Quality Notification - TI E2E Community

Quality Notification
TPS54335DDA, TPS54336DDA, TPS54335DRC, TPS54336DRC
Abnormal Output Switching after EN Transitions Low
Dear Customer,
Texas Instruments (TI) strives to comply with the strictest quality standards and processes to provide the
highest quality products to TI customers. This letter serves to formally notify you that TI has identified
the following potential issues on certain TI devices.
Texas Instruments appreciates your business and apologizes for any inconvenience this may cause. We
are ready to work with you to minimize any problems this potential issue might cause. Please feel free to
contact us, or your field sales representative, if you need more information.
ISSUE DESCRIPTION:
Issue #1
TI has found that a high percentage of TPS54335 and TPS54336 devices produce unwanted switching
after the enable pin (EN) transitions to logic-low, when a continuous voltage input (VIN) supply is
present. This symptom shows VIN dependency:
 When VIN is below 20V, a small number of unwanted pulses may rarely occur after EN
transitions low. Refer to Figure 2.
 When VIN is 20V or higher, there are some devices that exhibit continuous switching after EN
transitions low. This switching may continue until the VIN supply is disabled. Refer to Figure 3.
Figure 1 Good Unit (1ms/div)
Figure 2 Bad Unit (1ms/div)
Figure 3 Worst Case Unit (1s/div)
Issue #2
TI observed unwanted switching with brief shoot-through current after EN is turned to low while Vin is
kept alive. This could potentially damage the device after a large number of cycles of the EN pin. This
issue shows strong dependence on the Vin supply voltage and the output switching frequency (Fsw).
The risk is believed to be low in many conditions, but it is recommended to review your application with
TI to determine the impact. Further evaluation is in progress to characterize this behavior to fully
understand the issue under different conditions.
PAGE 2
ROOT CAUSE:
The enable control logic circuitry inside TPS54335 and TPS54336 is designed to operate with multiple
power rails and one of these power rails has the potential to get into a floating condition when EN=L and
VIN is still ON. Until this floating power rail is discharged by parasitic resistance components, this logic
circuitry cannot process the EN pin logic state correctly resulting in the abnormal switching on the device
output.
CORRECTIVE ACTION:
8D investigation is currently ongoing and will provide corrective actions in response to root cause. TI has
finalized a permanent solution and a product design revision has been developed to completely resolve
this issue for all affected devices in future material. The new die revision is estimated to release to
production by April 2015.
DISPOSITION:
Please immediately review your application for potential impact. If application conditions match those
described in the Issue Description, please notify TI to review your application for potential risk. TI is
placing the affected devices on shipment hold pending your review and acceptance of the disclosed
issues.
Thank you for your co-operation,
Matt Sunna
Texas Instruments Inc.
PWR Customer Quality Engineer