Abstract: A disk drive has a microprocessor, a digital controller chip, and an analog power chip, and a multi-winding spindle motor. The power chip operates under gross and fine control to connect and disconnect, during ON and OFF phases, a supply voltage to each winding on a PWM basis. The magnitude of the supply voltage and the temperature of the power chip vary. The microprocessor sends a digital control signal to the controller chip for gross control. The controller chip sends a PWM signal to the power chip for fine control. The power chip has pins for receiving the supply voltage, for sending a modulated signal to the controller chip; and for receiving the PWM signal from the controller chip.

Abstract: An automatic head retract system for a disk drive. The system operates in response to electric power turn off to retract the heads to a landing zone on the disk surface. The heads are retracted by operating a positioner motor under the control of logic internal to the disk drive unit without intervention by a host computer. The positioner motor comprises a multiphase DC brushless motor which, after power loss, is supplied with current from a capacitor charged during normal drive usage, and by the back EMF of a spindle motor. A latch mechanically locks the heads in the landing zone.

Abstract: An automatic head retract system for a disk drive is disclosed which operates in response to electric power turn off to retract the heads to a landing zone on the disk surface. The heads are retracted by operating a positioner motor under the control of logic internal to the disk drive unit without intervention by a host computer. The positioner motor comprises a multiphase DC brushless motor which, after power loss, is supplied with current from a capacitor charged during normal drive usage and by the back EMF of a spindle motor. A latch mechanically locks the heads in the landing zone.

Abstract: A low cost disk drive system includes track zero information located in a single sector on the disk surface. The information is comprised of a first type of signal located in tracks to one side of an arbitrary reference track and a second type of signal located in the tracks to the other side of the arbitrary reference track. The magnetic head of the disk drive system is moved radially with respect to the disk and the transition between the signals detected in order to locate the head at the reference track.

Abstract: Disclosed is a rotational speed control system for comparing the rotational speed of a rotating disk as indicated by index pulses occurring one or more times per revolution of the disk, with a reference time representing the desired time between successive index pulses. The system employs logic circuitry external to any microprocessor control system employed by the rotating disk system. The reference time may be supplied by counters counting externally supplied clock pulses to a fixed value. The speed control system provides a speed up command or slow down command in a manner proportional to the speed error to the disk drive motor where the time between successive index pulses is greater or less, respectively, than the reference time.