| 摘要 |
PROBLEM TO BE SOLVED: To provide a PLL circuit capable of quickening a lockup time in an arbitrary set time while ensuring high C/N characteristics. SOLUTION: The current value Icp [A] of an output current signal Icp of a charge pump circuit 2 is switched synchronously with a timer signal flosw outputted by a fast lock timer circuit 7 within a set time set based on frequency- division rate setting data inputted form the outside part. In this case, when a timer signal flosw outputted from the fast lock timer circuit 7 is a high level, current quantity Icp [A] to be supplied to a low pass filter 3 is set so as to be a large value so that high speed lockup can be attained, and when the timer signal flosw outputted from the fast lock timer circuit 7 is a low level, the current quantity Icp [A] to be supplied to the low pass filter 3 is set so as to be a small value so that C/N can be improved. |
