Patent ID: 6574062
Filing Date: 2003-06-03
Classification: G11B

Abstract:
A disk drive comprising:(a) a disk; (b) a head; (c) a voice coil motor (VCM) for actuating the head radially over the disk, the VCM having a voltage control input; (d) a spindle motor for rotating the disk, the spindle motor comprising a plurality of windings and a rotor rotatable at a variable spin rate wherein the rotor generates a back EMF (BEMF) voltage across the windings proportional to the spin rate of the rotor; (e) a plurality of switching elements coupled to the windings; (f) switch control logic for generating switch control signals applied to the switching elements for commutating the spindle motor during normal operation and for generating an internal supply voltage from the BEMF during a spin down mode, the internal supply voltage applied to the voltage control input of the VCM for parking the head; (g) a demand limit circuit for disconnecting the internal supply voltage from the voltage control input of the VCM when the internal supply voltage falls below a predetermined level, and for reconnecting the internal supply voltage to the voltage control input of the VCM once the internal supply voltage recharges to a predetermined level, thereby enhancing power management during the spin down mode.