Skip to main content
Explorer II
October 2, 2025
Solved

RTC_OUT availability while STM32H7 is powered off

  • October 2, 2025
  • 1 reply
  • 952 views

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

    This topic has been closed for replies.
    Best answer by mƎALLEm

    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. 

    1 reply

    mƎALLEmAnswer
    Technical Moderator
    October 2, 2025

    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. 

    AndreaTWAuthor
    Explorer II
    October 2, 2025

    Thank you so much

    Technical Moderator
    October 2, 2025

    Sorry,

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

    I've already fixed it.