Patent ID: 6954324
Filing Date: 2005-10-11
Classification: G11B

Abstract:
1. A disk drive comprising: (a) a disk comprising a plurality of tracks, wherein each track comprises a plurality of data sectors and a plurality of servo wedges; (b) a head actuated over the disk; (c) a spindle motor for rotating the disk at an operating speed in response to a spindle control current, the spindle motor comprising a plurality of windings which generate a back electromotive force (BEMF) voltage; (d) a BEMF detector for generating a BEMF signal by comparing the BEMF voltage to a threshold; (e) a current modulator for generating a PWM signal representing the spindle control current; (f) BEMF detection window circuitry for periodically disabling the PWM signal for a predetermined interval to attenuate noise in the BEMF voltage while the BEMF detector compares the BEMF voltage to the threshold; and (g) a disk controller for: