ISSCC 2006 / SESSION 18 / CLOCK AND DATA RECOVERY / 18 . 5 18 . 5 A 3 . 2 Gb / s Semi - Blind - Oversampling CDR

A blind-oversampling CDR tracks the high-frequency jitter of the input data stream, but is limited at low-frequencies by the size of its FIFO [1]. A phase-tracking CDR, on the other hand, tracks jitter at frequencies below f3dB of its loop filter, but performs poorly beyond this frequency [2]. In this paper, a semi-blind-oversampling technique is presented. The proposed technique produces a jitter tolerance equal to the product of the jitter tolerances of a phase-tracking CDR and a blind-oversampling CDR (see Fig. 18.5.1), thereby increasing the low-frequency jitter tolerance by a factor of 32 (limited by the FIFO size). This enhancement in lowfrequency jitter tolerance is essential to applications such as spread-spectrum clocking [3] where the clock edge can deviate from its nominal location by as many as a few hundred UIs.