Connecting an External Battery to Vbat Pin of STM32F429I-DISC1

[onurkaanozkan]

Hi everyone,

I want to use my evaluation board's RTC Backup Registers to store some info when not powered. In order to do that i want to connect an CR2032 battery to the Vbat pin of the controller. Below is the part of the schematics of the board showing Vbat connections. Do i need to dismount R52 and connect the battery positive directly to Vbat there and battery negative to GND? Is this operation sufficient for my purpose? Thanks in advance... 

[Peter BENSCH · Accepted solution]

Welcome @onurkaanozkan, to the community!

The STM32F429I-DISC1 is one of the few where VBAT is not connected directly to VDD, so you can in fact remove R52 and connect a CR2032 directly to VBAT and its negative terminal to GND instead. This is completely sufficient, just make sure that the battery voltage of any other battery used does not exceed the permissible values specified in the data sheet.

Hope that helps?

Regards
/Peter

[onurkaanozkan]

Glad to be here Peter and thank you for your quick reply.

As far as i understand switching between Vbat and Vdd according to the presence of Vdd is managed inside the controller itself automatically. So when i power off my board(by unplugging the Micro-USB cable in my case) RTC backup registers will be powered by Vbat without any other action needed, am i right?

[Peter BENSCH]

Correct.