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Original question:

ADS1018-Q1: ADS1018 Datasheet Accuracy Deviation Maximum Value

ADS1018: Gain error missmatching

user5250576
Prodigy 40 points
Part Number: ADS1018
Dear TI,

I have found some mismatching in the given gain error and its typical characteristic. In Chapter 7.5 the typical gain error is 0.05% at 25°C but on Figure 6 the 2.048V curve has much lower gain error (0.005%) at +25°C.
Note 3 in chapter 7.5 says gain error includes all errors from onboard PGA and voltage reference. Could you please include these PGA and offset errors into the curves on Figure 6 too, if this is the reason of the difference?

Thank you in advance!

Peter
  • 0
    TI__Guru* 97795 points

    Peter,


    Thanks for your comment on the gain error. I believe that figure 6 is trying to show the relative gain error between the different FSR settings over temperature. If you look at the curves, you can see they have the same basic trend over temperature, without much difference between the different FSR. It's possible for this curve the gain error was normalized to the ±2.048V FSR at 25C. However, the gain error typical and maximum are listed in the Electrical Characterisitcs table on page 6, which should be the values used to design your system.

    The gain error only includes the gain error of the ADC and the error of the internal reference combined. With an internal reference that can't be measured externally, ADC gain error and reference error cannot be separated. It does not include the offset of the ADC.

    Joseph Wu