A Single-Ended PAM-4 Transmitter Using Unstacked Tailless CML Driver and Coefficient-Corrected FFE for Memory Interfaces

IF 5.2 1区工程技术 Q1 ENGINEERING, ELECTRICAL & ELECTRONIC

IEEE Transactions on Circuits and Systems I: Regular Papers Pub Date : 2024-09-04 DOI:10.1109/TCSI.2024.3450875

Yong-Un Jeong;Joo-Hyung Chae

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Abstract

This paper presents a single-ended four-level pulse-amplitude modulation (PAM-4) transmitter using an unstacked tailless current-mode logic (CML) driver for memory interfaces. Compared with the voltage-mode (VM) driver commonly used for single-ended memory interfaces, the proposed CML driver has stable termination for impedance matching and a small pre-driver with low dynamic power consumption, which allow the transmitter to achieve a higher data rate and a better total energy efficiency. The unstacked driver structure with an auxiliary leg and a current calibration scheme leads to high PAM-4 linearity by compensating for channel-length modulation that causes current source variation while occupying a small area. The strength of the feed-forward equalization (FFE) distorted by channel-length modulation is also compensated by an additional pulse of the proposed coefficient-corrected equalization. A prototype chip fabricated in a 65-nm CMOS process has an area of 0.0172 mm

$^{2}{}$

. It achieves a data rate of 34 Gb/s/pin with an energy efficiency of 0.60 pJ/bit and a level separation mismatch ratio (RLM) of 0.987.

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一种单端 PAM-4 发射器，使用无堆叠无台阶 CML 驱动器和用于存储器接口的系数校正 FFE

本文介绍了一种单端四电平脉冲幅度调制（PAM-4）发射器，它采用了用于存储器接口的非堆叠无尾电流模式逻辑（CML）驱动器。与单端存储器接口常用的电压模式（VM）驱动器相比，所提出的 CML 驱动器具有用于阻抗匹配的稳定端接和低动态功耗的小型前置驱动器，从而使发射器能够实现更高的数据传输速率和更好的总能效。带有辅助脚和电流校准方案的非堆叠驱动器结构可补偿导致电流源变化的信道长度调制，从而实现较高的 PAM-4 线性度，同时占用较小的面积。由信道长度调制引起的前馈均衡（FFE）强度失真也可通过拟议的系数校正均衡附加脉冲得到补偿。采用 65 纳米 CMOS 工艺制造的原型芯片面积为 0.0172 mm $^{2}{}$，数据传输率为 34 Gb/s/pin，能效为 0.60 pJ/bit，电平分离失配比 (RLM) 为 0.987。

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来源期刊

IEEE Transactions on Circuits and Systems I: Regular Papers 工程技术-工程：电子与电气

CiteScore

9.80

自引率

11.80%

发文量

441

审稿时长

2 months

期刊介绍： TCAS I publishes regular papers in the field specified by the theory, analysis, design, and practical implementations of circuits, and the application of circuit techniques to systems and to signal processing. Included is the whole spectrum from basic scientific theory to industrial applications. The field of interest covered includes: - Circuits: Analog, Digital and Mixed Signal Circuits and Systems - Nonlinear Circuits and Systems, Integrated Sensors, MEMS and Systems on Chip, Nanoscale Circuits and Systems, Optoelectronic - Circuits and Systems, Power Electronics and Systems - Software for Analog-and-Logic Circuits and Systems - Control aspects of Circuits and Systems.