A 2.5 Gb/s Run-Length-Tolerant Burst-Mode CDR Based on a 1/8th-Rate Dual Pulse Ring Oscillator

A 2.5 Gb/s burst-mode clock and data recovery (CDR) circuit is presented that uses a 1/8th-rate ring oscillator with two pulses running simultaneously that are phase independent. One “tune” pulse sets the delay of the ring by phase locking it to a reference. The other “clock” pulse tracks the phase of the incoming data by a process of pulse removal and reinsertion. Because both pulses share the same ring, there is no frequency mismatch between the incoming data stream and the recovered clock in frequency synchronous systems, allowing for large data run lengths. A 1:8 data-demux clock is naturally generated by tapping the clock pulse along the ring. Phase acquisition is instantaneous from a single data edge. Run length tolerance is larger than 72 bits. The 0.6 mm$^{2}$ 0.13 $mu$m CMOS chip includes a CML-to-CMOS input buffer, PLL with on-chip loop filter, PRBS checker, 1:8 data demux, and eight output buffers. It has 2.7 ${rm UI}_{rm pp}$ measured jitter tolerance at 100 kHz and consumes 42 mW from a single 1.2 V supply.