| 摘要 |
PROBLEM TO BE SOLVED: To quickly shift the output of a VCO to a target frequency by opening a PLL loop until an output frequency of the VCO reaches the target frequency and outputting a fixed pump up signal or pump down signal. SOLUTION: When a control circuit 21 is set to a frequency that is higher than a present state by a frequency change key 20, the circuit 21 supervises that a comparison result from a 2nd phase phase comparator 7 changes from delay to progress (state where a pump up signal is changes to a pump down signal) from and that the comparison result from the comparator 7 changes from progress to delay when it is set to a frequency that is lower than the present state. And when it detects the change, it gives an L level signal to an inverter 9 and also resets a flip-flop 10 for up. With this, after this, 5th and 6th NAND circuits 16 and 17 output signals based on a comparison result of a 1st phase comparator 5 and a PLL loop is under closed control. |
