A 33-Gb/s/Pin 1.09-pJ/Bit Single-Ended PAM-3 Transceiver With Ground-Referenced Signaling and Time-Domain Decision Technique for Multi-Chip Module

Abstract

A three-level pulse amplitude modulation (PAM-3) transceiver (TRX) with improved simultaneous switching out- put (SSO) noise and reference voltage margin was studied. PAM-3 signaling with an insertion of 3 bits in 2-unit intervals (UI) was implemented using the upper, under, and ground voltages, achiev- ing 150% pin efficiency. The ground-referenced signaling (GRS) charge pump driver reduced SSO noise and maintained ground as the solitary return current path. Capacitive peaking and middle edge-rate boosting were implemented for transmitter (TX) equalization. With the receiver (RX), the ground level was used as a reference voltage for a single-to-differential (S2D) amplifier. PAM-3 signaling was converted to binary data using the time- domain decision technique in comparators. The decision time of comparators for data and reference voltage was compared. This technique shows the increased voltage margin, the reduced decision time, and the decreased error rate. The reduced decision time improved the performance of the PAM-3 decision feedback equalizer (DFE). A clock disabled the circuit, and a low-power return-to-zero (RZ) to non-RZ (NRZ) converter was config- ured for the proposed comparator output cases. The prototype TRX was fabricated in a 28-nm complementary metal–oxide silicon (CMOS) process with a surface area of 0.006 mm 2. The total power efficiency was recorded as 1.09 pJ/b at 33 Gb/s/pin. Through the flame retardant-4 (FR-4) 20-mm printed circuit board (PCB) channel a