A 20-Gb/s Full-Rate Linear Clock and Data Recovery Circuit With Automatic Frequency Acquisition

A 20-Gb/s full-rate clock and data recovery circuit employing a mixer-type linear phase detector and automatic frequency locking technique is described. The phase detector achieves high-speed operation by mixing the clock with the data-transition pulses, providing output proportional to the phase error. The frequency acquisition loop utilizes the data phases rather than the clock phases to distill the frequency difference, and no external reference is used in this design. Fabricated in 90-nm CMOS technology, this circuit reveals rms and peak-to-peak jitter of 480 fs and 4.22 ps in response to a 2³¹ -1 PRBS on the recovered clock while consuming 154 mW from a 1.5-V supply.