A 112 Gb/s PAM-4 56 Gb/s NRZ Reconfigurable Transmitter With Three-Tap FFE in 10-nm FinFET

Abstract

This paper presents a reconfigurable 56 GS/s transmitter (TX) that operates up to 112 Gb/s with four-level pulse-amplitude modulation (PAM-4) and at 56 Gb/s with non- return-to-zero (NRZ) modulation scheme. Fabricated in the 10-nm FinFET technology, the TX incorporates a four-way inter- leaved quarter-rate architecture with a three-tap feed-forward equalizer (FFE). Key features of the TX include a 1-UI pulse- generator-based 4:1 serializer combined with a current-mode logic (CML) driver, low-power data-serializing paths, an out- put pad-network using a multi-segment π-coil for bandwidth co-optimization together with ESD diodes, sub-80-fs resolution duty-cycle detector/corrector (DCD/DCC) and quadrature-error detector/corrector (QED/QEC) circuits, and a hybrid LC-phase- locked loop (PLL) with quadrature clock distribution circuits. The TX operating at 112 Gb/s in PAM-4 modulation consumes 232 mW from 1- and 1.5-V supplies, achieving an 2.07 pJ/b energy efficiency. The TX front end occupies an area of 0.0302 mm 2.