What is common mode voltage exactly in current sense amplifier ? how to select a current sense amplifier based on common mode voltage?
For an amplifier, the input common mode voltage range is the range of inputs across which the amplifier will operate as advertised in the datasheet.

It is also important not to exceed the absolute maximum ratings.

Exceeding the common mode range means that the amplifier will not meet it's datasheet specifications and can have very odd effects such as output phase reversal (common in older JFET input amplifiers).

Some devices specify what will happen when operated outside the common mode range, but most do not; for a high side current sense amplifier that is powered from the same supply as being sensed requires a common mode range that goes to the positive power rail.

The AD8207 is specifically designed for this type of application; the common mode range exceeds the power rails (both positive and negative) by a significant margin, so you can use this device in your application if you power it from 5V; the maximum common mode continuous when powered from 3.3V is only 35V for proper operation which is lower than your application is sensing.



Trying to use this device to sense beyond 35V when powered from 3.3V will not damage the device (according to the absolute maximum ratings) but the operation of the part is not guaranteed.