Patent ID: 7751521

Claim:
A clock and data recovery apparatus, the apparatus comprising: a first loop including a frequency/phase detection unit, a first charge pump unit, a multiplexing unit, a filtering unit, and a voltage controlled oscillator unit operating at a speed ¼ as fast as a speed of received data, wherein the first loop initializes the voltage controlled oscillator unit until an initial oscillation frequency of the voltage controlled oscillator unit is initialized and in case where no data is received; a second loop having a phase detection unit operating at a speed ¼ as fast as the speed of received data, a second charge pump unit suitable for the phase detection unit, the multiplexing unit, the filtering unit, and the voltage controlled oscillator unit operating at a speed ¼ as fast as the speed of received data, wherein the second loop is configured to operate during a normal reception of data after initialization of the initial oscillation frequency of the voltage controlled oscillator unit; a frequency lock detection unit for judging whether a frequency of a feedback clock signal falls within a desired frequency range, by comparing the frequency of the feedback clock signal with a frequency of a reference clock signal, and controlling the multiplexing unit to selectively operate one of the first loop and the second loop; and a data recovery unit for recovering data from received data by using the feedback clock signal from the voltage controlled oscillator unit, wherein the second charge pump is operated suitably for the phase detection unit that operates at a speed ¼ as fast as the speed of received data, and a ratio between an up-current and a down-current is ⅔.