Patent ID: 6512470
Filing Date: 2003-01-28
Classification: G11B,H03L

Abstract:
A method of adjusting a frequency range of a voltage controlled oscillator in a data phase locked loop for reading data from an optical disk, the method comprising the steps of:a. providing a voltage controlled oscillator having a first input for receiving a first voltage signal corresponding to a frequency range of all output signal of the voltage controlled oscillator and a second input for receiving a second voltage corresponding, to an offset frequency value for adjusting a frequency of said output signal within said frequency range; b. providing a frequency/phase detector and coupling a first input thereof to a data signal output from an eight-to-fourteen modulation system of the optical disk, a second input of said frequency/phase detector being coupled to said output signal of said voltage controlled oscillator for comparison with said data signal; c. providing a loop filter having an input coupled to an output of said frequency/phase detector and an output of said loop filter being coupled to said second input of said voltage controlled oscillator for providing said second voltage signal thereto; d. providing an analog-to-digital converter having an input coupled to said output of said loop filter, said analog-to-digital converter providing a digital representation of said second voltage signal; and, e. providing a VCODAC generator having an output coupled to said first input of said voltage controlled oscillator to provide said first voltage signal thereto, said first voltage signal having a predetermined initial value corresponding to an approximate locking frequency of the data phase locked loop, said VCODAC generator having an input coupled to an output of said analog-to-digital converter for adjusting said first voltage signal at said output of said VCODAC generator responsive to variation of said second voltage signal.