A 76-Gb/s DSP-DAC-Based Discrete Multitone Wireline Transmitter in 5-nm FinFET

Abstract

This article presents a 76-Gb/s digital-to-analog converter (DAC)-based discrete multitone (DMT) wireline transmitter (TX) fabricated in 5-nm FinFET. The TX employs a 16-way parallel multi-path delay feedback (MDF) inverse fast Fourier transform (IFFT) processor for area-efficient implementation. The TX digital signal processor (DSP) includes on-chip bit/power-loading and cyclic-prefix (CP) insertion logic and supports 4- to 256-QAM modulation formats across 31 orthogonal subchannels. The time-domain DMT samples generated by the TX DSP are converted into analog waveform using a source-series termination (SST)-based DAC. The prototype is demonstrated over a channel with 9.7-dB insertion loss (IL) at Nyquist, achieving a bit error rate (BER) of 2.1E-4 with a total power consumption of 144 mW from 0.735-V digital and 0.725-V analog supplies, resulting in an energy efficiency of 1.89 pJ/b. The proposed DMT TX improves bandwidth efficiency and signal-to-noise ratio (SNR) over conventional pulse-amplitude modulation (PAM)-based transmitters by employing frequency-domain modulation and equalization. This work is the first demonstration of a DAC-based DMT TX operating at >76 Gb/s fabricated in advanced CMOS technology.