Digital pulse width modulator with integrated test and control

Abstract

A pulse width modulator (PWM) circuit for generating pulses to enable a driver control unit to drive a pair of switching circuits for an electric motor including an input section for receiving an N bit digitized input signal to be modulated and a PWM counter for continuously counting up from zero to a predetermined number and back down to zero, the PWM counter generating a digitized triangular waveform having N bits of resolution corresponding to the predetermined number. A compare unit receives and compares the digitized input signal and the digitized triangular waveform to produce an output pulse and a dead-time generator unit produces a first pulse and a second pulse from the output pulse produced from the compare unit. The first and second pulses each drives a corresponding one of the switching circuits and the first and second pulses have different transition times relative to each other. A built-in test (BIT) circuit provides BIT input signals corresponding to the first and second pulses to verify correct operation of the PWM circuit including a feed back path from the driver control unit, the driver control unit having a higher level of integration than the PWM circuit, and the BIT input signals providing individual control of each of the PWM signals.