TIDA-01421: Peripheral RC Values Calculation

The resistor (R) and capacitor (C) values will depend on the characteristics of the motor current ripple signal.  The goal of this circuit is to amplify only the frequency of the ripple signal, and attenuate the low-frequency (DC) and high-frequency (noise) content.  The op amp stages form a bandpass filter (blocks low-frequency and high-frequency) with passband centered on ripple fundamental frequency.  The comparator stage compares the output of the op amps to a voltage threshold, producing a pulse stream.  Ideally there is one pulse for each ripple cycle, allowing a simple pulse-counting function to keep track of motion.  A reference for filter design is https://webench.ti.com/filter-design-tool/filter-type .