A Maximum-Eye-Tracking CDR with Biased Data-Level and Eye Slope Detector for Optimal Timing Adaptation

Abstract

In this paper, a maximum-eye-tracking CDR (MET-CDR) for minimum bit error rate (BER) is presented. The proposed CDR does not require a BER counter or eye-opening monitor to find the optimal sampling phase. The biased datalevel obtained from the weighted sum of UP and DN is proposed to extract the actual eye height information considering the precursor ISI. Two error samples with small time spacing detect the current eye height and the slope of the eye height so that the CDR tracks the maximum eye height where the slope becomes zero. Measured results prove that the maximum eye height phase and the minimum BER phase matches well. A prototype receiver fabricated in 28-nm CMOS process operates at 26Gb/s with an eye-opening of 25% UI and consumes 87mW while equalizing 21dB of loss at 13GHz.