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UCC28740: UCC28740 start up issue

Part Number: UCC28740


The UCC28740 is the below situation. The schematic is the same as the TI reference design.

There are currently about 500/15000 fail rate

When 90VAC, use end customer-customized FCT equipment for test verification. UCC28740 is not functioning correctly. But when the voltage was raised to 95VAC, the IC that was not working correctly could work normally again. In the past, there was no problem with sending 90VAC during the test. This time, there were a lot of ICs that could not function normally under this condition, so I would like to ask TI for assistance.

1. There are three kinds of data codes in the photo, do these three data codes have problems in the FCT test => yes
2. Please verify whether it is normal on the bench => If the IC of PASS and the IC of NG are exchanged for verification, the original PASS board will become NG, and the original NG board will become PASS
3. Is the data code of the IC that has been tested without problems the same? = According to the text of the IC body, I can't tell which data code the code is produced by the IC, I can only verify it by exchanging PASS with NG IC
4. Has the transformer been exchanged with the tested OK machine before? => Tried to replace the PASS transformer, but it is still NG.


  • Hi Rock,

    Thank you for the inputs and observations. The EVM board has been tested between 85V to 265Vrms, hence there should not be any issue with operating with operation at 90 or 95Vrms.

    I am not sure on the three data code on the IC and what it signifies, probably could be related to the production lot. I will reach out to the prodct/ package team to see  what it means but this TI coding could be confidential to share on e2e without an NDA with customer. I can confirm on this.

    Just to confirm, do you have 3 data codes in the 15000 samples and 500 samples of a particular data code fail or is it random with the failure observed in multiple data codes?  Also if you can share data on the error (type of failure) which the customer gets with the faulty sample.