As alluded to earlier, not all high common mode voltages are unintentional. In this battery cell monitoring application, a high common mode voltage is necessary to measure the battery current in systems that can call for up to 36 V in some automotive sectors. The typical setup uses a current sense amplifier that measures the voltage drop across a small, known resistance and the difference can be used to calculate the current loading of the system as shown in Figure 3-7.

In this instance, one can see that the common mode voltage would be just under 36 V depending on the load current and is intentional to the design to operate with this high common mode voltage present. So, the multiplexer has to have nominal operation with a high common mode voltage for this application to work properly and a high voltage multiplexer would be the choice for this type of use case.