PLL CONTROL CIRCUIT AND METHOD OF CONTROLLING THE SAME

摘要

A PLL(Phase Locked Loop) controlling circuit and a method for the same are provided to output the optimum coefficient regardless of the type of video signal by detecting the state of an error according to phase error between a horizontal sync signal of an input video signal and a reference signal and changing a coefficient corresponding to the detected state. A PLL controlling circuit(10) is composed of an error amount detecting circuit(12) and a coefficient switching part(14). The PLL controlling circuit receives a phase error between a horizontal sync signal of a video signal and a reference signal. The error amount detecting circuit determines a critical value of the phase error using the N thresholds to output a control signal(104) indicating one of N+1 levels. The coefficient switching part outputs one of the N+1 gains as a coefficient signal, wherein the outputted gain corresponds to the level indicated by the control signal.