A 32-Gb/s High-Swing PAM-4 Current-Mode Driver with Current-Bleeding Cascode Technique and Capacitive-Coupled Pre-drivers in 40-nm CMOS for Short-Reach Wireline Communications

This paper describes a 32-Gb/s high-swing PAM4 transmit driver for short-reach wireline communications. The proposed current-mode transmitter utilizes the current-bleeding cascode technique to achieve the 1.4-V differential peak-to-peak swing without violating breakdown constraints. The transmitter bandwidth is enhanced by capacitive-coupled pre-drivers to maximize the cursor amplitude and signal-to-noise ratio. The transmitter test chip is fabricated in a 40-nm CMOS process and occupies 0.004 mm ² . The design achieves a 32-Gb/s data rate with 157-mV eye height and 2.3-pJ/bit energy efficiency.