| 摘要 |
PURPOSE:To provide the phase locked loop in which an output signal frequency is not fluctuated by stopping the phase locking till an input signal comes after an input signal is interrupted. CONSTITUTION:The phase locked loop is provided with a voltage controlled oscillator 6, a phase comparator circuit 2 comparing a phase of an output signal CLK of the voltage controlled oscillator 6 with a phase of an input signal RD to provide a control voltage to the voltage controlled oscillator 6, and control circuits 10a, 10b, 10c activating the phase comparator circuit 2 when the input signal RD is existing and stopping the locking of the phase comparator circuit 2 when the input of the input signal RD is lost for a predetermined time to control the voltage-controlled oscillator 6 so as to be in operation at a predetermined frequency. |
