A 28-Gb/s 4-Tap FFE/15-Tap DFE Serial Link Transceiver in 32-nm SOI CMOS Technology

This paper presents a 28-Gb/s transceiver in 32-nm SOI CMOS technology for chip-to-chip communications over high-loss electrical channels such as backplanes. The equalization needed for such applications is provided by a 4-tap baud-spaced feed-forward equalizer (FFE) in the transmitter and a two-stage peaking amplifier and 15-tap decision-feedback equalizer (DFE) in the receiver. The transmitter employs a source-series terminated (SST) driver topology which doubles the speed of existing half-rate designs. The high-frequency boost provided by the peaking amplifier is enhanced by adopting a structure with capacitively coupled parallel input stages and active feedback. A capacitive level-shifting technique is introduced in the half-rate DFE which allows a single current-integrating summer to drive the four parallel paths used for speculating the first two DFE taps. Error-free signaling at 28 Gb/s is demonstrated with the transceiver over a channel with 35 dB loss at half-baud frequency. In a four-port core configuration, the power consumption at 28 Gb/s is 693 mW/lane.