RTC_OUT availability while STM32H7 is powered off

AndreaTW · ‎2025-10-02

Hi,
I'm using an STM32H7 microcontroller and need to get the RTC working.
I set RTC_OUT to 1Hz and set the LSE to a 32.768Hz crystal, and inserted the CR2032 battery.
When the microcontroller is powered (VDD 3V3), I see the waveform oscillating at a frequency of 1Hz.
My question is: should the signal on the RTC_OUT pin remain when I remove the power?
Thanks

mƎALLEm · ‎2025-10-02

Hello,

Indeed RTC_OUT still alive and it remains active when the main power (VDD) is removed and only the backup battery VBAT is present. This is because the RTC and its associated functions, including RTC_OUT, are powered by the VBAT domain in such scenario.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

View solution in original post

mƎALLEm · ‎2025-10-02

Hello,

Indeed RTC_OUT still alive and it remains active when the main power (VDD) is removed and only the backup battery VBAT is present. This is because the RTC and its associated functions, including RTC_OUT, are powered by the VBAT domain in such scenario.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

AndreaTW · ‎2025-10-02

Thank you so much

mƎALLEm · ‎2025-10-02

Sorry,

But you need to accept the post that answered your question and not your confirmation ;).

I've already fixed it.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.