SDAA132 December 2025 MSPM33C321A
To use any of the peripherals in the low frequency subsytem (LFSS) the VBAT pin must be powered by an external voltage. This can be VDD or another power supply.
TI recommends connecting a 1μf decoupling capacitor to the VBAT pin (see VBAT Decoupling Circuit). Higher-value capacitors can be used but can impact supply rail ramp-up time. Decoupling capacitors must be placed as close as possible to the pins that to decouple (within a few millimeters).