PHASE SYNCHRONIZING CIRCUIT

摘要

A constant deciding part (90) decides a magnitude of a charge current to be outputted from a charge pump circuit (30), also decides a time constant of a loop filter (40) and further decides various constants of the gain of a voltage controlled oscillator (50) such that the damping factor and proportionality factor of the natural frequency of a phase synchronizing circuit are respective predetermined values for an input frequency of the phase synchronizing circuit. The constant deciding part (90) then outputs, based on those decisions, various control signals. The charge pump circuit (30), loop filter (40) and voltage controlled oscillator (50) change the magnitudes of the charge current, the time constants and the gains, respectively, in accordance with the control signals from the constant deciding part (90).