Quentin, Thanks for the basic schematic. There is one thing that I noticed that might be causing a problem. For the ADS1246 , the reference input is limited to (AVDD-AVSS)-1. That means if you're using a 3V supply, then you should use a maximum voltage of 2V. The specification is listed in the max column of the Recommended Operating Conditions on page 8 of the datasheet. I believe that this limitation is due to the input capacitive sampling charge and discharge of the ADC modulator. During the sampling, charge may be lost with larger references, causing an error. I don't think there's a good workaround for this problem. You might try to run the AVDD from the other 3.3V supply and try to drive the sensor from a lower voltage. Alternately you might be able to do a voltage divider from the 3.0V supply to drive the reference. Joseph Wu
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