8.4.1 VDDBU Power Architecture

The backup power switch aims at optimizing the power consumption on VDDBU source by switching the supply of the backup digital part (BUREG memories + 64 kHz RC oscillator) to VDDANA.

When enabled, the backup power source can be automatically switched to VDDANA, which reduces power consumption on VDDBU. Then, VDDBU powers the pads, VDDBU POR, and the 32 kHz crystal.

The power source (VDDANA or VDDBU) can be selected manually or can be set to work automatically by programming an SFRBU register (refer to SFRBU_PSWBUCTRL in the section Special Function Registers Backup (SFRBU)).