8.5.3 User Calibration

System calibration of the ADS1282-SP can be performed without using the calibration commands. This procedure requires the calibration values to be externally calculated and then written to the calibration registers. The steps for this procedure are:

1. Set the OFSCAL[2:0] register = 0h and GANCAL[2:0] = 400000h. These values set the offset and gain registers to 0 and 1, respectively.
2. Apply a zero differential input to the input of the system. Wait for the system to settle and then average n output readings. Higher numbers of averaged readings result in more consistent calibration. Write the averaged value to the OFC register.
3. Apply a differential positive or negative DC signal, or an AC signal, less than the full-scale input to the system. Wait for the system to settle and then average the n output readings.

The value written to the FSC registers is calculated by Equation 12.

DC signal calibration is shown in Equation 12. The expected output code is based on 31-bit output data.

Equation 12.

For AC signal calibration, use an RMS value of collected data (as shown in Equation 13).

Equation 13.