This section will cover the basic operation of the current sense IC. These Linear Current Sensing ICs are designed to transfer current sense information from the high side part of a Motor drive circuit to the low side circuit, so that the information may be processed by the ground referenced control circuits.
The Analog input signal is actually a voltage which comes from the voltage drop across an external sensing resistor. The sensing resistor senses the motor phase current, and generates a small AC voltage signal input to the IR2175 Current sensing IC. The maximum input signal is +260 mV so the sense resistor should be chosen such that the desired setting for over current would generate 26 0mV across it.
The AC input signal is converted to a PWM signal, in the high side circuitry of the IR2175, using a carrier frequency of 130 kHz. The PWM signal is then level shifted down to the low side ground referenced circuit.
