Analog-DFE-based 16Gb/s SerDes in 40nm CMOS that operates across 34dB loss channels at Nyquist with a baud rate CDR and 1.2V<inf>pp</inf> voltage-mode driver

Abstract

In networking systems today data rates are increasing beyond 15Gb/s and yet the installed backplanes are made of low cost materials with losses in excess of 30dB at 7.5GHz. Standards, such as IEEE802.3ap-10GBASE-KR and OIF CEI25G, are specifying SerDes requirements for channels with 25dB loss at Nyquist and this has driven the development of SerDes with 4 or 5 tap DFEs. Until now, solutions for 34dB or more channel loss have been limited to 10.3Gb/s or below, whereas this paper describes an adaptive 14-tap DFE that achieves a 1017 BER across a 34dB loss channel at 16Gb/s for a power of 235mW/lane. A baud-rate CDR technique is specifically developed that gives excellent locking characteristics and alignment for use with a speculative DFE together with an enhanced swing TX voltage mode driver.