Patent ID: 6850384

Claim:
A disk drive comprising: (a) a disk; (b) an actuator arm; (c) a head connected to a distal end of the actuator arm; (d) a voice coil motor (VCM) comprising a voice coil, the VCM for rotating the actuator arm about a pivot to actuate the head radially over the disk; and (e) a VCM driver comprising: an H-bridge driver comprising a plurality of driver switches for driving current from a supply voltage through the voice coil to ground; a first sense resistor connected in series between the supply voltage and at least one of the driver switches; a first amplifier for amplifying a voltage across the first sense resistor to generate a first sense signal; a second sense resistor connected in series between at least one of the driver switches and ground; a second amplifier for amplifying a voltage across the second sense resistor to generate a second sense signal; a first oscillator for generating a first frequency signal in response to the first sense signal; a second oscillator for generating a second frequency signal in response to the second sense signal; and a first counter responsive to a reference frequency, the first frequency signal, and the second frequency signal, wherein an output of the first counter represents a current flowing through the voice coil.