The AVR Dx devices provide up to three Analog Comparators, each two of them configurable in Window mode. In Window mode, a voltage window can be defined, and the selected comparator indicates whether an input signal is within this range or not.
The devices are equipped with a voltage reference for Analog Comparators, selectable via the Voltage Reference (VREF) peripheral (the same value will apply to all ACs in the device). Each comparator is equipped with an additional 8-bit DAC that allows a fine adjusting of the voltage reference levels.
To improve noise immunity, the hysteresis feature is available using the HYSMODE[1:0] bit field in the ACn.CTRLA register. This feature has selectable levels and helps prevent constant toggling of the output when the noise-afflicted input signals are close to each other.