| 摘要 |
PURPOSE:To attain the synchronization even when the variable range of a VCO oscillating frequency by a loop filter is made narrow by varying sequentially the self-running frequency of a voltage controlled oscillator(VCO) sequentially through the operation of the clock recovery circuit. CONSTITUTION:When a charging voltage F of a capacitor 66 reaches a reference voltage Vref, a voltage comparator 74 outputs a high level, a clock is outputted to a flip-flop 78 and signals A, B are both inverted. A P-channel MOSFET 62 is turned off at this point of time, an N-channel MOSFET 64 is turned on, a capacitor 60 is discharged, a P-channel MOSFET 68 is turned on, an N- channel MOSFET 70 is turned off and a capacitor 72 starts charging. When the charging voltage of the capacitor 72 reaches the reference voltage Vref, the output of a voltage comparator 76 goes to a high level and the output of the flip-flop 78 is inverted. Thus, the charging speed of the capacitor 66 is changed according to a control voltage and a 2nd control voltage to control an output frequency. |
