PURPOSE: To enable a VCO signal to be synchronized without generating phase fluctuation and step-out for readout data with frequency change and data omission by providing a frequency division means which n-frequency divides an output signal, and a switching means which selects either a frequency division output signal or a non-frequency division output signal.
CONSTITUTION: This circuit is comprised of a phase comparator 1, a time difference detection circuit 2, a loop filter 3, a voltage controlled oscillator(VCO) 4, a frequency division circuit 6, and a switching circuit 8. In a phase locking process. the switching means 8 selects a frequency output signal 18, and a phase locking operation is performed. At this time, reference pulse with that becomes the reference of phase comparison and time difference detecting operations is increased compared with a frequency division ratio, and phase difference detecting capacity can be expanded in proportion to the frequency division ratio, therefore, phase locking capacity can be also expanded in proportion to the frequency division ratio. In such a way, it is possible to synchronize the VCO output signal 11 with the readout data signal 10 without generating the phase fluctuation and the step-out for the readout data signal with the frequency change and the data omission.
NAGATA SHUNJI
IWAISHI KEISUKE
ISAKA KAZUO
HITACHI VIDEO ENG