A 2-Tap Half-Rate 25Gb/s Adaptive DFE in 55nm CMOS

To address signal integrity degradation in highspeed serial links, this paper presents a $25 \mathrm{~Gb} / \mathrm{s}$ adaptive decision-feedback equalizer (DFE) implemented in 55 nm CMOS technology. The proposed architecture employs a half-rate 2-tap topology to alleviate critical timing constraints in the feedback path, utilizing current-mode logic (CML) circuits for high-speed operation. An analog least mean squares algorithm (LMS) based adaptation engine continuously optimizes tap coefficients, incorporating a LMS algorithm to reduce hardware complexity. The core circuit integrates CML-based current-summing adders and master-slave D-flip-flops (MSDFF) with inductive peaking, while the adaptive module combines a sense amplifier (SA) for error detection and Gilbert-cell multipliers with Gm-C integrators for coefficient updates.