15.4.14.1.1 Error Compensation Coefficient Calculation
To calculate the ADC gain error compensation coefficient, two reference voltages are required. The ADC has one input connected to 15/16 of AVDD voltage. When it is assumed that the ADC offset after calibration is zero Equation 15-2 can be used to calculate the compensation coefficient.
The offset may not always be calibrated to exact zero. Refer to the ADC electrical specifications for more information.
If the application requires more precise gain error compensation the second data point is needed. The external resistor voltage divider can be added to provide the second reference voltage on one of the ADC analog inputs. The second reference voltage can be 2%-10% of AVDD. If the external resistor divider voltage is AVDD/16, then the two reference voltages’ gain error compensation coefficient and offset error can be calculated as shown in Equation 15-3.