ADS8568: Can the REFP pins be driven directly

Amy Luo

Part Number: ADS8568

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

over 3 years ago

0 Dale Li over 3 years ago

TI__Mastermind 40815 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

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ADS8568: Can the REFP pins be driven directly