A 5.75 to 44 Gb/s Quarter Rate CDR With Data Rate Selection in 90 nm Bulk CMOS

This paper presents a quarter-rate clock and data recovery (CDR) circuit for plesiochronous serial I/O-links. The 2$times$-oversampling phase-tracking CDR, implemented in 90$,$nm bulk CMOS technology, covers the whole range of data rates from 5.75 to 44 Gb/s realized in a single IC by the novel feature of a data rate selection logic. Input data are sampled with eight parallel differential master-slave flip-flops, where bandwidth enhancement techniques were necessary for 90 nm CMOS. Precise and low-jitter local clock phases are generated by an analog delay-locked loop. These clock phases are aligned to the incoming data by four parallel phase rotators. The phase-tracking loop of the CDR is realized as a digital delay-locked loop and is therefore immune against process tolerances. The CDR is able to track a maximum frequency deviation of ${pm }{hbox{615~ppm}}$ between incoming data and a local reference clock and fulfills the extended XAUI jitter tolerance mask. A bit error rate ${?} hbox{10}^{-12}$ was verified up to 38 Gb/s using a 2$ ^{7} -$1 PRBS pattern. With a low power consumption per data rate of only 5.74 mW/(Gb/s) the CDR meets the specifications of the International Technology Roadmap for Semiconductors for 90$~$nm CMOS serial I/O-links at the maximal data rate of 44 Gb/s. The CDR occupies a chip area of 0.2 ${hbox{mm}}^{2}$ .