Hall current sensor is a excellent choice design for negative current sensing. Designer can directly series the hall current sensor with negative power supply since hall current sensor in general is a galvanically isolated and capable of monitor DC or AC current. TI design and produce more than ten high performance hall current sensors to meet most industry applications. TMCS1108 is a galvanically isolated Hall-effect current sensor capable of DC or AC current measurement with high accuracy, excellent linearity, temperature stability, low cost and small package. the 0 approximately 20A input current range with 80kHz bandwidth with four sensitivity options (50mV/A, 100mV/A, 200mV/A, and 400mV/A) can meet lots of applications. the typical circuit shown in Figure 3-1. The circuit is quite simple and straightforward.

Figure 3-1 Current Sensing for Negative Power Supply Based Hall Current Sensor

The function between input current and output voltage as formula 1 shows. Here, Vo is output voltage of hall current sensor, I_L is load current, and G is gain of hall current sensor.

One drawback for hall current sensor is that there is error of input offset current. This can potentially introduce some errors in some conditions especially the input current less than 100mA.