29.3.2.1 Input Hysteresis
Applying an input hysteresis helps to prevent constant toggling of the output when the noise-afflicted input signals are close to each other.
The input hysteresis can either be disabled or have one of three levels. The hysteresis is configured by writing to the Hysteresis Mode Select (HYSMODE) bit field in the Control A (ACn.CTRLA) register.