Clash in reference voltage selection on AD7617

[jonnew]

To use internal reference REFSEL should be pulled high. However REF pin is driven by external reference. REFSEL should be pulled low.

[jonnew]

Even with a bodge to connect REFSEL to DGND, there is a -0.9V offset on grounded analog inputs.

Im not sure what the cause of this is

[jonnew]

Can we try removing R59 to just use the internal reference?

[jonnew]

So far, I have done one set of modifications that has solved this issue

1. Replace AD1617 with AD1616 (16-bit version that i was original using before chip shortage)
2. Remove R63 and bodge REFSEL to DGND

This seems to result in perfectly normal +/-10V IO with good linearity and matching between input and output. However, so fare this is all in the context of a bit file with an ILA in it. Im begining to worry that aside form this referencing issue, there might be some timing issue as well. I have no idea why (1) helped anything since I cannot find a reason why the 14-bit version of the chip would have this effect. The only difference I can see is that the 2 LSBs are zeroed.