Question:
In the analog Input specification of a differential ADC, what is the meaning of the common-mode input range?
Answer:
The input common voltage is the (Ain+ + Ain-) / 2. Depending upon ADC architecture, some ADCs have a limited common mode range where the typical value is Vref/2. Other architectures have a wider common mode voltage range that can vary all the way between AVss and AVdd. Violating the common voltage range can result in erroneous conversion results from the ADC.