Hello Hur, First, thanks for including the pictures, this helps with the question. In this case, although the analog inputs can range from -0.1V to 5.1V relative to AGND when AVDD=5V, the maximum measurable differential input range is +/-Vref, or (+Vref - (-Vref))=2VREFpp. With Vref=2.5V, this will be +/-2.5V, or 5Vpp. In your above drawing, you have +/-5V, or 10Vpp differential span, which will exceed for full scale input range by 2x. When driving the ADC inputs with a common mode voltage of 2.5V, AINP and AINN will range from 1.25V to 3.75V, 180deg out of phase of each other, for a full scale input signal. Although your THD performance may suffer, the wider AINP, AINN range allows AINN to be connected to 2.5V DC level (VREF), and then AINP can vary from 0V to 5V for a full scale differential input of +/-2.5V. I hope this helps clear things up! Regards, Keith N. Precision ADC Applications
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