 中，它们都是最小值或已经短路。
影响 SASEM EMC 的模块特性
第一项考虑因素是 CBCI 天线和线束之间的电磁耦合。如果 RF 电流 IRF 的频率在 RF 发射 CBCI 天线和被测器件
（DUT）之间的线束段的初始谐振频率的范围内，那么感应电流 IRF_sink（见图 3）就是最大的。感应电流值取决于寄生阻
抗，特别是 ZC_GND。
随着 IRF_sink 的增加，其对被测器件的影响也变得更强。最坏的情况（即最大的射频敏感性）是配置 10，因为 ZC_GND
= 0 欧姆（外壳和车辆底盘间的电流接触）且 ZPSA_C=0 欧姆（PSA 和外壳间的电流接触）。在这种情况下，IRF_sink 只受限
于被测器件的信号路径 VDD、VOUT 和 VSS 相对于外壳的寄生电容（CV+_C，CVOUT_C，和 CV-_C），以及相对于 PSA 的传
感器桥的寄生电容（CS_PSA）。不过，还有一些其他寄生电容（即相对于外壳的内部信号路径）也可能会降低被测器件的
射频敏感性。
示例
•
•
•
DUT=±40mV（标称值）的模拟输出电压所允许的容差
输入信号的有效增益“G”（在 SSC 集成电路的模拟前端进行调节）：G=400V/V
直流桥电阻=4kΩ；在其差分端产生的 AC 桥阻抗=2kΩ
在本示例中，由射频能量所引起的差分桥电压的变化极值是（±40mV/G）=±0.1mV，而所产生的桥分流电流之间差值
的极值是±0.1mV/2kΩ = ± 50nA!
这个非常简单的示例说明了机械结构和所选材料对传感器模块的 EMC 性能的影响。在汽车大批量生产的条件下，考
虑到系统的成本，定义寄生参数要更为困难。
一种有效的设计理念是基于选择不导电材料作为示例压力传感器模块的外壳和压力适配器（PSA）（参考表 1 中的配
置 1）。这种不导电材料确保了 ZPSA_C 和 ZC_GND 取得最大值。但是，为了消除 PCB 的导电结构相对于地的其他寄生电容
的影响，设计必须将模块在车内的装配情况考虑在内。如果被监测系统与其外壳之间的连接也是由不导电材料组成的，那
么寄生阻抗就是最大值。
在 PCB 布局走线时，比较容易确保相对于地的寄生电容 CV+_C，CVOUT_C 和 CV-_C 近乎相等，以使得进入的射频能量
就像是 SASEM 的共模信号。换句话说，在 SASEM 处，没有合适的射频地可用，这使得在被测的宽谱频率范围内阻拦该
射频能量（例如，通过电容）变得几乎不可能。此外，电容不是“理想”元件——它们内部也有寄生参数——特别是其串
联电感（ESL），它决定了电容开始像电感那样起作用的频率极限。典型的 0805 封装 MLCC-X8R 电容的 ESL 是
1~1.5nH。只有通过高的共模抑制比（CMRR），才能实现对所加射频能量的高抗扰性。ZSC31150 可以通过配置保证这一
点。
如果 SASEM 外壳和 PSA 需要用导电材料，所产生的寄生阻抗会更小，而感应射频电流会更大。因为 SASEM 中不同
元器件（即本示例中的外壳、PCB 和 PSA）间存在机械容差，所以在大批量汽车生产的制造条件下，很难确定这些寄生参
数。
这个问题的一种解决方案是，为感应射频电流设计一条从线束到地的通道，它需要靠近传感器系统的信号路径并具有
极低的阻抗。模块的导电外壳可以提供这种通道，并为模块的 PCB 提供针对 GHz 范围内辐射射频信号的屏蔽。采用这种
结构理念的另一优势在于，SASEM 在车内装配的条件无法降低其电磁抗扰性，因为采用这种设计考虑了最坏的情况（参见
表 1 中的配置 10）。
SASEM 的负电源电压与底盘之间不允许有电流接触。在外壳与地之间增加一个具有足够高的额定工作直流电压和承受
高瞬态电压的电容即可以为射频电流提供这样的一条路径。这一解决方案的巨大缺点是必须使用到金属外壳（例如，铝质
外壳）的强韧性以提供长期稳定的电气连接，从而增加了成本。此外，外壳与地之间的电容必须指定相对较高的电压（例
如 500 或 1000V），从而导致更大的封装和更高的成本。
上面讨论的隔直电容（连接在 VDD-VSS 和 VOUT-VSS 之间）的 ESL 以及所导致的对有效频率范围的限制也需要加以
考虑。同样，备选方案是创建一种 PCB 布局走线，针对到 SSC 集成电路的敏感的传感器信号线进行优化，以便通过浮动
的金属外壳为感应射频能量提供高的射频对称性和完全相同的阻抗。这会使得进入的射频能量就像是 SASEM 的共模信号
一样。针对于金属外壳直接放电的 ESD 所需的强韧性（典型要求：自 SASEM 的地算起±15kV）可以通过将应用电路绘制
在 PCB 上以及与金属外壳间的其他适当的隔离来实现。
通过最坏情况下大电流注入测试的模块设计
图 4 演示了基于表 1 中的配置 10，在不使用外壳到地电容的情况下，所生成的面向共模大电流注入（CBCI）的电路。
图 4：基于配置 10 经过优化的传感器模块的 CBCI 测试电路和 EMC 电路
5VDC
Standardized Artificial Network(AN)
1μF
1μh
100Nf(typ.)
Application-Specific Test Network
VDD
VOUT
VSS
DC
BCI Antenna at Varying Positions
Harness(1=1.7m)
Case of the Module
RF
GND=chassis
IRF_sink
PCB
CS_PSA
ZSC31150+ext.caps
PSA
CV+_C
CVOUT_C
CV-_C
直流 5V
标准化人工网络（AN）
1μF
1μh
100Nf(典型值)
专用测试网络
VDD
VOUT
VSS
直流
位置变化的 BCI 天线
线束（I=1.7 米）
模块外壳
射频
地=底盘
IRF_sink
PCB
CS_PSA
ZSC31150+外部电容
PSA
CV+_C
CVOUT_C
CV-_C
通过图 4 中 PCB 上所示的 3~5 个外部电容，可以用配置 10 来实现合适的 EMC 性能。在“最佳情况”条件 1 中，只需
C1、C2 和 C5 即可满足 EMC 要求。这些电容也能够显著降低模块引脚处的 ESD 峰值电压，因此通过>4kV（例如 8kV
ESD）电压的 ESD 测试成为可能。在“最坏情况”配置 10 中，除了 C1、C2、C3、C4 和 C5 之外，可能还需要进行合理的
PCB 布局走线并采用与金属外壳间的合适隔离。
PCB 布局走线对于降低传感器模块的电磁敏感性是非常重要的。电容 C1 和 C2 必须尽可能地靠近线束的末端，而到
SSC 集成电路引脚的走线应该具有几乎完全相等的尺寸。强烈推荐所有连接传感器元件和 SSC 集成电路输入的 PCB 走线
都应当越短越好，越相近越好。电容 C5（如果需要，还有 C3 和 C4）必须放置得尽可能地靠近 SSC 集成电路引脚。所有
这些建议都能够帮助优化 PCB 布局走线的射频共模特性，以实现射频拒绝（RF rejection）。
符合 GMW3097 汽车标准的模块设计
一项严格且有关暂态强韧度的 EMC 标准示例是通用汽车的 GMW3097 标准。这项汽车规范要求系统能防护以电容方
式耦合到供电线上的高达 85V 的暂态脉冲，后者会产生串扰行为。这项规范要求在测试时用 100nF 的耦合电容以串联方式
连接到“尖峰发生器”，后者所产生的一系列 10 个 85V 脉冲会被传输到 SASEM 的线束上。在测试中，SASEM 允许有一
项或多项功能超过规范的极限值；但是一旦测试完成，这些功能必须回到规范。
应用要求规定了为满足GMW3097 规范需要哪些I/O线路。在下面的示例中，由等式 2 确定，我们选择了在图 5 的测试
线路中所示的电路元件值，以便在供电线路（VCC）上满足 85V规范。要在ZSC31150设计中满足这项要求，需要如下的元
器件，因为它的供电引脚VDDE和VSSE以及模拟输出引脚OUT都指定了最大±33VDC的直流过压：
C1 = 220 nF
C2 = 47 nF（推荐值；参考 ZSC31150 的数据手册）
C3 = 100 nF（推荐值；参考 ZSC31150 的数据手册）
C4 = 100 nF
(2)
（2）
其中，在尖峰产生过程中 V1 = 85V，
(3)
在尖峰产生过程中
图 5：示例 GMW3097 EMC 测试设置
Sensor Module
VDDA
VDDE
VSSA
ZSC31150
VSSE
VCC
OUT
GND
Application under Test
VCC
GND
Spike Generator (Impedance ≤2Ω )
面向满足诊断需求的模块设计
传感器模块
VDDA
VDDE
VSSA
ZSC31150
VSSE
VCC
OUT
地
被测应用
VCC
地
尖峰发生器（阻抗≤2Ω）
为了遵从汽车 OEM 厂商“按需维修”的政策，需要 SASEM 提供一系列内置诊断功能，以检验传感器元件，到 ECU
的连接以及内部电子线路的正常工作（特别是 SSC 集成电路）。除了 SSC 集成电路中由其架构所决定的内部诊断以外，
“按需维修”还需要一些常见的诊断功能。
以下诊断功能与传感器元件有关：
•
•
传感器连接检查（考虑走线的短路和断路）
传感器老化检测
对于 SASEM 和 ECU 之间断掉的线束电线的检测，有两种重要的情况：
•
•
电源缺失；即 VCC 线存在断路
地缺失；即地线存在断路
对于这两种情况，必须要确保 ECU 可以检测到输出信号线的这些故障状况。根据 ECU 设置的不同，可能会要求输出
信号通过连接到信号线的 ECU 负载电阻驱动到诊断故障带（DFB）。为启用此设置，在这两种故障情况下，SASEM 的信
号输出必须被驱动到高阻态/低漏电流态。例如，当出现电源/地缺失时，规定 ZSC31150 的输出其输出漏电流在+150°C 时≤
±25µA（在+125°C 下≤ ±12.5µA）。
最佳的独立传感器模块设计
对于 ECU 供电的独立传感器模块，如果其接口采用电阻性的传感器元件并提供比值测量模拟电压输出，那么汽车
OEM 应用的所有技术和商业要求都可以通过深思熟虑的模块设计（特别是 PCB 布局走线）来得以满足，这时需要考虑无
源元器件的真实特性以及所有相关的寄生参数，并利用高性能的 SSC 集成电路（例如 ZSC31150）。
Torsten Herz 是 ZMDI 公司全球现场应用工程组经理
Mehr Power für Pioniere!
Article and interview with Steffen Wollek (ZMDI)
March 2014 in Deutsche Bank_results (Germany), print and digital
18
Finanzierung_Innovationen
Deutsche Bank_r e s u l t s
Mehr Power für Pioniere!
Öffentliche Fördermittel erleichtern Mittelständlern die Produktentwicklung.
Die Hausbank sorgt dafür, dass alles klappt. Angst vor Bürokratie ist dabei unbegründet
FOTOS: CORBIS, FOTOLIA
E
rfolg ist für den Dresdner Halbleiterhersteller ZMDI auch eine Frage der Geschwindigkeit. Im Wettbewerb mit den globalen
Chip-Giganten sucht das Management des Mittelständlers unentwegt nach aussichtsreichen speziellen, innovativen Marktsegmenten. „Dort wollen wir schneller sein als die Großen und diesen
Vorsprung gewinnbringend nutzen“, sagt Finanzvorstand Steffen Wollek. Wichtigstes Produkt von
ZMDI sind energieeffiziente und stromsparende
Chips für Sensoren in der Fahrzeugindustrie, der
Medizintechnik sowie im Industrie- und Consumerbereich. Zu den Abnehmern zählen führende
Unternehmen wie ZF, Continental, Braun, Festo
und Casio.
Mit hohem Einsatz arbeitet das Unternehmen
daran, seinen Vorsprung zu verteidigen. 30 Prozent
des Umsatzes von zuletzt rund 60 Millionen Euro
fließen in die Entwicklung – deutlich mehr als bei
Thesen
Der Staat fördert: Bei der F&E-Finanzierung
stoßen kleinere Unternehmen schnell an
Grenzen. Deshalb bieten EU, Bund und Länder
eine Fülle von Förderprogrammen.
Die Bank hilft: Viele Unternehmen schöpfen
diese Möglichkeiten nicht aus. Dabei kann
gerade die Bank ihnen helfen, ohne großen
Aufwand an Förderung zu kommen.
Die Bürokratie schrumpft: Ein neues
Programm des Europäischen Investitionsfonds, das die Deutsche Bank als Erste
seit Anfang vorigen Jahres vermittelt, kommt
gezielt Unternehmen mit weniger als
500 Beschäftigten zugute.
der Konkurrenz, die laut Wollek im Schnitt 18 bis
20 Prozent investiert. Dabei ist Geduld gefragt.
„Die meisten Projekte sind langfristig“, sagt Wollek.
„Vom Beginn der Entwicklung bis zur Erzielung der
ersten Umsätze dauert es mindestens zwei Jahre,
und die Innovationszyklen werden immer kürzer.“
Für einen langen Atem sorgen nun unter anderem
staatliche Fördermittel.
Ob Bund, Land oder EU – Unterstützung durch
die öffentliche Hand trägt entscheidend dazu bei,
dass der Mittelstand seine Innovationskraft voll
entfalten kann. „Bei der Finanzierung von Forschung und Entwicklung mit Eigenmitteln stoßen
vor allem kleine Unternehmen an Grenzen“ – so
lautet das Fazit einer Studie des Deutschen Instituts für Wirtschaftsforschung (DIW). Allein über
Kredite lassen sich die F&E-Kosten aber häufig
nicht finanzieren, da deren Erfolg schwer prognostizierbar ist. Die Lücke schließen dann die
öffentlichen Programme als „wichtige zusätzliche
Finanzierungsquelle“.
Die Praxis zeigt jedoch, dass gerade mittelständische Firmen die Möglichkeiten oft nicht
nutzen – weil sie diese entweder nicht kennen
oder bürokratische Hindernisse fürchten. „Dabei
bietet Innovationsförderung die Chance, die F&E
finanziell zu beschleunigen und bei Erfolg die Wettbewerbsfähigkeit des Unternehmens entscheidend zu stärken“, sagt Sabine Tieves, Leiterin für
Öffentliche Fördermittel bei der Deutschen Bank.
Keine Einzelnachweise mehr nötig
Bei der Suche nach passenden Fördertöpfen kann
die Hausbank die Rolle des Wegweisers übernehmen. So war es im Fall von ZMDI. Seit dem
vergangenen Jahr setzt das Unternehmen Mittel der Europäischen Investitionsbank (EIB) ein,
und zusätzlich unterstützt der Europäische
Video
19
20
FOTOS: ZMDI (2)
„Das unbesicherte KfW-Darlehen
ist Eigenkapital auf Zeit“
ZMDI: Europa hilft forschen
Für den Sensorspezialisten ZMDI sind Fördermittel ein wichtiger Baustein der Innovationsstrategie. 30 Prozent des Umsatzes investieren die Dresdner in F&E. Auch die Programme der staatlichen Förderbank KfW hat Finanzvorstand Steffen Wollek (Foto) im Blick.
Aktuell setzt ZMDI auf Mittel der Europäischen Investitionsbank sowie des Europäischen
Investitionsfonds, der innovative Mittelständler mit bis zu 500 Mitarbeitern mit Garan-
Entwicklung mit Staatshilfe
FOTOS: FRIEDOLA TECH (2)
tien unterstützt. „Vor allem die langfristige Ausrichtung hat uns überzeugt“, sagt Wollek.
Friedola Tech: Recycling macht stark
Beim Kunststoffhersteller Friedola Tech wird schon in der Entwicklung dafür gesorgt, dass
auch das Recycling optimal funktioniert. „Wir verstehen uns als Greentech-Unternehmen“,
sagt der kaufmännische Leiter Werner Eisenhardt (Foto). Logistiker und Autohersteller
sind wichtige Kunden der Thüringer – sie legen viel Wert auf Leichtbau, um die CO2-Bilanz
zu senken. Auch darauf muss Friedola Tech bei Innovationen achten. Unterstützt von
der Europäischen Investitionsbank entstand eine neue, leistungsfähige Laminieranlage.
Investitionsfonds (EIF) die Finanzierung mit
einer 50-Prozent-Garantie. „Die Deutsche Bank hat
uns das Programm vorgeschlagen, das wir dann
aus einer Reihe von Instrumenten ausgewählt
haben“, sagt Steffen Wollek. ZMDI profitiere nun
von günstigen Zinsen und mehr Finanzierungsspielraum. „Vor allem aber hat uns die langfristige
Ausrichtung überzeugt.“ Über fünf Jahre läuft die
Förderung – die ersten zwei Jahre sind tilgungsfrei. „Das ist angesichts der herrschenden Innovationszyklen für uns wichtig“, sagt Wollek. „Es geht
darum, nachhaltiges Wachstum abzusichern und
nicht nur eine kurzfristige Unterstützung des operativen Geschäfts.“ Denn das Ziel von ZMDI lautet:
„Wir wollen weiter wachsen.“ In den USA und Asien
hat das Unternehmen schon Standorte aufgebaut.
Der Zugang zu den Garantien des Europäischen
Investitionsfonds wird für Unternehmen wie ZMDI
einfacher, da die EIB-Tochter nicht nur einzelne Projekte unterstützt. Firmen mit bis zu 500 Beschäftigten weisen nun anhand von einfachen Kriterien
nach, dass sie innovativ sind, um die Garantie zu
erhalten. Die Deutsche Bank ist hierzulande das
erste Institut, das dabei mit dem EIF kooperiert.
Unterstützt dieser ein Unternehmen, senkt das
die Risiken – Kredite können so zu günstigeren
Konditionen vermittelt werden.
Ergänzend wirkt das ERP-Innovationsprogramm
der staatlichen Förderbank KfW – es begünstigt
Mittelständler bei Investitionen in Neu- und Weiterentwicklungen. „Hier wird nicht das Unternehmen als solches gefördert, sondern ein spezielles
förderfähiges Projekt. Dabei ist eine umfassendere
Dokumentation erforderlich“, sagt Sabine Tieves.
Der Einsatz kann sich freilich lohnen. „In Bezug auf
die Zinsen ist es eines der günstigsten Angebote.
Zudem kann ein unbesichertes Nachrangdarlehen gewährt werden, es ist Eigenkapital auf Zeit.“
Für results haben die Fördermittel-Experten der
Deutschen Bank die wichtigsten Förderinstrumente für Mittelständler analysiert (Tabelle Seite 22).
Enge Kooperation mit den Kunden schon im Entwicklungsprozess – nach diesem Prinzip arbeitet
der thüringische Kunststoffspezialist Friedola
Tech. „Wir verstehen uns als Innovationstreiber für
die Logistik und die Fahrzeugindustrie“, sagt der
kaufmännische Leiter Werner Eisenhardt. Leichtbau und Wiederverwendungsfähigkeit nennt er als
zentrale Kriterien der Entwicklungsarbeit seines
Unternehmens.
„CON-Pearl“ heißt ein Kunststoffmaterial von
Friedola Tech – Hohlkammern machen es besonders leicht, eine Glasfaserverstärkung sorgt für
hohe Stabilität. CON-Pearl ist die Basis für zahlreiche Produkte des Unternehmens. Ein Beispiel: Kofferraumböden für einen deutschen Autohersteller.
„Wir haben 2012 das gemeinsame Entwicklungsprojekt vorgeschlagen“, sagt Eisenhardt. In diesem
Fall kamen die Partner auch ohne Innovationsförderung ans Ziel – heute liefert Friedola Tech die
gesamte Kofferraumauskleidung.
Öffentliche Mittel setzt das Unternehmen
dagegen ein, um sein Grundprodukt zu verbessern – eine neue Laminieranlage soll die Produktionskapazität verdoppeln. „Wir arbeiten in diesem
Zuge auch an neuen Eigenschaften des Materials“,
sagt Eisenhardt – feuerhemmend und leitfähig soll
es sein. „Das lässt sich mit der neuen Anlage besonders gut machen.“ Rund sechs Millionen Euro
28,6 %
aller mittelständischen Unternehmen in Deutschland
stützen sich bei der Finanzierung
ihrer F&E-Aufwendungen auf
öffentliche Fördermittel,
ergab eine Umfrage des DIW.
Quelle: DIW Berlin; 1391 Unternehmen befragt;
Mittelwerte in Prozent
investiert Friedola Tech. „Dem gegenüber steht ein
Produktionswert von rund 25 Millionen Euro pro
Jahr“, sagt Eisenhardt. Wichtigster Abnehmer ist
die Logistikbranche – Friedola Tech produziert für
sie Transportbehälter für Schüttgüter, etwa Granulate. Gefördert wird das Projekt wie bei ZMDI
über EIB und EIF – auch Friedola Tech mit seinen
rund 400 Mitarbeitern erhält so einen günstigen
Zinssatz. „Wir haben mit der Bank eine umfangreiche Marktstrategie ausgetauscht und verschiedene Anwendungsfelder für unsere Innovationen
aufgeführt“, erläutert Eisenhardt. „Wir sind jetzt
insgesamt als innovatives Unternehmen eingestuft. Spezielle Projekte zu zeigen, war deshalb
nicht nötig.“
Parallel zur EU bieten auch Bund und Länder
Unterstützung für forschungsstarke Mittelständler. Auf dem Weg zu internationalen Märkten nutzt
die Montanhydraulik AG in Holzwickede günstige
Darlehen der NRW.BANK. Fünf Jahre Laufzeit, ein
Zins von gerade einmal 1,45 Prozent – „das ist für
uns äußerst vorteilhaft“, sagt der kaufmännische
Geschäftsführer Josef Mertens. Das Geld trägt
dazu bei, eine neue Drehmaschine zu finanzieren,
mit der Montanhydraulik weltweit neue Kunden
erschließen will. Kostenpunkt: 1,5 Millionen Euro.
Staat beteiligt sich an Risiken
Das seit 60 Jahren familiengeführte Unternehmen
arbeitet in großen Dimensionen: In Staudämmen
und Schleusen oder mobilen Kränen kommen Hydraulikzylinder der Westfalen zum Einsatz – zuletzt
erwirtschaftete Montanhydraulik mit weltweit
1100 Mitarbeitern etwa 225 Millionen Euro Umsatz. Dank der neuen Produktionsanlage sind noch
mächtigere Varianten möglich. Die 28 Meter langen
Zylinder werden auf Öl-, Gasplattformen und Bohrschiffen eingesetzt. „Die Maschine ist vom Grundkonzept her keine Innovation“, erläutert Mertens.
„Aber sie versetzt uns in die Lage, ein innovatives
Produkt herzustellen, das speziell auf den jeweiligen Kunden zugeschnitten ist.“ So kann künftig ein
weltweit führender Hersteller von Geräten für die
Gas- und Erdölexploration beliefert werden.
Bei Montanhydraulik wird nicht nur der Entwicklungseinsatz mit Mitteln der NRW.BANK belohnt. Es gibt am Produkt einige Verbesserungen,
etwa bei der Steuerung. „Die neue Maschine ist
beim Stromverbrauch deutlich günstiger als ihr
Vorläufer“, sagt Mertens. Der Einsatz für eine
bessere Energiebilanz öffnete den Weg zu einem
weiteren Fördertopf, der Investitionen in
21
Niedrige
Zinsen dank
EU-Garantie
Deutsche Bank stellt bis zu
120 Mio. Euro zusätzlich bereit
Mit einem Garantieprogramm unterstützt der
Europäische Investitionsfonds (EIF) Firmen, die weniger als
500 Beschäftigte haben. „Risk Sharing
Instrument“ heißt die neue Form
der Risikobeteiligung. Binnen zwei
Jahren kann die Deutsche Bank als
erster Partner des EIF in Deutschland
innovativen Unternehmen dank einer
50-Prozent-Garantie bis zu 120 Millionen Euro an zusätzlichen Mitteln zu
günstigen Konditionen bereitstellen.
Der EIF deckt bei Zahlungsverzug oder
-ausfall 50 Prozent des ausstehenden
Kreditbetrags. „Damit ändert sich die
Risikobetrachtung fundamental“, sagt
Johannes Winkler, Experte für öffentliche Förderung bei der Deutschen Bank.
Mit dem Programm verbunden ist ein
Umsteuern der EU bei der Förderung.
Unternehmen müssen nicht mehr einzelne Projekte dokumentieren, sondern
nur eines von mehreren Kriterien erfüllen, um als innovativ kategorisiert zu
werden und so Zugang zu den Mitteln
zu erhalten. Dazu zählt unter anderem
der Sitz in einem Technologiepark,
die Registrierung eines Patents oder
der Erhalt eines Innovationspreises
innerhalb der vergangenen 24 Monate.
WEITERE INFORMATIONEN
Kontakt: Ihr Kundenbetreuer.
Europäische Investitionsbank:
www.eib.org
Förderung des Europäischen Investitionsfonds: www.eif.org
Innovationsförderung der KfW für den
Mittelstand: www.kfw.de, Stichwort
„Mittelstandsförderung“
22
„Förderung ist wichtig, weil wir die Arbeit
nicht sofort in Umsatz ummünzen können“
eine höhere Effizienz unterstützt. Lange
habe das Unternehmen ganz ohne öffentliche Unterstützung gearbeitet. „Wir reinvestieren immer
einen Großteil der Gewinne in die Firma“, erläutert Geschäftsführer Mertens. Die internationale
Expansion aber habe Mittel erfordert, die allein mit
Bordmitteln nicht zu stemmen waren.
„Die Bank hat die Rolle des Initiators übernommen, den gesamten Prozess begleitet und auch
die bürokratischen Formalitäten übernommen“,
sagt Mertens. Er ist überzeugt, dass sich der Einsatz für sein Unternehmen und den Standort
gleichermaßen auszahlen wird. „Bislang gab es
weltweit nur wenige Unternehmen, die solche
Zylinder herstellen konnten. Nun können wir in
den Wettbewerb einsteigen.“ In Indien beispielsweise will Montanhydraulik das Geschäft ausbauen. „Dort wird stark auf Stromerzeugung aus
Wasserkraft gesetzt“, sagt Mertens. „Für die Betätigung der Schleusentore sind Großzylinder nötig.“
Er erwartet, dass die neuen Hydraulikzylinder mit-
telfristig zehn bis 15 Prozent zum Gesamtumsatz
des Unternehmens beisteuern können. „Auch in
Südamerika gibt es großes Potenzial für uns“, sagt
Mertens. „Allerdings sind große Investitionen nötig, um dort Fuß zu fassen. Es funktioniert nur mit
einem Partner vor Ort.“
Innovation und Internationalisierung – auch
bei pfm medical ist beides eng verwoben. Stetig
hat der Kölner Medizintechnikhersteller den Auslandsanteil am Umsatz gesteigert, zuletzt lag er bei
gut 40 Prozent. Tendenz: weiter steigend. Die Produktpalette ist breit: Skalpelle, Beatmungsmasken,
chirurgische Implantate sowie Produkte für das
Therapiemanagement zählen dazu. Für Wachstum
sorgen vor allem die entwicklungsintensiven Produkte – neben den Implantaten sind das Produkte,
die bei Herzoperationen zum Einsatz kommen. Um
13,6 Prozent stockte pfm medical 2012 seine F&EAusgaben auf. „Das ist bei uns sehr langfristig ausgerichtet“, sagt Finanzvorstand Reinhard Blunck.
„Da ist Förderung besonders wichtig, weil wir die
Ausgewählte Konzepte zur Innovationsfinanzierung über öffentliche Fördermittel für den Mittelstand
Förderung
Instrument
Globaldarlehen
der Europäischen
Investitionsbank
das
innovative
Projekt
diverse Förderprogramme der KfWBankengruppe
diverse Förderprogramme der Landesförderinstitute
das
innovative
Unternehmen
Garantie
des Europäischen
Investitionsfonds
Wirkung
Günstigere Kundenzinssätze (gegenüber normaler
Bankfinanzierung)
führen zu verminderten Zinsbelastungen für den Kunden.
ergänzt andere bankübliche Sicherheiten
des Kunden und führt
zu einer Verringerung
des Risikopreises
Finanzierungsvolumen pro Vorhaben
Varianten
antragsberechtigte
Unternehmen
bis
12,5 Millionen Euro
Kombination mit
der Garantie des
Europäischen
Investitionsfonds
< 3000
Beschäftigte
in der Regel bis
5 Millionen Euro
MezzanineTranchen
bis 500 Millionen
Euro Umsatz
in der Regel bis
10 Millionen Euro
Haftungsfreistellungen
in der Regel
bis 500 Millionen
Euro Umsatz
bis
7,5 Millionen Euro
Kombination
mit dem Globaldarlehen der
Europäischen
Investitionsbank
< 500 Beschäftigte
Zugang
Zugang zu allen
hier genannten
Finanzierungsmöglichkeiten
vermittelt der
Firmenkundenbetreuer.
Darüber hinaus
bestehen weitere
Finanzierungsmöglichkeiten für
Innovationen z. B.
über Zuschüsse
oder Eigenkapital.
Wichtig: In vielen Fällen muss die Beantragung von öffentlichen Fördermitteln vor dem Beginn der Investition erfolgen.
Arbeit nicht so schnell in Umsatz ummünzen können.“ Der Staat trägt so einen Teil der Risiken, die
das Unternehmen nicht allein eingehen könnte.
Zehn bis 15 Prozent der Produkte seien jünger als
fünf Jahre. Rund 85 Millionen Euro Umsatz erzielte
das Unternehmen 2012.
Die zunehmende Bedeutung von Forschung
und Entwicklung spiegelt einen Strategiewechsel.
Von einem Handelsunternehmen für Medizinprodukte wandelt sich pfm medical zunehmend zum
Produzenten. „Wir wollen unabhängiger sein“,
sagt Blunck. Eigene Patente sind hier die Basis
für den künftigen Markterfolg.
23
FOTOS: MONTANHYDRAULIK GMBH (2),
Montanhydraulik: Neue Maschinen
Es zählt jeder Meter: Ein norwegischer Kunde fragte an, ob Montanhydraulik für Öl- und
Gasplattformen auch 28 Meter lange Hydraulikzylinder herstellen könne. Eine ganz
neue Maschine musste her, um den Wunsch erfüllen zu können. Die nötige Investition hat
das westfälische Unternehmen mit Unterstützung der NRW.BANK gestemmt. „Das bringt
uns bei der internationalen Expansion voran“, erläutert der kaufmännische Geschäftsführer
Josef Mertens (Foto).
Das Unternehmen strebt in Segmente, die für
Konzerne und Branchengrößen ein zu geringes
Umsatzvolumen bieten. „Wir wollen nicht mit den
ganz Großen in Wettbewerb treten.“ Als Beispiel
nennt Blunck Schneidewerkzeuge für spezielle
Gewebeanalysen. „Unser Umsatz beträgt hier
17 bis 18 Millionen Euro – das entspricht einem
Marktanteil von 90 Prozent. Für Großkonzerne ist
das nicht interessant.“ Bei der Forschung sieht er
Familienunternehmen im Vorteil, weil das Management in der Regel weniger kurzfristig orientiert sei.
Ein Nachteil seien dagegen die eingeschränkteren
finanziellen Mittel.
„Bei der Finanzierung gehört immer eine Bank
dazu, die weiß, wo die relevanten Fördertöpfe
sind“, sagt Blunck. „Das ist für uns als Mittelständler entscheidend, weil wir im Unternehmen niemanden haben, der sich allein darum kümmern
könnte.“ Lang habe es eine „gewisse Aversion“ in
Bezug auf öffentliche Förderung gegeben. „Es hatte sehr viel mit Steuerung und Bürokratie zu tun,
zum Teil ging es um tiefgreifende juristische Fragen“, sagt Blunck. „Zudem war die Förderung oft
zu stark auf Großunternehmen ausgerichtet.“ Das
habe sich inzwischen glücklicherweise geändert.
„Zunehmend müssen wir feststellen, dass sich das
gemeinsam gut managen lässt.“
T H OMA S MERSCH
FOTOS: PFM MEDICAL AG (2)
Familienunternehmen haben Bedarf
pfm medical: Forschung mit Geduld
EU, Bund, Länder – innovative Unternehmen, die öffentliche Förderung nutzen wollen,
finden eine Reihe von Anlaufpunkten. Für den Kölner Medizintechnikhersteller pfm medical
bot ein Zuschuss der EU die richtige Förderung. Rund 34 000 Euro flossen in Forschung
und Entwicklung. Solche Förderung ist wichtig: „Unsere Forschung ist langfristig
ausgerichtet, wir können die Arbeit nicht immer schnell in Umsatz ummünzen“, sagt
Finanzvorstand Reinhard Blunck (Foto).
ZMDI RELEASES THE ZSSC416X SENSOR
SIGNAL CONDITIONER FAMILY
Press Release for the product release ZSSC416x
July 2014 on industryeurope.net
ZMDI RELEASES THE ZSSC416X SENSOR SIGNAL
CONDITIONER FAMILY
09/07/2014
ZMD AG (ZMDI), a Dresden-based semiconductor company that specializes in
enabling energy-efficient solutions, today announces the ZSSC416x, the first in
ZMDI’s series of next generation of sensor signal conditioners. As a global supplier of analog and mixed-signal solutions for automotive, industrial, medical, information technology and consumer applications, ZMDI is pleased to introduce
a state-of-the-art sensor signal conditioning family capable of measuring single,
dual or differential bridge inputs and internal or external temperature sensors.
With a wide analog pre-amplification range, the ZSSC416x family is capable of
highly accurate amplification and sensor-specific correction for most resistive
bridge sensors as well as thermocouple readings. Measured values are provided via the digital SENT 3.0 output or I2C™ (trademark of NXP).
“The ZSSC416x is the first series of products from ZMDI’s Next Generation
Sensor Signal Conditioner Family designed for ease of integration into our
customers’ sensor platforms without sacrificing the performance and flexibility
needed for the lowest possible system costs,” stated Steve Ramdin, Global
Product Line Manager for Multi Market Sensor Platforms at ZMDI. In addition to
the highest proven performance needed for future products, ZMDI’s Next Generation Sensor Signal Conditioner Family ICs offer customers ease of use with
a wide range of predefined signal processing configurations and flexible input
pin selection for quick integration in a wide variety of applications. Mr. Ramdin
added, “Our goal is to make it easy for our customers to build flexible sensor
platforms, quickly and at the lowest possible system costs.”
Features
• Full SENT Rev 3.0 compliance
• Two full bridge sensor inputs; configurable for single, dual or differential
measurements
• Internal and external temperature sensing
• Supply voltage range: 4.75V to 5.25V
• Overvoltage protection to +/- 18V
• ADC resolution: 12 to 18 bit
• Output resolution: 12 bit via SENT and up to 16 bit for I2C™
• Designed for ASIL B requirements in safety-relevant applications
• Temperature range:-40°C to 150°C
• Flexibility for end applications (e.g., additional NTC linearization, algorithms
for HTS sensors, calculation of mass flow)
• Standardized pin layout for family ICs facilitates platform designs
With built-in overvoltage and reverse polarity protection, excellent electromagnetic compatibility and built-in diagnostics features, the ZSSC416x family is
optimized for safety critical applications and harsh environments.
Availability and Pricing
The ZSSC416x family will be available for mass production in December 2014;
however, interested customers can receive samples and pricing today by contacting ZMDI or their distribution partners directly.
Contact Name:
E-Mail Address:
Phone Number:
(
)
Distributor/Rep. Firm:
Global Headquarters
Grenzstrasse 28
01109 Dresden
Germany
Central Office
Phone+49.351.8822.306
Fax +49.351.8822.337
European Technical Support
Phone +49.351.8822.7.772
Fax +49.351.8822.87.772
European Sales (Stuttgart)
Phone +49.711.674517.55
Fax+49.711.674517.87955
.com
Zentrum Mikroelektronik
Dresden AG, Japan Office
2nd Fl., Shinbashi Tokyu Bldg.,
4-21-3, Shinbashi, Minato-ku,
Tokyo, 105-0004
Japan
Phone +81.3.6895.7410
Fax +81.3.6895.7301
ZMD America, Inc.
1525 McCarthy Blvd., #212
Milpitas, CA 95035-7453
USA
Phone 1.855.275.9634 (USA)
Phone+408.883.6310
Fax+408.883.6358
Zentrum Mikroelektronik Dresden AG,
Korea Office
U-space 1 Building
11th Floor, Unit JA-1102
670 Sampyeong-dong,
Bundang-gu, Seongnam-si,
Gyeonggi-do, 463-400
Korea
Phone +82.31.950.7679
Fax
+82.504.841.3026
ZMD Far East, Ltd.
3F, No. 51, Sec. 2,
Keelung Road
11052 Taipei
Taiwan
Phone +886.2.2377.8189
Fax +886.2.2377.8199
v2.06/14

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