we designed a STM32F429ZGT6 board. We're using a RTC and integrated a battery. We produced in a first batch of 50 of these boards and observed a strange behavior on 8 of these 50 boards.
These boards are booting and behaving "normal" when a battery is plugged in.
When we remove the battery the boards are not working any more. We tracked down the problem to the LSE clock configuration in the SystemClock_Config function If we don't configure the LSE clock the faulty boards are booting too.
We checked the external circuits and the components, everything seems fine. The problem is also not occuring when debugging the board with a debugger.
We checked the errata doc but did not find any hint.
I also attached a screenshot of the schematic.
Any help would be very appreciated.