The ADC incorporates offset and gain calibration commands, as well as user-offset and full-scale (gain) calibration registers to calibrate the ADC. The ADC calibration registers are 16 bits wide. Use calibration to correct internal ADC errors or overall system errors. Calibrate by sending calibration commands to the ADC, or by direct user calibration. In user calibration, the user calculates and writes the correction values to the calibration registers. The ADC performs self or system-offset calibration, or a system gain calibration. Perform offset calibration before system gain calibration. After power-on, wait for the power supplies and reference voltage to fully settle before calibrating.
As shown in Figure 81, the value of the offset calibration register is subtracted from the filter output and then multiplied by the full-scale register value divided by 4000h. The data are then clipped to a 16-bit value to provide the final output.
Calibration commands cannot be used when the device is in standby mode (when the START/SYNC pin is low, or when the STOP command is issued).