PCF2127 Randomly Locking up

[dave_harmonjr]

On a new set of boards produced by our vendor after anywhere from instantly to a few days the RTC will lock up. Same firmware, new batch of chips, old ones do not have this problem.

Bad System:

PCF2127T – AFR680 – 1   10 – knD20322

M41W – 9VT4 – 1N16S – CTMJ7B

Good System:

PCF2127T – AFF949 – 1   05 – kn19342

M41W – 9VT4 – 1N16S – CTHHQQ

Also just to be clear I have no idea if the uC has anything to do with it I just am listing it for reference as a part of the system.

By lock up I mean it no longer responds to commands and returns 0xFF for all bytes on the MISO line which causes our product to be unable to properly function. If anyone could help that would be awesome, this is a frustrating issue. The processor we are using with it is a KW41Z and using the SPI SDK. On that same SPI bus we have an analog devices DDS Chip and it functions perfect while this PCF2127 is constantly locking up.

Here is the schematic of the chip:

If there is any other things I can check or share let me know, Thanks!

[JozefKozon]

Dear Dave,

could you please confirm, that both batches were bought from one of our authorized distributors? Please see this link for a list of authorized distributors.

With Best Regards,

Jozef

[dave_harmonjr]

According to the board house the chips came from Digikey.

[JozefKozon]

Hi Dave, 

have you tested the known good chip on the failing board and vise versa? You probably already have, but in case you haven't could you please try the Part Failure Verification: A-B-A Swap Method. Please see this link. 

Please find attached an example code for the PCF2127. Could you please test it with your boards?

With Best Regards,

Jozef

[dave_harmonjr]

I am working on this FYI. It is a little time consuming because I cannot figure out how to trigger this problem and thus am waiting for it to occur on some boards. I am doing the swap today and will report back on the results. Thank you for your suggestion.

[JozefKozon]

Hi Dave,

you are very welcome. 

With Best Regards,

Jozef

[dave_harmonjr]

After doing ABA swap the old board with new chip has frozen like the new batch of boards started doing.