6.8 A 100Gb/s NRZ Transmitter with 8-Tap FFE Using a 7b DAC in 40nm CMOS

Abstract

Recently, PAM-4 transmitters have been realized at 112Gb/s or even faster to satisfy the continuously growing demands for wireline communications [1]-[5]. Although PAM-4 signaling performs two-fold bandwidth efficiency compared with the NRZ counterpart, the NRZ signal still has the advantage in low-loss scenarios like ultra-short-reach (USR) interconnection for optical engines due to its high output swing and better SNR. This paper presents a 100Gb/s NRZ transmitter fabricated in 40nm CMOS by incorporating a 7b DAC with an 8-tap FFE implemented in DSP. The DAC-based architecture demonstrates high resolution for FFE coefficients, achieving an output eye diagram with 73mV eye height and 760fs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> jitter under 7.1dB loss at 50GHz while consuming 619mW of power from 1.1V/1.2V/1.5V supplies.