SBASA57 September 2023 AMC131M01
PRODUCTION DATA
Certain signal chain errors can be corrected through a single room-temperature calibration. The AMC131M01 can store calibration values and uses the values to correct the results in real time. Among the errors that can be corrected in real time with the AMC131M01 are offset error and gain error.
Offset calibration is performed by determining the measured output of the signal chain when the input is zero voltage for a voltage measurement or zero current for a current measurement. The ADC conversion result for zero input can be measured and recorded in external nonvolatile memory. When the system is deployed, these values can be provided to the CH0_OCAL_MSB and CH0_OCAL_LSB registers. The AMC131M01 then subtracts these values from the conversion results prior to providing them to the host.
Similar to offset error correction, system gain error can be determined prior to deployment and can be used to correct the gain error in real time. Gain error is defined as the percentage difference in the ADC transfer function from the PGA gain corrected ideal value of 1. This error can be determined by measuring the results from both a maximum and minimum input signal, finding the difference between these results, and dividing by the difference between the ideal difference. Equation 11 describes how to calculate gain error.
To correct for gain error, divide each offset-corrected conversion result by the measured gain. The AMC131M01 multiplies each conversion result by the gain calibration factor stored in the CHn_GCAL_MSB and CHn_GCAL_LSB registers according to the method described in the Calibration Registers section. The host can program the measured inverted gain values into these registers to have them automatically corrected for each sample.