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Nonlinearity Error

Jose Delgado
Prodigy 225 points
Other Parts Discussed in Thread: INA198

Hello,

Where can I find your equations in getting Nonlinearity Error?

 

Thanks for your response,

 

Jose D.

  • 0
    TI__Genius 14825 points

    Jose,

    Pages 6 and 7 of application note SLAA013 describe INL and DNL and how to calculate them.

  • 0 in reply to Jason Bridgmon
    Prodigy 225 points
    Jason,

    Sorry, I didn't mention the part that I am working on. It's the INA198.

    It has an analog input with an analog output.

    Thanks for your response,

    JD
  • 0 in reply to Jose Delgado
    TI__Genius 14825 points

    JD,

    Nonlinearity is defined as the deviation from a straight line on the plot of output vs input.  The magnitude of this error is: (Actual Output - Calculated Expected Output)/(Full scale range).

    Typically this test is performed at several discrete points from the low end to the high end of the range and the worst case error is reported.  the Calculated Expected Output in this case is defined as the Vsense Input Voltage times the Gain.

    Because we are not concerned with Gain or Offset errors at this time, we typically use an endpoint fit line between the most negative and most positive readings, and find the deviation of the measured output from that line.  There are times when a best fit line is used, which can be found with many different methods but the one I often chose is a least squares fit.

    There is an excellent book sponsored by TI: An Introduction to Mixed-Signal IC Test and Measurement by and Gordon W Roberts.  If you are interested in learning more about test and measurement of ICs, I encourage you to check it out.