Clock recovery circuit capable of automatically adjusting frequency range of a vco

Abstract

A clock recovery circuit capable of automatically adjusting the frequency range of a voltage-controlled oscillator (VCO). The clock recovery circuit includes a phase detector, a charge pump, a loop filter, a voltage-controlled oscillator, a frequency counter, and a frequency control unit. The phase detector receives an input signal, such as EFM clock, and a VCO clock and outputs a control signal according to phase differences between the EFM clock and the VCO clock. The charge pump controls the charge action according to the control signal. The loop filter is connected to the charge pump and outputs a voltage signal. The voltage-controlled oscillator receives the voltage signal from the loop filter and outputs the VCO clock. The frequency counter counts the frequency of the VCO clock and outputs an oscillation frequency. The frequency control unit receives the oscillation frequency, sets a frequency value according to the oscillation frequency, and outputs a control voltage to the voltage-controlled oscillator.