A 1.69-pJ/b 14-Gb/s Digital Sub-Sampling CDR With Combined Adaptive Equalizer and Self-Error Corrector

Abstract

This paper presents an area-and energy-efficient digital sub-sampling clock and data recovery (CDR) with combined adaptive equalizer and self-error corrector (SEC). Using the digitized phase difference between the incoming data and the full-rate output clock of a digitally controlled oscillator (DCO) for both the equalizer adaptation and clock recovery loop, the proposed adaptive equalizer is combined with the CDR by sharing its adaptation loop including a sub-sampling phase detector (SSPD) and a digital logic circuit. Consequently, the active area and power dissipation for the adaptive equalizer are reduced. Furthermore, the SEC is proposed to improve the high-frequency jitter tolerance of the CDR. The SEC detects bit errors by observing the comparator decision and corrects the errors without any data encoding or complicate circuits. The out-of-band jitter tolerance is improved by 22.6% at 100 MHz for 17.2-dB loss channel with <10 -12 biterror rate (BER) with the proposed SEC. The SEC is applicable to various receivers with compact design at a low cost. The prototype receiver consumes 23.9 mW at 14-Gb/s and occupies 0.007 mm 2 in a 28-nm CMOS technology.INDEX TERMS Adaptive equalizer, clock and data recovery (CDR), continuous-time linear equalizer (CTLE), decision feedback equalizer (DFE), jitter tolerance, receiver, self-error corrector (SEC), subsampling.