A Referenceless Digital CDR with a Half-Rate Jitter-Tolerant FD and a Multi-Bit Decimator

A referenceless digital clock and data recovery (D-CDR) circuit using a half-rate jitter-tolerant frequency detector (FD) and a multi-bit decimator is presented. For a referenceless configura-tion, we introduced a half-rate jitter-tolerant digital quadricorrelator frequency detector (JT-DQFD). Additionally, we proposed a multi-bit decimator circuit that losslessly down-samples up/down data from a phase detector to reduce the recovered clock jitter. The down-sampled multi-bit phase information is processed by a digital loop filter to adjust the phase of the recovered clock. Fabricated in a 28-nm CMOS technology, the test chip achieves a power efficiency of 1.3 pJ/bit at 10 Gb/s.