Electronic – STM32 reset not work

resetstm32

Background:
1.5% of products which use STM32F107 didn't work after using 3 months; Lithium battery is the power supply source. The products were used in car. This phenomenon suddenly occured without any pridication. According the record in product, the temperature is normal(25 Centigrade).

Problem Analysis:
The voltage at VDD is 3.3V. The NRST reset do not work. After disconnecting the power and connecting again, the chip could recover and work again. And this problem could not be reproduced in our lab condition.

Additional information: the chip use STANDBY mode to shut down and use WAKE UP pin back to work.

The schematic is attached below.(Only the core components displayed)

Is the schematic wrong or did I missed something?
schematic picture

Best Answer

As I said in my comment, I'm not convinced that the true "failure mode" has been defined - "dead" does not appear correct.

However I have found one error in the design, from the excerpt of the schematic supplied - \$\small V_{BAT}\$ is not connected. I'm checking the docs now, but I believe that is required. From memory, failure to reset properly is one possible side-effect. More to follow...


Update: From the STM32F107 reference manual, they say it is "recommended" that \$\small V_{BAT}\$ is connected to \$\small V_{DD}\$ (and decoupled). I seem to remember rare reset-related issues without this connection, but I'm away from my notes so don't have more details.

STM32F107 reference manual section 5.1.2

The same advice is given in Application Note AN2586 - Getting started with STM32F10xxx hardware development:

AN2586 - Getting started with STM32F10xxx hardware development

I'm not convinced about the analog filter in the schematic, as Marko has mentioned and, as Lorenzo has said, not being able to reproduce your problem in the lab is telling you something. Something is different (e.g. power quality, user behaviour, EMI, shielding etc.) between your lab test procedure and/or your lab environment, and the environment where the units "fail" (in whatever way that "failure" is eventually defined).

One more thing: Your external components attached to nRST don't match the recommended configuration by ST (you've got an external pull-up resistor which they don't recommend). I am not saying that this is causing a problem - just that it may need further review.

However I have run out of time for now. Hope this info helps.