| 摘要 |
The present invention provides a dual mode phase and frequency detector for use with a charge pump and a loop filter. The charge pump is adapted to adjust charging or discharging of the loop filter to adjust a VCO for generating a digital clock. The dual mode phase and frequency detector includes a phase and frequency detector and a first delay element. The phase and frequency detector is arranged to receive the VCO clock for tracking a reference clock signal. The phase and frequency detector generates control signals in response to the VCO clock and the reference clock signal. The control signals control charging or discharging of a loop filter in a DLL when the phase and frequency detector is operating in a phase and frequency detector mode. The first delay element is coupled to receive one of the control signals from the phase and frequency detector for generating an auxiliary control signal in response to the VCO clock. The first delay element generates the auxiliary control signal when the phase and frequency detector is operating in a phase detector mode. In this arrangement, the auxiliary control signal and the control signals control the charge pumps to charge or discharge the loop filter for adjusting the digital clock of the VCO when the phase and frequency detector is operating in the phase detector mode.
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