Patent ID: 8189284

Claim:
An apparatus for driving a voice coil motor (VCM), the apparatus comprising: an error circuit that receives a target back electromotive force (bemf) and that generates an error signal; a current determination circuit that is coupled to the error circuit; a driver that is coupled to the current determination circuit and that is configured to be coupled to the VCM; a mode selection circuit that is coupled to current determination circuit and the driver and that receives a threshold signal, wherein the mode selection circuit selects a normal mode when the output of the current determination circuit is less than the threshold signal and a silent mode when the output of the current determination circuit is greater than the threshold signal, and wherein the mode selection circuit provides at least one first pulse having a first width to the driver during the normal mode, and wherein the mode selection circuit alternately provides at least one second pulse having a second width and at least one third pulse having the first width, and wherein the second width is greater that the first width; a sampling circuit that is coupled to the driver, the mode selection circuit, and the error circuit, wherein the sampling circuit provides a measured bemf to the error circuit following the first and third pulses; and a silent mode compensation circuit that is configured to be coupled to the VCM and that is coupled to the error circuit, wherein silent mode circuit generates an estimated bemf following the second pulse.