Current sense IC with circuitry for eliminating ripple current error from motor current measurement

1. Field of the Invention A circuit for recovering a current sense signal which is offset by a common mode displacement, such is the case when the signal is the voltage across a current sense resistor located on the high side bus or between the switches of a motor controller circuit. The circuit of the present invention converts the voltage across the resistor into a pulse code modulated (PWM) data, then downshifts the voltage, such that the signal of interest may be processed and recovered at the lower voltage for current feedback control purposes. The conversion of the measured current into a PWM signal is performed such that the PWM signal is synchronous with the motor PWM frequency. Although the output of the IC is synchronous with the motor PWM frequency, the output duty cycle is completely independent of the motor PWM duty cycle. In this way, the reconstructed sampled output of the IC is exactly equal to the fundamental motor current, without the effect of ripple current.