Hello Rolek, Based upon your questions, I think you are asking for a fully differential input, which the ADS8166 does not support. You still keep the same full scale analog input range with either single-ended or pseudo-differential (AINP ranges from 0V to Vref in both cases), but the AINM level can be near GND and ~1/2Vref. You are correct, in 'Single ended', AINM must be in the range of +/-0.1V, and 'Pseudo-diff', AINM (using the internal REF) must be in the range of 1.948V to 2.148V. If you exceed this range for AINM, then the data sheet specs will degrade. If you stay within this range, then you will meet datasheet performance over the full temperature range and data rates. Since there is a 'negative' input, you can reject small common mode variations around these two fixed levels (GND or 1/2Vref). However, if you have a differential input voltage of 1V, for example, with AINP=4V and AINM=3V, you will not get data sheet performance. I hope this helps clear things up. Regards, Keith N. Precision ADC Applications
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