Edge and Data Adaptive Equalization of Serial-Link Transceivers

Abstract

Limited channel bandwidth introduces inter-symbol interference (ISI) at both data and edge samples. In addition to the ISI at data samples, ISI at the edge samples (edge ISI) increases the bit error rate (BER) by degrading on the eye diagram and in- creasing the jitter of the clock and data recovery (CDR). This work proposes a forward FIR equalizer and a decision-feedback equal- izer (DFE) that compensate for both data and edge samples. To adapt both the data and edge equalizers, a modified LMS adapta- tion algorithm is introduced to achieve convergence. A transmitter and receiver are implemented in 0.13 m and 0.18 m technolo- gies respectively. The edge ISI is improved by 20% and the jitter is improved by 10% in measurement. The link operates over a 120 FR4 channel with 24 dB attenuation at Nyquist frequency, and the BER is below /49/48 /49/52at 3.6 Gb/s.