I am considering to use Nucleo-L432KC board and I need to use it's RTC with maintained time. User manual shows Vbat power in some internals of MCU but there is no pin to provide this power. Looks like the main chip's power source Vdd is the only source powering RTC block. Consequently Nucleo32 board with it also does not provide battery power for RTC backup even though it does have a crystal for RTC. Does this mean that RTC built in this MCU was not meant to be maintained in off-power mode and must be setup after every power-up or is there something I am missing?