A 32-Gb/s 0.46-pJ/bit PAM4 CDR Using a Quarter-Rate Linear Phase Detector and a Self-Biased PLL-Based Multiphase Clock Generator
Zhao Zhang, Guang Zhu, Can Wang, Li Wang, C. Patrick Yue
Abstract
This article presents a four-level pulse-amplitude modulation (PAM4) quarter-rate clock and data recovery circuit (CDR). A quarter-rate linear phase detector (QLPD) is proposed to reduce the recovered clock jitter by removing the dithering jitter of the bang-bang PD. A self-biased phase-locked loop (PLL)-based multiphase clock generator (MCG) with a very wide loop bandwidth (around 600 MHz) is proposed to reduce the MCG power consumption and generate a low-jitter multiphase clock for the quarter-rate operation. Fabricated in a 40-nm CMOS process, the prototype achieves a bit efficiency of 0.46 pJ/bit at 32-Gb/s input data rate. The measured jitter tolerance (JTOL) at the bit error rate (BER) of <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> is higher than 0.35 UIPP with the corner frequency at about 10 MHz. The measured integrated jitter of the 4-GHz recovered clock is 352.6 fs.