16.6.8 3.3V Brown-Out Detector Operation
The 3.3V BOD monitors the 3.3V VDDANA supply (BOD33). It supports continuous or sampling modes.
The threshold value action (reset the device or generate an interrupt), the Hysteresis configuration, as well as the enable/disable settings are loaded from Flash User Calibration at startup, and can be overridden by writing to the corresponding BOD33 register bit groups.