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ADS1209: Gain error and reference voltage.

Ole
Prodigy 20 points
Part Number: ADS1209

Hi

When looking at the datasheet for the ADS1209 i am in doubt how to understand the Gain error and the Gain error thermal drift parameters (G­ERR and TCGERR).

For the gain error, "Gerr" it says "Referenced to Vrefin", for the thermal drift "TCGerr" it does not say that.

The question is whether both these parameters include the drift and error of the internal voltage reference or not?

Best regards

Ole

  • 0
    TI__Guru**** 168605 points

    Hi Ole!

    Welcome to our e2e forum!  The 'TC' errors in the ADS1209 datasheet are the temperature coefficient dependencies, so the "TCGerr" is just the typical Gerr expressed in PPM/`C.  It does include the reference voltage errors.  Feel free to post additional questions as they come up! 

  • 0 in reply to Tom Hendrick
    Prodigy 20 points

    Hi Tom

    Thank you for your answer.

    I just wonder, if the Gain Error parameters include the errors of the internal reference why are the errors of the reference then much bigger than the Gain Errors stated?

    e.g.

    Gerr :          max 0.5% FSR                    compared to           Vrefout: max 2.550V coresponding to (0.050 / 2.500)*100 = 2%

    TCGerr:      typical +/-1.3 ppm/degC    compared to           TCVrefout: typical +/-20 ppm/degC

    What I actually need to know is the max and min Gerr and TCGerr, when using an ideal external reference?

    Best regards

    Ole

  • 0 in reply to Ole
    TI__Guru**** 168605 points

    Hi Ole,

    Sorry for the delay here, I missed your comment yesterday.  The initial error of the internal reference can be the +/-2% you noted above.  And since the gain is set by the reference and FSR is +/-Vref, the Gerr and TCGerr from the datasheet is still valid.  During system calibration, if you assumed an ideal internal reference of 2.5V, you would potentially see higher gain error.