Stm32WB55 loses connection due to power issues.

[Taxara]

Hi all,

I have the STM32WB55 board connected to a battery. However it loses connection (firmware does continue without issues) quite often. After some research I have found out that when i attach the charger or the st link the disconnection issue is gone. Leading me to believe that the battery isn't capable of supplying enough for the system + ble when transmitting.

So I've added a 36uF polarized capacitor on the 3v3 of the arduino morpho connector to provide for the peaks. This does solve the problem as well.

Now the question:

How big a capacitor do I need to be able to transmit data without losing connection? In the UM2435 user manual stm32wb are some power related schematics. The 5v has a 10uf +100nf and the 3v3 has 1uf and few 100nf....

My hardware knowledge is not good enough to determine the size I need, please help.

Kind regards,

Taxara

[Taxara]

So i've found out that the pol capacitor didnt work for every system... I continued the research and found the issue, during a certain state there is a huge interference on the 3v3 supply due to other system hardware. The interference reached voltages >4v for a few ns. This is too mutch (3.6v is set as max for STM32WB55) the ble core lost connection but the mcu core didn't seem to mind and more or less continued its normal behavior. Perhaps the ble core did continue as well but just being out of sync, I do not know for sure.

I've reduced the interference by adding a low pass filter on the supply going to the devboard and now everything is working as expected.