A 10.4–16-Gb/s Reference-Less Baud-Rate Digital CDR With One-Tap DFE Using a Wide-Range FD

Abstract

A 10.4-16-Gb/s reference-less and baud-rate clock and data recovery (CDR) circuit with a one-tap speculative decision feedback equalizer (DFE) is presented. The quarter-rate CDR circuit uses a pattern-based phase detector (PD) and the proposed FD. This wide-range FD is composed of a coarse FD and a fine FD (FFD) which share the same front-end comparators with the PD and the DFE. Thus, no extra comparators are required. In addition, by monitoring the drift direction of five samples on the five-bit data patterns, the FFD performs an error-free operation within a frequency error of 7.7%. Therefore, the CDR has a robust FD-to-PD transition. By using the proposed FD, this CDR circuit not only achieves a wide frequency capture range of 43%, but also has a short frequency settling time of $680~\mu \text{s}$ . This CDR circuit is fabricated in 40-nm CMOS technology and occupies an active area of 0.1004 mm2. The total power of the receiver is 39.9mW at 16 Gb/s, and the calculated energy efficiency is 2.49pJ/b.