38.6.3.2 Rail-to-Rail Operation

The accuracy of the ADC is highest when the input common mode voltage (V_CMIN) is close to V_REF/2. To enable a full range of common mode voltages (rail-to-rail operation), the Rail-to-Rail bit in the Control C register (CTRLC.R2R) should be written to one. Rail-to-rail operation requires a sampling period of four cycles. This is achieved by enabling offset compensation (SAMPCTRL.OFFCOMP = 1). Rail-to-rail operation should not be used when offset compensation is disabled.