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about ADC precision

Vera Mao
Expert 5065 points

hi dear supporting team,

If we need calculate the max error of an precision ADC,  could we use this formula?

TUE = sqrt (sq(Offset Error) + sq(Gain Error) + sq(DNL) + sq(INL))

but I think the gain error may be already included in INL, will this calculation double count the same factor? tks a lot!

  • 0
    TI__Guru 64775 points

    Hello,

    These terms will capture the primary sources of DC input error in an ADC.  These errors are typically measured with an ideal reference voltage so the reference voltage inaccuracy should also be included in your final calculations.

    There is a lot of really great information on ADC error calculations that also include the AC performance specifications in addition to the DC specifications.  Please take a look at the TI Precision Labs videos for more information.

    https://training.ti.com/ti-precision-labs-adcs

    Here are the videos sections on error and noise:

    https://training.ti.com/ti-precision-labs-adcs#section-3

  • 0 in reply to Collin Wells
    TI__Expert 5065 points

    Hi Collin,

    thanks for reply!

    understand that those factors are only for DC, because customer's application is close to DC, and they want to nail down a threshold for the system testing, so need figure out what's the max error could be.  so they are asking whether they could use this formula to calculate?  (this formula is from SLAA587)

    TUE = sqrt (sq(Offset Error) + sq(Gain Error) + sq(DNL) + sq(INL))

    I have went through those videos, there is no direct formula for calculate the error with INL,DNL, GAIN ERRor AND offset error. 

    if considering 3/6sigma distribution, for calculating the DC error, what's the formula should be? tks a lot!

  • 0 in reply to Vera Mao
    TI__Guru 64775 points

    Hello,

    Yes, your equation is correct for DC errors assuming an ideal reference voltage.  You can add the reference voltage error as a gain error to your equation and that will be complete.

    -Collin