Patent ID: 6970319

Claim:
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 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 voltage during a spin-down mode, the internal supply voltage applied to the control input of the VCM for parking the head; and (g) a demand limit circuit for controlling the amount of current drawn by the VCM from the internal supply voltage while parking the head, the demand limit circuit comprising: a comparator for comparing the internal supply voltage to a threshold to activate a demand limit control signal; and a signal generator for generating a periodic signal for periodically disconnecting the internal supply voltage from the control input of the VCM while the demand limit control signal is active.