Clock generator and data recovery circuit using the same

A clock generator for generating a sampling clock according to an input signal and a reference clock, the clock generator comprising:

• a voltage control oscillator for generating a sampling clock and a plurality of multi-phase clocks;
• a multiplexer for receiving the multi-phase clocks and selecting one of the multi-phase clocks to generate a selected clock according to a selection signal;
• a phase-frequency detector for receiving the selected clock and the reference clock and generating a phase-frequency error signal;
• a charge pump and loop filter for receiving the phase-frequency error signal and generating a control voltage;
• a phase detector for receiving the sampling clock and the input signal and generating a phase error signal;
• and
• a digital low-pass filter for receiving the phase error signal and generating the selection signal,
• wherein the voltage control oscillator receives the control voltage to generate the sampling clock and the plurality of multi-phase clocks, and when the digital low-pass filter generates the selection signal to force the multiplexer to change a phase, the digital low-pass filter clears an accumulated phase error therein.

A data recovery circuit, comprising:

• a voltage controlled oscillation loop for receiving a reference clock and generating a sampling clock;
• and
• a data recovery loop for generating the selection signal according to the sampling clock and an input signal;
• the voltage controlled oscillation loop comprising a multi-phase voltage control oscillator for generating a plurality of clock signals with different phases and selecting one of the clock signals according to a selection signal;
• the data recovery loop comprising:
• a phase detector for generating a phase error signal according to the sampling clock and the input signal;
• and
• a digital low-pass filter for generating the selection signal according to the phase error signal;
• wherein when the digital low-pass filter generates the selection signal to direct the multi-phase voltage control oscillator to change a selected phase, the digital low-pass filter clears an accumulated phase error therein.