A Single-Ended Parallel Transceiver With Four-Bit Four-Wire Four-Level Balanced Coding for the Point-to-Point DRAM Interface

A four-bit four-wire four-level (4B4W4L) single-ended parallel transceiver for the point-to-point DRAM interface achieved a peak reduction of ~10 dB in the electromagnetic interference (EMI) H-field power, compared to a conventional 4-bit parallel binary transceiver with the same output driver power of transmitter (TX) and the same input voltage margin of receiver (RX). A four-level balanced coding is used in this work to minimize the simultaneous switching noise at TX, to utilize a differential sensing without a reference voltage at RX, to maintain the pin efficiency of 100%, and also to reduce EMI by setting the sum of currents through the four wires to be zero. A capacitive pre-emphasis scheme modified for four-level signaling is also used at TX to compensate for inter-symbol interference. The transmitted four-level signals are recovered by six differential comparators with an offset compensation and a decoder at RX. The proposed transceiver chip fabricated in a 65 nm CMOS process consumes 2.39 pJ/bit with a 1.2 V supply and a 2 inch FR4 channel at 8 Gb/s.