Patent ID: 6493169
Filing Date: 2002-12-10
Classification: G11B

Abstract:
A disk drive that incidentally generates undesirable acoustic noise during an operation mode, the disk drive comprising:a spindle motor having a plurality of windings and a rotor rotatable at an operating spin-rate during the operation mode of the disk drive; switching elements; a commutation state sequencer including a sequence of commutation states for generating a sequence of control signals, the sequence of commutation states including a present commutation state and a next commutation state; the switching elements being responsive to the sequence of control signals for sequentially applying a voltage across a selected combination of the windings to generate a torque on the rotor in order to maintain the operating spin-rate; a spindle motor control system for providing a series of commutation clock pulses to advance the commutation state sequencer from the present commutation state to the next commutation state, the series of commutation clock pulses having a corresponding series of commutation clock periods, at least two of the commutation clock periods each having a systematically introduced variation from a nominal commutation clock period that depends on the operating spin-rate; and whereby the systematically introduced variation for each of the at least two commutation clock periods reduces the acoustic noise in the disk drive.