PHASE LOCKED LOOP APPARATUS

摘要

PURPOSE: To prevent a performance from deteriorating owing to a change of a parameter or a secular change by providing a phase comparator which generates a control signal supplied to an analog oscillator in response to one of an output signal of a analog oscillator and a multi-bit digital oscillation signal. CONSTITUTION: This device is equipped with a digital signal generating means 241 including a digital oscillator 230 which generates a digital oscillation signal representing sampled data consisting of bits having a frequency approximating a predetermined nominal frequency. Further, the device is equipped with a digital phase comparing means 252 which is coupled with a variable oscillator 256 and the digital signal generating means 241 and generates a phase difference signal proportional to the phase difference between an oscillation signal and a single-bit digital signal representing predetermined bits of the digital oscillation signal consisting of the bits and a means 254 which is coupled with the phase comparing means 252 and generates a control signal in response to the phase difference signal. Consequently, this phase-locked clock signal is stably generated.