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STM32F407 clock problem? on production boards.

Question asked by pirie.russell on May 2, 2013
Latest reply on May 6, 2013 by jj.sprague

I have a production board that I have currently produced 200 Units, the board uses a STM32F407VET6 and all 200 units work great!

I have just had another batch made up. I have tested 3 so far and 2 have died after 5min! They don't totally die but seem to stop using the external 8mhz crystal and use the internal oscillator, as I have put a scope on the external crystal and its dead.

The two 'dead' ones now seem to run the firmware at like a 3rd of the normal speed. To the point the DFU does not work any more. So I can not connect them to the pc to load new firmware on.

I'm not sure what has gone wrong on these boards? I did notice I used a different load capacitor for these new 200 boards to the previous ones. Could this upset the clock to a point it stops working? If so how come it works for a bit then dies? And when it dies it stays dead. No matter how many times I power cycle it, it remains in this 3rd speed mode.

Have these new load caps damaged the stm32 chip? Or have a received a dodgy batch of stm32's

I'm really confused to why my boards are dying and am not really sure what direction to go in to repair them?

Any help would be really appreciated.