LM2852: LM2852XMXA-3.3 output +5V

Hello Eddie,

thanks for reaching out in E2E.

I'm not aware of a condition in which the LM2852XMXA-3.3 may output 5V.

Do you know how much load current is flowing during startup?

It would also help for analysis to see a waveform of the SW pin voltage together with VIN and VOUT during startup.

When you say "sometimes customer power on LM2852XMXA-3.3 will output 5V", does it mean repeatable on some devices, or for some power-up trials on the same device? If on the same device, can it recover in the next trial?

What is the failure rate?

I'm not sure if a floating SNS pin could cause a too high output voltage. Maybe it is worth to check the SNS pin and SGND for proper soldering.

Please let me know your feedback.

Best regards,

Andreas.

Hi Andreas, 

Customer only find one device output 5V randomly.  They are concern the 5V randomly output may also happen on other devices. 

Customer would like to know what conditional LM2852XMXA-3.3 may output 5V?

Thanks & regards

Eddie

Hi Eddie,

thanks for your feedback.

I was suspecting a permanent damage (short between VIN and SW). But if it is occurring only occasional then I don't have any idea what could have happened.

Anyway, at the moment it is only guessing. It would be better to collect more information of the fail scenario in order to really understand the issue. As said, SW signal and load current waveform during startup of a 5V output case would be a first step to analyze.

In addition we could check the layout in order to rule out a layout mistake.

Best regards,

Andreas.

Hi Andreas, 

Do you think we can ship this device through CRP for analysis?

Thanks & Regards

Eddie

Hi Eddie,

I'm afraid that we cannot reproduce the issue. At the moment the customer knows best how to reproduce the issue. I think it would be more helpful if the customer could collect more debug information. Also a ABA swap of the IC (exchanging the IC with a known good board) would help to rule out assembly issues upfront.

Best regards,

Andreas.

Hi Andreas, customer on

Customer did ABA swap and the output (5V/3.3V) are random. 

customer only find one device (from 750 pcs) has this issue. Is there something we can check with customer to find the root cause?

Thanks & Regards

Eddie

Hello Eddie,

thanks for the update.

For the ABA swap, does this mean on the known good board the output 5V/3.3V is random, but was stable and correct before.

Did the customer also try to place a known good device on the problematic board?

As said before, SW1,SW2 pin signal waveform together with the load current during the 5V output case would help to analyze the issue further.

Best regards,

Andreas.