A 4-20-Gb/s 1.87-pJ/b Continuous-Rate Digital CDR Circuit With Unlimited Frequency Acquisition Capability in 65-nm CMOS

A continuous-rate referenceless clock and data recovery (CDR) circuit with an unlimited frequency acquisition capability is presented. The proposed frequency detector (FD) is derived from a multi-phase oversampling FD. Through accurate analysis of the root causes limiting the capture range, the extension techniques are proposed and digitally implemented by a small hardware overhead. The FD achieve...