A Multi-Rate Burst-Mode CDR Using a GVCO With Symmetric Loops for Instantaneous Phase Locking in 65-nm CMOS

A multi-rate burst-mode clock and data recovery (BCDR) circuit based on a simple gated voltage-controlled oscillator (GVCO) is presented. A simple symmetric circuit topology makes the area for the GVCO smaller and leads to an easier timing design. The GVCO consists of two loops that operate complementarily. Circuit configurations of the same type are adopted for AND and OR in the loops to reduce the difficulties in the timing alignment of the signals from the loops. To confirm the validity of the proposed topology, we fabricated a BCDR IC with the 65-nm-MOSFET process. It can extract the 12.5-GHz clock signal from 12.5-Gb/s, 6.25-Gb/s, 3.125-Gb/s, 1.5625-Gb/s, and 781.25-Mb/s input data. Without a circuit for precise timing adjustment for the signals in the two loops, the IC provides instantaneous phase locking of 1 bit for burst data input of 12.5 Gb/s. The measured jitter is lower than 2 ps rms. The area and the power consumption for the core GVCO are 0.03 ${\bf mm}^{2}$ and 60 mW.