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Original question:

How much GAIN ERROR performance can be improved of ADS8568 if we used an external reference - REF5025?

ADS8568: Can the REFP pins be driven directly

Amy Luo
Expert 6895 points
Part Number: ADS8568
Other Parts Discussed in Thread: REF5025

Hi team,

One of our customers wants to improve the temperature drift performance of the ADS8568. The ADS8568 internal reference voltage drift is ±10ppm/℃. Gain error drift is ±6ppm/℃. Based on the analysis in the link post below, using an external high-precision reference, directly drive the REFAP, REFCP, REFDP pins, the gain error of the internal buffer can be eliminated.

https://e2e.ti.com/support/data-converters/f/data-converters-forum/551657/how-much-gain-error-performance-can-be-improved-of-ads8568-if-we-used-an-external-reference---ref5025?tisearch=e2e-sitesearch&keymatch=ads8568#

By the same token, this should also eliminate the gain error drift of the internal buffer. My question is whether the REFAP, REFBP, REFCP and REFDP pins can be driven directly, and whether the outside need to add a buffer with a low offset voltage?

Best Regards,

Amy 

  • 0
    TI__Mastermind 38125 points

    Hi Amy,

    Either internal or external reference buffer is still needed to settle the signal because ADS8568 is a switched-capacitor input SAR ADC. Using a low drift external voltage reference with internal buffer is a good solution. For example, REF5025 that has 2.5ppm/C typ and 3ppm/C max vs. 10ppm typ no max on ADS8568's internal reference.

    Also, low drift components including resistors in the signal chain should be selected if the drift performance is a concern.

    Best regards,

    Dale