A 5-Gb/s 156-mW Transceiver with FFE/Analog Equalizer in 90-nm CMOS Technology

A 5-Gb/s transceiver in 90nm technology has been presented in this paper. To mitigate the effects of channel loss, a 4-tap feed-forward equalizer (FFE) is included in the transmitter. Meanwhile, the receiver employs continuous-time linear equalizer (CTLE) to amplify high frequency signal. The clocks of the transmitter are supplied by Phase-Locked Loops (PLL) while clocks in the receiver are provided by clock recover circuit (CDR). To facilitate the testing, built-in pseudo-random sequence (PRBS) generator and PRBS detector are integrated in this chip. Fabricated in 90nm CMOS technology, the transceiver consumes 156mW under 1.2V supply. Introduction With the rapid development of wire-line communication, data rates grow exponentially over the past decades, especially in digital computing and signal processing fields. In order to meet the growing demand for high-speed data transmission, Serdes (Serializer/Deserializer) is gradually replacing the traditional parallel buses and becoming the mainstream of high-speed interface. Serdes is a kind of multiplexing technology that converts data from parallel to serial, reducing the communication channels and chip pins. In inter-chip communication over PCB or backplane, avoiding reflection and Inter-Symbol Interference (ISI) are the main challenges for robust communication. Reflection in transmission line (T-line) can be reduced by proper T-line design. But ISI stems from Low-Pass Filter (LPF) characteristics of the actual line and becomes severe as either the data rate or the length of the T-line increases. Hence, ISI compensation is critical in over 5-Gb/s data communication. Equalizers in transmitter and receiver are necessary for compensation of ISI. This paper describes the design of key elements of a 5-Gb/s transceiver. The transceiver uses fixed transmitter feed-forward equalizer (FFE) in combination with analog equalizer in the receiver for line equalization. A system design overview including a description of FFE, analog equalizer and the transceiver architecture will be given. Next, the key circuit components of the transceiver will be described in detail. These components include the FFE-based transmitter equalizer, a linear receiver analog front-end with Continuous-Time Linear Equalizer (CTLE), Limiting Amplify (LA) and Slicer. Fabricated in 90-nm CMOS technology, the transceiver dissipates 156mW from a 1.2V supply and Phase-Locked Loops (PLL) is integrated on chip in this paper. Structure of Transceiver The transceiver architecture is shown in Fig.1. The transmitter is composed of 8:1 multiplexer (MUX) and pre-emphasized circuit. The transmitter FFE has programmable tap settings that are normally set to fixed values. The receiver includes analog equalizer, slicer and 1:8 demultiplexer (DEMUX). The receiver implements asynchronous local clock recovery using off-chip clock recover circuit (CDR). The 50-Ω single-end line terminations may be ac or dc coupled to the external line. The transmitter dissipates 72mW and produces an amplitude of 550 mV peak-to-peak differential (mVppd) into a 100-Ω differential load. 4th International Conference on Computer, Mechatronics, Control and Electronic Engineering (ICCMCEE 2015) © 2015. The authors Published by Atlantis Press 833