Using an oscillator for LSE in battery mode?

[Lars Beiderbecke]

Suppose I use an oscillator instead of the suggested resonator for LSE. Will that even work, i.e., will the internal RTC continue to function when in battery mode? I assume that I'd have to power both oszillator and STM32 (using Vbat)?

[waclawek.jan]

Which STM32?

Most probably yes. Don't forget that RCC_BDCR.LSEBYP has to be set. There are mixed reports on whether RCC_BDCR.LSERDY is usable for that case; but that's not fatal.

JW

[Lars Beiderbecke]

Thanks, I think I will give it a try, but maybe on an old board I have.