Patent ID: 7283602

Claim:
A half-rate clock and data recovery (CDR) circuit including; a half-rate phase detector for detecting phases of an input signal and a half rate clock and producing a comparison signal; a charge pump circuit receiving the comparison signal and, in response, producing a pump signal; a low-pass filter receiving and filtering the pump signal to produce a control signal; and a voltage controlled oscillator receiving the control signal and, in response, generating the half-rate clock and feeding the half-rate clock back to the half-rate phase detector, the half-rate phase detector comprising a first-stage latch circuit receiving the input signal and a second-stage latch circuit receiving an output of the first-stage latch circuit, an additional first-stage latch circuit receiving the input signal and an additional second-stage latch circuit receiving an output of the additional first-stage latch circuit, a selector circuit which receives an output of the first-stage latch circuit and an output of the additional first-stage latch circuit and outputs, in response, a re-timed signal synchronous with the half-rate clock and identical in array to the input signal, a first exclusive OR circuit which receives an output of the second-stage latch circuit and an output of the additional second-stage latch circuit and outputs a reference signal in response; a latch delay circuit in a though-data path and receiving the input signal, a one-pulse delay circuit in the through-data path, receiving an output of the latch delay circuit, generating a delay of one half-rate clock pulse, and outputting through-data, thereby converting phase comparison polarity in the half-rate phase detector, and a second exclusive OR circuit which receives the re-timed signal from the selector circuit and the though-data from the one-pulse delay circuit and outputs, in response, an output signal, wherein the voltage controlled oscillator is an N type LC voltage controlled oscillator for operation with the phase comparison polarity inversion produced by the one-pulse delay circuit.