A 180-Mb/s to 3.2-Gb/s, continuous-rate, fast-locking CDR without using external reference clock

Abstract

A referenceless, continuous-rate, fast-locking CDR with an operating range of 180 Mb/s to 3.2 Gb/s is presented. The harmonic lock property of a rotational frequency detector and the maximum run-length limit of 8B10B encoded data are utilized to detect a harmonic lock and to accelerate acquisition process. A separate VCO control scheme is introduced to stabilize the loop with a modest amount of on-chip capacitance.