PHASE LOCKED LOOP APPARATUS

摘要

PURPOSE: A phase locked loop(PLL) apparatus is provided to reduce a time for synchronizing phases by controlling an outside current flowing from a charge pump. CONSTITUTION: A phase comparing unit(10) compares a phase of a modulated input signal and an output frequency of a voltage control oscillator and outputs a signal to the voltage control oscillator. A charge pump generates a current according to the signal from the phase comparing unit(10) and outputs a signal being applicable to it. A low filter receives the signal from the charge pump and performs a low pass filtering. The voltage control oscillator controls an output frequency by using a voltage outputted through the low filter. The charge pump comprises a charge and discharge speed controlling unit(30). The charge and discharge speed controlling unit(30) controls a charge and discharge speed by controlling an amount of a flowing current according to a selection of a predetermined unit among a charge and discharge circuit of N unit by using an external control signal.