STSPIN32G4 3.3V LDO disabled when VM is off
Good Day,
I've run into some issues with the power supply scheme for my custom board using a STSPIN32G4.
My design uses an external 5V switching regulator to power the internal 3.3V LDO, VM is switched on on-demand by signal from the MCU.
My observation is, that VM needs to be present in order for the internal 3.3V LDO to function, is that correct? This is not clear at all from the datasheet, as it looks like the LDO is completely independent. Upon investigation, I found section 5.1.2 which vaguely hints that my assumption is correct.
If that is indeed the case, this must be made more clear!
Additionally, this section hints, that even if the LDO is bypassed and the 3.3V externally supplied, turning VM on causes a device reset. Is this some inbuilt safety feature? Can this be turned off?
I’d be glad, if the datasheet could be a bit more precise about these topics. This is somewhat sad, because STM typically provides excellent datasheets.
Cheers,
D. Frejek