8.3 Current Sense Amplifier Signal Filtering

For high current MC applications, it is required to use a small current sense shunt and a low gain for CSA, in order to match the output signal with the MCU's ADC range.

Due to the CSA's large bandwidth, the sharp parasitic current spikes induced by the external MOSFET bridge commutation can cause the output to be clamped at the rail limits and affect the motor control processing. A filtering method for the signal can be implemented (see CSA Filtering Circuit).

For high efficiency, the filter components should be placed near the CSA inputs. In order to not affect the differential gain and the initial settled offset, the input resistor should stay as low as possible (4.7-10Ω). The filter component selection is based on a 20 kHz PWM frequency.