JAJSGG2C October 2018 – June 2019 ADS125H02
Auto-zero mode is a continuous calibration technique that provides low offset voltage and near-zero drift over time and temperature. Auto-zero mode is a form of chopping that covers the internal ADC signal chain. The ADC alternates the polarity of consecutive conversions by internally reversing the input signal. The digital filter subtracts the results of two reverse-polarity conversions to yield the final conversion data. The subtraction result removes the offset error. Auto-zero mode is available only for use with the AIN0 and AIN1 inputs. See the MODE1 register for details on how to program auto-zero mode.
Auto-zero mode changes the data rate and the conversion latency time corresponding to the first conversion. The new data rate is equal to 1 divided by the latency values listed in Table 8. For example, when the ADC is programmed to 20 SPS and FIR mode, the new data rate is = 1 / 52.22 ms = 19.15 SPS. Regardless of the new data rate, the location of the digital filter frequency notches are unaltered. Thelatency time corresponding to the first conversion is equal to 2 × the latency time values listed in Table 8. Auto-zero mode reduces conversion noise by √2 because auto-zero mode effectively averages the data from two conversions.