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Using the IR217x Linear Current Sensing ICs

Using the IR217x Linear Current Sensing ICs

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.