Hi
I have a comparator that will be supplied by Vdd=3.3V and Vss connected to GND, in the datasheet it is written that the common-mode input voltage maximum value is Vdd-1.5V, does that mean that the average of the inputs needs to be less than Vdd-1.5 or both of them? If I guarantee that the average of the inputs is less than Vdd-1.5 can the positive input be greater than Vdd, 4V for example?

 

The common mode input voltage specifies the range that both inputs must stay between at all times for correct operation. With Vdd=3.3V, 4V is not allowed.

 

The comparator does not care about the average of the two inputs. The limits apply to each input individually.