VBAT connection

I understand that VBAT is used to keep a 4K of RAM and the RTC going in case of main power failure.

What would I connect it to if I don’t care for that feature? 3.3V or leave it floating? Eagle gives an error about No SUPPLY for POWER pin U$4 VBAT if I don’t connect it to anything.


I think to remember that datasheets suggest to connect to 3V3.

I’m not sure that VBAT will keep 4K powered tho’ - It sounds a bit big.

Leave it floating if you are not using it

@kennethlimcp, @waspinator, the STM32F20x ref. manual, 4.1.2 Battery backup domain, says:

If no external battery is used in the application, it is recommended to connect the VBAT pin to
VDD with a 100 nF external decoupling ceramic capacitor in parallel.



Oh yes i wanted to say that but couldn’t find in the manual. Thanks!