| 摘要 |
<P>PROBLEM TO BE SOLVED: To speed up lock-up in a phase synchronization circuit. <P>SOLUTION: A phase synchronization circuit 100 has an output frequency available by multiplying the frequency of reference signal with X, and includes a reference signal source 180, a voltage control oscillator 110, a phase comparator 120, a first charge pump 130, a loop filter 150, a counter 161, a second charge pump 170, and a control circuit 164. The voltage control oscillator 110 generates a first signal and a second signal which is in opposite phase. A switch 140 supplies a current signal generated by the first charge pump 130 to the loop filter 150. The counter 161 counts the number of cycles of the second signal contained in one cycle period of the reference signal. The second charge pump 170 can supply a first current signal and a second current signal, having opposite signs from each other, to the loop filter 150. The control circuit 164 controls the switch 140 and the second charge pump 170 based on the comparison between the number of cycles and X value. <P>COPYRIGHT: (C)2012,JPO&INPIT |
