20.2 Overview

The Brown-out Detector (BOD) monitors the power supply and compares the supply voltage with the programmable brown-out threshold level. The brown-out threshold level defines when to generate a System Reset. The Voltage Level Monitor (VLM) monitors the power supply and compares it to a threshold higher than the BOD threshold. The VLM can then generate an interrupt as an “early warning” when the supply voltage is approaching the BOD threshold. The VLM threshold level is expressed as a percentage above the BOD threshold level.

The BOD is controlled mainly by fuses and has to be enabled by the user. The mode used in Standby sleep mode and Power-Down sleep mode can be altered in normal program execution. The VLM is controlled by I/O registers as well.

When activated, the BOD can operate in Enabled mode, where the BOD is continuously active, or in Sampled mode, where the BOD is activated briefly at a given period to check the supply voltage level.