A 0.190-pJ/bit 25.2-Gb/s/wire Inverter-Based AC-Coupled Transceiver for Short-Reach Die-to-Die Interfaces in 5-nm CMOS
Yoshinori Nishi, John W. Poulton, Walker J. Turner, Xi Chen, Sanquan Song, Brian Zimmer, Stephen G. Tell, Nikola Nedovic, John Wilson, William J. Dally, C. Thomas Gray
Abstract
This article presents an inverter-based short-reach ac-coupled toggle (ISR-ACT) link targeted for short-reach die-to-die communication over silicon interposer or similar high-density interconnect. The ISR-ACT’s transmitter (TX) sends non-return-to-zero (NRZ) data through a small series capacitor to inject low-swing pulses into the line. These pulses are amplified and latched by a two-stage receiver (RX), where the 1st-stage transimpedance amplifier (TIA) amplifies the pulse data and positive feedback around both stages captures the data and maintains the dc level on the line. Achieving low signal swing through a capacitor divider, the ACT driver consumes less than half the power compared to regular rail-to-rail CMOS drivers while providing dc voltage isolation between the driver and the RX. Fabricated in a 5-nm standard CMOS process, the ISR-ACT link, operating on a 0.75-V supply, shows 0.66 UI margin at 25.2 Gb/s/wire over a 1.2-mm on-chip channel and demonstrates an energy efficiency of 0.190 pJ/bit.