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ADS4149 DC offset correction

David Price1
Prodigy 20 points
Other Parts Discussed in Thread: ADS4149

I am looking to use the DC offset correction function of the ADS4149 converter.

I note that the converter has a 'FREEZE OFFSET CORRECTION' control which I would assume I apply after the time defined by the 'TIME CONSTANT' has been reached, however I am unclear on what to expect if I don't apply the freeze control.

I am thinking DC offset may be a function of temperature and that if I leave the correcection 'unfrozen' will it continue to remove any offset or will I have to reapply the function again ?

  • 0
    TI__Genius 17340 points

    Hi David,

    I've sent a request to our design team. I was unable to capture the results when enabling and disabling the freeze offset control with my capture card.

    Regards,
    Matt Guibord 

  • 0
    TI__Genius 17340 points

    Hi David,

    Sorry for the delay. When offset correction is used and "Freeze offset correction" is not enabled, then the part WILL continue to correct for changes in offset due to temperature drift or otherwise. When you freeze the correction, the last "correction value" is held. Upon unfreezing the correction, the correction will resume. I need to verify that the correction does not restart when correction is unfrozen and rather it starts from where it left off.

    One way to use the freezing feature is in the case of measuring low frequency components. First, the offset can be calibrated out without a signal applied, then the value can be frozen. You're then able to measure low frequencies without the offset correction affecting the measurement. After a certain time period or a known change in temperature, the offset correction can be unfrozen to compensate for the drift.

    The total range of offset correction is limited to about +/- 16 mV, which is enough to cancel the ADC offset over all operating conditions.

    Regards,
    Matt Guibord