PHASE DETECTOR AND PLL-CIRCUIT COMPRISING SUCH PHASE DETECTOR

摘要

PHA 1110 12 22.05.1985 Phase detector and PLL circuit comprising such phase detector. Phase locked loop (PLL) circuits are widely used for data carrier extraction in many applications. Conventional PLL's have the disadvantage that the VCO oscillating frequency will be driven to its minimal or maximal frequency when the input data signal is absent and therefore the locking to a new data signal takes a relatively long time. This is unacceptable in applications where the input data signal often is interrupted and a fast locking is required (e.g. PLL circuits in disk controllers). The invention presents a new PLL circuit and a new phase detector for preventing the long lock acquisition times by controlling the VCO by a predetermined reference frequency when the data input signal is absent.