A 28/56 Gb/s NRZ/PAM-4 Dual-Mode Transceiver in 28-nm CMOS.

A 28/56 Gb/s NRZ/PAM-4 Dual-mode Transceiver (TRx) in a 28-nm CMOS process is presented. The quarter-rate transmitter (TX) incorporates a voltage-mode driver with a 4-tap feed forward equalizer (FFE). The half-rate receiver (RX) employs a continuous-time linear equalizer (CTLE), a 3-stage high-speed slicer and a digital clock and data recovery (CDR). A high-speed track-and-regenerate comparator is proposed to improve the settling time in the RX slicer. Measured results show that the TRx achieves 56 Gb/s maximum data rate with chip-on-board assembly. The TX and RX dissipate 125mW and 181.4mW power from a 0.9V supply, respectively.