High Side Current Sensing for High Side Switching

Sometimes, there are unexpected solenoid and excessive corrosion occurs on current sense circuit. Corrosive effects can be occurred because of the differential voltage between the ground and the load. To reduce that possibility, the shunt and the switch are placed on the high side. When switch is off, the battery is removed from the load, it will avoid damage from potential shorts to ground. However, the recirculating current measurement and diagnostic still allowed. Here is the schematic diagram of the circuit:

When the switch is on, the common-mode voltage increases the battery voltage because the battery voltage is connected to the load. When the switch is off, the common-mode voltage drop below the ground because of the voltage reversal that across the solenoid. [Circuit’s schematic diagram source: Analog Application Note]