A half-rate clock and data recovery circuit includes a phase detector capable
of
operating at a half-rate, a charge pump circuit, a low pass filter, and a voltage
controlled oscillator. The phase detector includes a selector circuit which receives
uninverted and inverted signals from respective latches of the phase detector and
an uninverted and inverted half-rate clock and outputs uninverted and inverted
retimed signals supplied to the charge pump so that the charge pump produces a
full-rate output in response to a half-rate input. The circuit provides greater
operating margin.