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ADS124S08: internal gain & offset error equal for each channel

KKF
Expert 4455 points
Part Number: ADS124S08


Hi TI ADC team,
Is my assumption correct, that ADS124S0x gain & offset error are independent of the ADC input channel that is selected? It is important for customer to know for calibration. PGA gain setting will not be changed in customer application.
Or can the gain / offset error change with channel selection? 


The variation of the Ron of the internal MUX is neglibigle for system accuracy even when the PGA is bypassed, right?

Thanks & BR,
KF

  • 0
    TI__Guru** 113765 points

    Hi KKF,

    Offset error is primarily a part of the PGA and modulator stages.  Issuing the SFOCAL (internal self-offset calibration) will apply an internal short and correct the offset error to within the level of noise with respect to the data rate and PGA gain selected.  Using the Global Chop feature can minimize the errors at the expense of additional conversion time to complete the chopping sequence.

    Gain error can be related to the PGA or the reference source.  However, the ADC is factory trimmed for the various gain settings to within the specifications of the datasheet.

    The effect of the mux will be negligible as compared to any input filter resistance within the input path.  As the internal short for using the SFOCAL self-offset calibration also uses the mux, the variation or potential change of the mux will only be impacted to the level of noise or less.  In other words not measurable.

    In very general terms, the only calibration that is required is the self-offset calibration (unless Global Chop is used).  Depending on the sensor and measurement type additional calibration may be necessary, but usually this is done in software due to error in the sensor itself such as load cells, RTDs, thermocouples, pressure sensors, etc..

    Best regards,

    Bob B