Title :
A 10-Gb/sec unclocked current-mode logic (CML) analog decision-feedback equalizer (ADFE) in 0.18-μm CMOS
Author :
Chandramouli, Soumya ; Bien, Franklin ; Kim, Hyoungsoo ; Gebara, Edward ; Laskar, Joy
Author_Institution :
Georgia Inst. of Technol., Atlanta
Abstract :
An unclocked analog decision-feedback equalizer (ADFE) is implemented in a 0.18-mum 40 GHz ft CMOS process to equalize legacy FR-4 backplane channels at 8~10-Gb/sec. The critical first feedback-loop latency requirement of the DFE is met by using a novel unclocked feedback topology and current-mode logic (CML) circuit building blocks. The circuit consists of a 4-tap linear analog feed-forward filter that cancels pre-cursor inter-symbol interference (ISI) to partially open the eye and a novel 1-tap analog tunable CML feedback filter that enables cancellation of the first post-cursor at 10-Gb/sec without the use of smaller process nodes or speculative techniques. The chip with pads occupies 1.04 mm2 and draws 240 mA DC current from a 1.8 V supply at a typical process corner. The ADFE is used to equalize 20 inches of FR-4 backplane traces at 8-Gb/sec and 10-Gb/sec.
Keywords :
CMOS analogue integrated circuits; circuit feedback; current-mode logic; decision feedback equalisers; integrated circuit design; 1-tap analog tunable CML feedback filter; 4-tap linear analog feed-forward filter; CMOS process; analog decision-feedback equalizer; bit rate 10 Gbit/s; bit rate 8 Gbit/s; critical first feedback-loop latency requirement; current 240 mA; frequency 40 GHz; legacy FR-4 backplane channels; pre-cursor inter-symbol interference; size 0.18 mum; unclocked current-mode logic; unclocked feedback topology; voltage 1.8 V; Backplanes; CMOS logic circuits; CMOS process; Circuit topology; Decision feedback equalizers; Delay; Feedback circuits; Interference cancellation; Logic circuits; Nonlinear filters;
Conference_Titel :
Solid State Circuits Conference, 2007. ESSCIRC 2007. 33rd European
Conference_Location :
Munich
Print_ISBN :
978-1-4244-1125-2
DOI :
10.1109/ESSCIRC.2007.4430354