| 摘要 |
PROBLEM TO BE SOLVED: To provide a phase locked loop which is the mode change-over type of a high-speed mode and low-noise mode. SOLUTION: Plural number of charge pumps CP1 and CP2 are connected to a loop filter, so as to hold at least one resistance r2 between a current output terminal and capacitance c1. Nand and nor in the outputs PU and PD of a phase frequency comparator 1 are obtained, a nor signal is adopted as the clock of D-FF64 and a signal obtained by delaying a nand signal by a delay element 63 for the portion of a short time dt is adopted as data of D-FF64, so that lock detection is executed. Based on this, the conductivity of the charge pump CP2 is controlled. The both of the loop band and a zero point of an open loop transmission function are changed only by changing the current value of the charge pump CP2. |
