Disk drive data synchronizer with window shift synthesis

Abstract

A phase-locked system for recovering data from a disk drive includes a phase detector for signalling the difference in phase between incoming delayed data pulses and a phase detection window clock signal. The phase detection window clock signal is derived from one output of a phase shifter driven by the output of a voltage-controlled oscillator whose frequency is controlled by the phase detector. The phase-locked loop is completed by comparing the phase detection window clock signal output of the phase shifter with the incoming delayed data pulses in the phase detector. Data detection window clock pulses, defining time windows in which the delayed data pulses are discerned, are produced at a second output of the phase shifter. The phase shifter produces a delay variable in precise increments over a wide range, causing a variable phase relationship between the time windows and the delayed data pulses that are to be discerned therein.