stm32g030f6 rtc vdd/vdda no vbat

[JCuna.1]

Hi, I am planning to use stm32g030f6 and also use RTC peripheral with super cap to keep date. However, this IC does not have VBAT pin. Reading datasheet said, that RTC domain can also be supplied from VDD/VDDA pin, but this means that when a voltage supply interrupt, the mcu will not detect and it will start using super cap energy from VDD/VDDA pin, so, the purpose to target only rtc supply energy with super cap is compromised.

Could you clarify if my assumption is correct, and how to achieve my design (super cap supplying energy to rtc when main voltage is down)?

[Peter BENSCH · Accepted solution]

The data sheet not only mentions that VBAT is bonded to VDD/VDDA in package variants without a dedicated pin. For an independent supply of the VBAT domain incl. RTC, however, a separate pin is absolutely necessary. Conversely, this means that you cannot use a package TSSOP20 and must use the LQFP48 (or another STM32) if the RTC is to be supplied independently.

Does this answer your question?

Regards
/Peter

[Issamos]

Hello @JCuna.1 

I confirm your proposition and I suggest you to use another MCU such as the STM32G030CxT if you want to have an independent power source for the RTC.

Best regards.

II