Daniel, I'm not sure that connecting the negative input to an external 2V reference would help you very much. It depends on the nature of your measurement. I wouldn't be a problem to make the connection, because the it is within the range of the operation for the negative input. However, you need to ensure that the current is there and you need enough resistance to keep that voltage 100mV above AVSS. If there is no current or the resistance is too low, then the voltage drops below 100mV and would be outside the range of the PGA. Additionally, you would be subject to error in the reference, so you might not be able to make an accurate measurement without some sort of calibration. Do you have a schematic you could share? There might be other alternatives to using an external reference. Joseph Wu
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