Circuit and method for modulating the commutation frequency of a disc drive motor

摘要

A motor control circuit controls a motor in a disc drive. The motor control circuit includes a voltage controlled oscillator (VCO) providing a commutation timing signal. A commutation circuit is operably coupled to the VCO and provides commutation signals to the motor based on the commutation timing signal. A phase locked feedback circuit is operably coupled to the commutation circuit and provides a feedback signal to the VCO based on a sensed commutation phase to control a frequency of the commutation timing signal. A modulator is operably coupled to the phase locked feedback circuit and modulates the feedback signal. A method is also provided in which the commutation timing signal is modulated so as to spread a frequency spectrum of the commutation signals.