36.2.1.1 Self-Calibration

When OFCSEL = '10', the Self-Calibration sequence will be performed to adjust the input offset voltage. Self-Calibration allows software to periodically re-calibrate the input offset voltage, which may be useful in applications that operate over a wide voltage or temperature range.

The Self-Calibration sequence begins when OFCSEL = '10' and the Operational Amplifier Self-Calibration Start (OFCST) bit is set (OFCST = 1). During the Self-Calibration sequence, OPAxOUT is held in high-impedance (tri-state) mode, and all positive and negative inputs are connected to the V_DD / 2 voltage reference. Once the sequence is complete, the new input offset value is loaded into the OPAxOFFSET register, OPAxOUT is released from high-impedance mode, the positive and negative inputs are disconnected from the reference source, and module hardware clears the OFCST bit.

Important: The OFCSEL bits must be configured to select the Self-Calibration sequence (OFCSEL = '10') before the OFCST bit can be modified by user software.