PURPOSE: To optimize the band characteristic (cut-off frequency) of an LPF corresponding to a system by using an SCF as the LPF to integrate a phase comparing output waveform and to generate the control voltage of a voltage controlled oscillator and further providing a means to vary the period of a clock signal to be applied to this SCF.

CONSTITUTION: A function block is equipped with an LPF 14 realized by the SCF and a programmable divider 13 for SCF to supply the clock signal to the LPF 14. A data set circuit 6 to set the frequency dividing ratio of the programmable divider 13 for SCF can be shared to set the frequency dividing ratio of a programmable divider 5 for frequency division to an output fIN of a VCO 1. In such a circuit, since the frequency dividing ratio of the programmable divider 13 for SCF can be freely set through the data set circuit 6 by external data 11, the clock signal to be applied to the LPF 14 by the SCF can be made variable.