8 research outputs found

    A 2-40 Gb/s PAM4/NRZ dual-mode wireline transmitter with 4:1 MUX in 65-nm CMOS

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    This paper presents a 2-40 Gb/s dual-mode wireline transmitter supporting the four-level pulse amplitude modulation (PAM4) and non-return-to-zero (NRZ) modulation with a multiplexer (MUX)-based two-tap feed-forward equalizer (FFE). An edge-acceleration technique is proposed for the 4:1 MUX to increase the bandwidth. By utilizing a dedicated cascode current source, the output swing can achieve 900 mV with a level deviation of only 0.12% for PAM4. Fabricated in a 65-nm CMOS process, the transmitter consumes 117 mW and 89 mW at 40 Gb/s in PAM4 and NRZ at 1.2 V supply. ยฉ 2018, Institute of Electronics Engineers of Korea. All rights reserved

    ๋Œ€์—ญํญ ์ฆ๋Œ€ ๊ธฐ์ˆ ์„ ์ด์šฉํ•œ ์ „๋ ฅ ํšจ์œจ์  ๊ณ ์† ์†ก์‹  ์‹œ์Šคํ…œ ์„ค๊ณ„

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    ํ•™์œ„๋…ผ๋ฌธ(๋ฐ•์‚ฌ) -- ์„œ์šธ๋Œ€ํ•™๊ต๋Œ€ํ•™์› : ๊ณต๊ณผ๋Œ€ํ•™ ์ „๊ธฐยท์ •๋ณด๊ณตํ•™๋ถ€, 2022.2. ์ •๋•๊ท .The high-speed interconnect at the datacenter is being more crucial as 400 Gb Ethernet standards are developed. At the high data rate, channel loss re-quires bandwidth extension techniques for transmitters, even for short-reach channels. On the other hand, as the importance of east-to-west connection is rising, the data center architectures are switching to spine-leaf from traditional ones. In this trend, the number of short-reach optical interconnect is expected to be dominant. The vertical-cavity surface-emitting laser (VCSEL) is a com-monly used optical modulator for short-reach interconnect. However, since VCSEL has low bandwidth and nonlinearity, the optical transmitter also needs bandwidth-increasing techniques. Additionally, the power consumption of data centers reaches a point of concern to affect climate change. Therefore, this the-sis focuses on high-speed, power-efficient transmitters for data center applica-tions. Before the presenting circuit design, bandwidth extension techniques such as fractionally-spaced feed-forward equalizer (FFE), on-chip transmission line, inductive peaking, and T-coil are mathematically analyzed for their effec-tiveness. For the first chip, a power and area-efficient pulse-amplitude modulation 4 (PAM-4) transmitter using 3-tap FFE based on a slow-wave transmission line is presented. A passive delay line is adopted for generating an equalizer tap to overcome the high clocking power consumption. The transmission line achieves a high slow-wave factor of 15 with double floating metal shields around the differential coplanar waveguide. The transmitter includes 4:1 multi-plexers (MUXs) and a quadrature clock generator for high-speed data genera-tion in a quarter-rate system. The 4:1 MUX utilizes a 2-UI pulse generator, and the input configuration is determined by qualitative analysis. The chip is fabri-cated in 65 nm CMOS technology and occupies an area of 0.151 mm2. The proposed transmitter system exhibits an energy efficiency of 3.03 pJ/b at the data rate of 48 Gb/s with PAM-4 signaling. The second chip presents a power-efficient PAM-4 VCSEL transmitter using 3-tap FFE and negative-k T-coil. The phase interpolators (PIs) generate frac-tionally-spaced FFE tap and correct quadrature phase error. The PAM-4 com-bining 8:1 MUX is proposed rather than combining at output driver with double 4:1 MUXs to reduce serializing power consumption. T-coils at the internal and output node increase the bandwidth and remove inter-symbol interference (ISI). The negative-k T-coil at the output network increases the bandwidth 1.61 times than without T-coil. The VCSEL driver is placed on the high VSS domain for anode driving and power reduction. The chip is fabricated in 40 nm CMOS technology. The proposed VCSEL transmitter operates up to 48 Gb/s NRZ and 64 Gb/s PAM-4 with the power efficiency of 3.03 pJ/b and 2.09 pJ/b, respec-tively.400Gb ์ด๋”๋„ท ํ‘œ์ค€์ด ๊ฐœ๋ฐœ๋จ์— ๋”ฐ๋ผ ๋ฐ์ดํ„ฐ ์„ผํ„ฐ์˜ ๊ณ ์† ์ƒํ˜ธ ์—ฐ๊ฒฐ์ด ๋”์šฑ ์ค‘์š”ํ•ด์ง€๊ณ  ์žˆ๋‹ค. ๋†’์€ ๋ฐ์ดํ„ฐ ์†๋„์—์„œ์˜ ์ฑ„๋„ ์†์‹ค์— ์˜ํ•ด ๋‹จ๊ฑฐ๋ฆฌ ์ฑ„๋„์˜ ๊ฒฝ์šฐ์—๋„ ์†ก์‹ ๊ธฐ์— ๋Œ€ํ•œ ๋Œ€์—ญํญ ํ™•์žฅ ๊ธฐ์ˆ ์ด ํ•„์š”ํ•˜๋‹ค. ํ•œํŽธ, ๋ฐ์ดํ„ฐ ์„ผํ„ฐ ๋‚ด ๋™-์„œ ์—ฐ๊ฒฐ์˜ ์ค‘์š”์„ฑ์ด ๋†’์•„์ง€๋ฉด์„œ ๋ฐ์ดํ„ฐ ์„ผํ„ฐ ์•„ํ‚คํ…์ฒ˜๊ฐ€ ๊ธฐ์กด์˜ ์•„ํ‚คํ…์ฒ˜์—์„œ ์ŠคํŒŒ์ธ-๋ฆฌํ”„๋กœ ์ „ํ™˜๋˜๊ณ  ์žˆ๋‹ค. ์ด๋Ÿฌํ•œ ์ถ”์„ธ์—์„œ ๋‹จ๊ฑฐ๋ฆฌ ๊ด‘ํ•™ ์ธํ„ฐ์ปค๋„ฅํŠธ์˜ ์ˆ˜๊ฐ€ ์ ์ฐจ ์šฐ์„ธํ•ด์งˆ ๊ฒƒ์œผ๋กœ ์˜ˆ์ƒ๋œ๋‹ค. ์ˆ˜์ง ์บ๋น„ํ‹ฐ ํ‘œ๋ฉด ๋ฐฉ์ถœ ๋ ˆ์ด์ €(VCSEL)๋Š” ์ผ๋ฐ˜์ ์œผ๋กœ ๋‹จ๊ฑฐ๋ฆฌ ์ƒํ˜ธ ์—ฐ๊ฒฐ์„ ์œ„ํ•ด ์‚ฌ์šฉ๋˜๋Š” ๊ด‘ํ•™ ๋ชจ๋“ˆ๋ ˆ์ดํ„ฐ์ด๋‹ค. VCSEL์€ ๋‚ฎ์€ ๋Œ€์—ญํญ๊ณผ ๋น„์„ ํ˜•์„ฑ์„ ๊ฐ€์ง€๊ณ  ์žˆ๊ธฐ ๋•Œ๋ฌธ์—, ๊ด‘ ์†ก์‹ ๊ธฐ๋„ ๋Œ€์—ญํญ ์ฆ๊ฐ€ ๊ธฐ์ˆ ์„ ํ•„์š”๋กœ ํ•œ๋‹ค. ๋˜ํ•œ, ๋ฐ์ดํ„ฐ ์„ผํ„ฐ์˜ ์ „๋ ฅ ์†Œ๋น„๋Š” ๊ธฐํ›„ ๋ณ€ํ™”์— ์˜ํ–ฅ์„ ๋ฏธ์น  ์ˆ˜ ์žˆ๋Š” ์šฐ๋ ค ์ง€์ ์— ๋„๋‹ฌํ–ˆ๋‹ค. ๋”ฐ๋ผ์„œ, ๋ณธ ๋…ผ๋ฌธ์€ ๋ฐ์ดํ„ฐ ์„ผํ„ฐ ์‘์šฉ์„ ์œ„ํ•œ ๊ณ ์† ์ „๋ ฅ ํšจ์œจ์ ์ธ ์†ก์‹ ๊ธฐ์— ์ดˆ์ ์„ ๋งž์ถ”๊ณ  ์žˆ๋‹ค. ํšŒ๋กœ ์„ค๊ณ„๋ฅผ ์ œ์‹œํ•˜๊ธฐ ์ „์—, ๋ถ€๋ถ„ ๊ฐ„๊ฒฉ ํ”ผ๋“œ-ํฌ์›Œ๋“œ ์ดํ€„๋ผ์ด์ € (FFE), ์˜จ์นฉ ์ „์†ก์„ ๋กœ, ์ธ๋•ํ„ฐ, T-์ฝ”์ผ๊ณผ ๊ฐ™์€ ๋Œ€์—ญํญ ํ™•์žฅ ๊ธฐ์ˆ ์„ ์ˆ˜ํ•™์ ์œผ๋กœ ๋ถ„์„ํ•œ๋‹ค. ์ฒซ ๋ฒˆ์งธ ์นฉ์€ ์ €์†ํŒŒ ์ „์†ก์„ ๋กœ๋ฅผ ๊ธฐ๋ฐ˜์œผ๋กœ ํ•œ 3-ํƒญ FFE๋ฅผ ์‚ฌ์šฉํ•˜๋Š” ์ „๋ ฅ ๋ฐ ๋ฉด์  ํšจ์œจ์ ์ธ ํŽ„์Šค-์ง„ํญ-๋ณ€์กฐ 4(PAM-4) ์†ก์‹ ๊ธฐ๋ฅผ ์ œ์‹œํ•œ๋‹ค. ๋†’์€ ํด๋Ÿญ ์ „๋ ฅ ์†Œ๋น„๋ฅผ ๊ทน๋ณตํ•˜๊ธฐ ์œ„ํ•ด ์ดํ€„๋ผ์ด์ € ํƒญ ์ƒ์„ฑ์„ ์œ„ํ•ด ์ˆ˜๋™์†Œ์ž ์ง€์—ฐ ๋ผ์ธ์„ ์ฑ„ํƒํ–ˆ๋‹ค. ์ „์†ก ๋ผ์ธ์€ ์ฐจ๋™ ๋™์ผํ‰๋ฉด๋„ํŒŒ๊ด€ ์ฃผ์œ„์— ์ด์ค‘ ํ”Œ๋กœํŒ… ๊ธˆ์† ์ฐจํ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ 15์˜ ๋†’์€ ์ „๋‹ฌ์†๋„ ๊ฐ์‡ ๋ฅผ ๋‹ฌ์„ฑํ•œ๋‹ค. ์†ก์‹ ๊ธฐ์—๋Š” 4:1 ๋ฉ€ํ‹ฐํ”Œ๋ ‰์„œ(MUX)์™€ 4-์œ„์ƒ ํด๋Ÿญ ์ƒ์„ฑ๊ธฐ๊ฐ€ ํฌํ•จ๋˜์–ด ์žˆ๋‹ค. 4:1 MUX๋Š” 2-UI ํŽ„์Šค ๋ฐœ์ƒ๊ธฐ๋ฅผ ์‚ฌ์šฉํ•˜๋ฉฐ, ์ •์„ฑ ๋ถ„์„์— ์˜ํ•ด ์ž…๋ ฅ ๊ตฌ์„ฑ์ด ๊ฒฐ์ •๋œ๋‹ค. ์ด ์นฉ์€ 65 nm CMOS ๊ธฐ์ˆ ๋กœ ์ œ์ž‘๋˜์—ˆ์œผ๋ฉฐ 0.151 mm2์˜ ๋ฉด์ ์„ ์ฐจ์ง€ํ•œ๋‹ค. ์ œ์•ˆ๋œ ์†ก์‹ ๊ธฐ ์‹œ์Šคํ…œ์€ PAM-4 ์‹ ํ˜ธ์™€ ํ•จ๊ป˜ 48 Gb/s์˜ ๋ฐ์ดํ„ฐ ์†๋„์—์„œ 3.03 pJ/b์˜ ์—๋„ˆ์ง€ ํšจ์œจ์„ ๋ณด์—ฌ์ค€๋‹ค. ๋‘ ๋ฒˆ์งธ ์นฉ์—์„œ๋Š” 3-ํƒญ FFE ๋ฐ ์—ญํšŒ์ „ T-์ฝ”์ผ์„ ์‚ฌ์šฉํ•˜๋Š” ์ „๋ ฅ ํšจ์œจ์ ์ธ PAM-4 VCSEL ์†ก์‹ ๊ธฐ๋ฅผ ์ œ์‹œํ•œ๋‹ค. ์œ„์ƒ ๋ณด๊ฐ„๊ธฐ(PI)๋Š” ๋ถ€๋ถ„ ๊ฐ„๊ฒฉ FFE ํƒญ์„ ์ƒ์„ฑํ•˜๊ณ  4-์œ„์ƒ ํด๋Ÿญ ์˜ค๋ฅ˜๋ฅผ ์ˆ˜์ •ํ•˜๋Š” ๋ฐ ์‚ฌ์šฉ๋œ๋‹ค. ์ง๋ ฌํ™” ์ „๋ ฅ ์†Œ๋น„๋ฅผ ์ค„์ด๊ธฐ ์œ„ํ•ด ์ถœ๋ ฅ ๋“œ๋ผ์ด๋ฒ„์—์„œ MSB์™€ LSB๋ฅผ ๋‘ ๊ฐœ์˜ 4:1 MUX๋ฅผ ํ†ตํ•ด ๊ฒฐํ•ฉํ•˜๋Š” ๋Œ€์‹  8:1 MUX๋ฅผ ํ†ตํ•ด PAM-4๋กœ ๊ฒฐํ•ฉํ•˜๋Š” ํšŒ๋กœ๊ฐ€ ์ œ์•ˆ๋œ๋‹ค. ๋‚ด๋ถ€ ๋ฐ ์ถœ๋ ฅ ๋…ธ๋“œ์—์„œ T-์ฝ”์ผ์€ ๋Œ€์—ญํญ์„ ์ฆ๊ฐ€์‹œํ‚ค๊ณ  ๊ธฐํ˜ธ ๊ฐ„ ๊ฐ„์„ญ(ISI)์„ ์ œ๊ฑฐํ•œ๋‹ค. ์ถœ๋ ฅ ๋„คํŠธ์›Œํฌ์—์„œ ์—ญํšŒ์ „ T-์ฝ”์ผ์€ T-์ฝ”์ผ์ด ์—†๋Š” ๊ฒฝ์šฐ๋ณด๋‹ค ๋Œ€์—ญํญ์„ 1.61๋ฐฐ ์ฆ๊ฐ€์‹œํ‚จ๋‹ค. VCSEL ๋“œ๋ผ์ด๋ฒ„๋Š” ์–‘๊ทน ๊ตฌ๋™ ๋ฐ ์ „๋ ฅ ๊ฐ์†Œ๋ฅผ ์œ„ํ•ด ๋†’์€ VSS ๋„๋ฉ”์ธ์— ๋ฐฐ์น˜๋œ๋‹ค. ์ด ์นฉ์€ 40 nm CMOS ๊ธฐ์ˆ ๋กœ ์ œ์ž‘๋˜์—ˆ๋‹ค. ์ œ์•ˆ๋œ VCSEL ์†ก์‹ ๊ธฐ๋Š” ๊ฐ๊ฐ 3.03pJ/b์™€ 2.09pJ/b์˜ ์ „๋ ฅ ํšจ์œจ๋กœ ์ตœ๋Œ€ 48Gb/s NRZ์™€ 64Gb/s PAM-4๊นŒ์ง€ ์ž‘๋™ํ•œ๋‹ค.ABSTRACT I CONTENTS III LIST OF FIGURES V LIST OF TABLES IX CHAPTER 1 INTRODUCTION 1 1.1 MOTIVATION 1 1.2 THESIS ORGANIZATION 5 CHAPTER 2 BACKGROUND OF HIGH-SPEED INTERFACE 6 2.1 OVERVIEW 6 2.2 BASIS OF DATA CENTER ARCHITECTURE 9 2.3 SHORT-REACH INTERFACE STANDARDS 12 2.4 ANALYSES OF BANDWIDTH EXTENSION TECHNIQUES 16 2.4.1 FRACTIONALLY-SPACED FFE 16 2.4.2 TRANSMISSION LINE 21 2.4.3 INDUCTOR 24 2.4.4 T-COIL 33 CHAPTER 3 DESIGN OF 48 GB/S PAM-4 ELECTRICAL TRANSMITTER IN 65 NM CMOS 43 3.1 OVERVIEW 43 3.2 FFE BASED ON DOUBLE-SHIELDED COPLANAR WAVEGUIDE 46 3.2.1 BASIC CONCEPT 46 3.2.2 PROPOSED DOUBLE-SHIELDED COPLANAR WAVEGUIDE 47 3.3 DESIGN CONSIDERATION ON 4:1 MUX 50 3.4 PROPOSED PAM-4 ELECTRICAL TRANSMITTER 53 3.5 MEASUREMENT 57 CHAPTER 4 DESIGN OF 64 GB/S PAM-4 OPTICAL TRANSMITTER IN 40 NM CMOS 64 4.1 OVERVIEW 64 4.2 DESIGN CONSIDERATION OF OPTICAL TRANSMITTER 66 4.3 PROPOSED PAM-4 VCSEL TRANSMITTER 69 4.4 MEASUREMENT 82 CHAPTER 5 CONCLUSIONS 88 BIBLIOGRAPHY 90 ์ดˆ ๋ก 101๋ฐ•

    A 5-50 Gb/s quarter rate transmitter with a 4-tap multiple-MUX based FFE in 65 nm CMOS

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    This paper presents a 5-50 Gb/s quarter-rate transmitter with a 4-tap feed-forward equalization (FFE) based on multiple-multiplexer (MUX). A bandwidth enhanced 4:1 MUX with the capability of eliminating charge-sharing effect is proposed to increase the maximum operating speed. To produce the quarter-rate parallel data streams with appropriate delays, a compact latch array associated with an interleaved-retiming technique is designed. Implemented in 65 nm CMOS technology, the transmitter occupying an area of 0.6 mm2 achieves a maximum data rate of 50 Gb/s with an energy efficiency of 3.1 pJ/bit

    A 40-Gb/s Quarter-Rate SerDes Transmitter and Receiver Chipset in 65-nm CMOS

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    This paper presents a 40-Gb/s transmitter (TX) and receiver (RX) chipset for chip-to-chip communications in a 65-nm CMOS process. The TX implements a quarter-rate multi-multiplexer (MUX)-based four-tap feed-forward equalizer (FFE), where a charge-sharing-effect elimination technique is introduced into the 4:1 MUX to optimize its jitter performance and power efficiency. The RX employs a two-stage continuous-time linear equalizer as the analog front end and integrates a low-cost sign-based zero-forcing engine relying on edge-data correlation to automatically adjust the tap weights of the TX-FFE. By embedding low-pass filters with an adaptively adjusting bandwidth into the data-sampling path and adopting high-linearity compensating phase interpolators, the clock data recovery achieves both high jitter tolerance and low jitter generation. The fabricated TX and RX chipset delivers 40-Gb/s PRBS data at BER 16-dB loss at half-baud frequency, while consuming a total power of 370 mW

    High-speed equalization and transmission in electrical interconnections

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    The relentless growth of data traffic and increasing digital signal processing capabilities of integrated circuits (IC) are demanding ever faster chip-to-chip / chip-to-module serial electrical interconnects. As data rates increase, the signal quality after transmission over printed circuit board (PCB) interconnections is severely impaired. Frequency-dependent loss and crosstalk noise lead to a reduced eye opening, a reduced signal-to-noise ratio and an increased inter-symbol interference (ISI). This, in turn, requires the use of improved signal processing or PCB materials, in order to overcome the bandwidth (BW) limitations and to improve signal integrity. By applying an optimal combination of equalizer and receiver electronics together with BW-efficient modulation schemes, the transmission rate over serial electrical interconnections can be pushed further. At the start of this research, most industrial backplane connectors, meeting the IEEE and OIF specifications such as manufactured by e.g. FCI or TE connectivity, had operational capabilities of up to 25 Gb/s. This research was mainly performed under the IWT ShortTrack project. The goal of this research was to increase the transmission speed over electrical backplanes up to 100 Gb/s per channel for next-generation telecom systems and data centers. This requirement greatly surpassed the state-ofthe-art reported in previous publications, considering e.g. 25 Gb/s duobinary and 42.8 Gb/s PAM-4 transmission over a low-loss Megtron 6 electrical backplane using off-line processing. The successful implementation of the integrated transmitter (TX) and receiver (RX) (1) , clearly shows the feasibility of single lane interconnections beyond 80 Gb/s and opens the potential of realizing industrial 100 Gb/s links using a recent IC technology process. Besides the advancement of the state-of-the-art in the field of high-speed transceivers and backplane transmission systems, which led to several academic publications, the output of this work also attracts a lot of attention from the industry, showing the potential to commercialize the developed chipset and technologies used in this research for various applications: not only in high-speed electrical transmission links, but also in high-speed opto-electronic communications such as access, active optical cables and optical backplanes. In this dissertation, the background of this research, an overview of this work and the thesis organization are illustrated in Chapter 1. In Chapter 2, a system level analysis is presented, showing that the channel losses are limiting the transmission speed over backplanes. In order to enhance the serial data rate over backplanes and to eliminate the signal degradation, several technologies are discussed, such as signal equalization and modulation techniques. First, a prototype backplane channel, from project partner FCI, implemented with improved backplane connectors is characterized. Second, an integrated transversal filter as a feed-forward equalizer (FFE) is selected to perform the signal equalization, based on a comprehensive consideration of the backplane channel performance, equalization capabilities, implementation complexity and overall power consumption. NRZ, duobinary and PAM-4 are the three most common modulation schemes for ultra-high speed electrical backplane communication. After a system-level simulation and comparison, the duobinary format is selected due to its high BW efficiency and reasonable circuit complexity. Last, different IC technology processes are compared and the ST microelectronics BiCMOS9MW process (featuring a fT value of over 200 GHz) is selected, based on a trade-off between speed and chip cost. Meanwhile it also has a benefit for providing an integrated microstrip model, which is utilized for the delay elements of the FFE. Chapter 3 illustrates the chip design of the high-speed backplane TX, consisting of a multiplexer (MUX) and a 5-tap FFE. The 4:1 MUX combines four lower rate streams into a high-speed differential NRZ signal up to 100 Gb/s as the FFE input. The 5-tap FFE is implemented with a novel topology for improved testability, such that the FFE performance can be individually characterized, in both frequency- and time-domain, which also helps to perform the coefficient optimization of the FFE. Different configurations for the gain cell in the FFE are compared. The gilbert configuration shows most advantages, in both a good high-frequency performance and an easy way to implement positive / negative amplification. The total chip, including the MUX and the FFE, consumes 750mW from a 2.5V supply and occupies an area of 4.4mm ร— 1.4 mm. In Chapter 4, the TX chip is demonstrated up to 84 Gb/s. First, the FFE performance is characterized in the frequency domain, showing that the FFE is able to work up to 84 Gb/s using duobinary formats. Second, the combination of the MUX and the FFE is tested. The equalized TX outputs are captured after different channels, for both NRZ and duobinary signaling at speeds from 64 Gb/s to 84 Gb/s. Then, by applying the duobinary RX 2, a serial electrical transmission link is demonstrated across a pair of 10 cm coax cables and across a 5 cm FX-2 differential stripline. The 5-tap FFE compensates a total loss between the TX and the RX chips of about 13.5 dB at the Nyquist frequency, while the RX receives the equalized signal and decodes the duobinary signal to 4 quarter rate NRZ streams. This shows a chip-to-chip data link with a bit error rate (BER) lower than 10โˆ’11. Last, the electrical data transmission between the TX and the RX over two commercial backplanes is demonstrated. An error-free, serial duobinary transmission across a commercial Megtron 6, 11.5 inch backplane is demonstrated at 48 Gb/s, which indicates that duobinary outperforms NRZ for attaining higher speed or longer reach backplane applications. Later on, using an ExaMAXยฎ backplane demonstrator, duobinary transmission performance is verified and the maximum allowed channel loss at 40 Gb/s transmission is explored. The eye diagram and BER measurements over a backplane channel up to 26.25 inch are performed. The results show that at 40 Gb/s, a total channel loss up to 37 dB at the Nyquist frequency allows for error-free duobinary transmission, while a total channel loss of 42 dB was overcome with a BER below 10โˆ’8. An overview of the conclusions is summarized in Chapter 5, along with some suggestions for further research in this field. (1) The duobinary receiver was developed by my colleague Timothy De Keulenaer, as described in his PhD dissertation. (2) Described in the PhD dissertation of Timothy De Keulenaer

    Design of High-Speed SerDes Transceiver for Chip-to-Chip Communications in CMOS Process

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    With the continuous increase of on-chip computation capacities and exponential growth of data-intensive applications, the high-speed data transmission through serial links has become the backbone for modern communication systems. To satisfy the massive data-exchanging requirement, the data rate of such serial links has been updated from several Gb/s to tens of Gb/s. Currently, the commercial standards such as Ethernet 400GbE, InfiniBand high data rate (HDR), and common electrical interface (CEI)-56G has been developing towards 40+ Gb/s. As the core component within these links, the transceiver chipset plays a fundamental role in balancing the operation speed, power consumption, area occupation, and operation range. Meanwhile, the CMOS process has become the dominant technology in modern transceiver chip fabrications due to its large-scale digital integration capability and aggressive pricing advantage. This research aims to explore advanced techniques that are capable of exploiting the maximum operation speed of the CMOS process, and hence provides potential solutions for 40+ Gb/s CMOS transceiver designs. The major contributions are summarized as follows. A low jitter ring-oscillator-based injection-locked clock multiplier (RILCM) with a hybrid frequency tracking loop that consists of a traditional phase-locked loop (PLL), a timing-adjusted loop, and a loop selection state-machine is implemented in 65-nm C-MOS process. In the ring voltage-controlled oscillator, a full-swing pseudo-differential delay cell is proposed to lower the device noise to phase noise conversion. To obtain high operation speed and high detection accuracy, a compact timing-adjusted phase detector tightly combined with a well-matched charge pump is designed. Meanwhile, a lock-loss detection and lock recovery is devised to endow the RILCM with a similar lock-acquisition ability as conventional PLL, thus excluding the initial frequency set- I up aid and preventing the potential lock-loss risk. The experimental results show that the figure-of-merit of the designed RILCM reaches -247.3 dB, which is better than previous RILCMs and even comparable to the large-area LC-ILCMs. The transmitter (TX) and receiver (RX) chips are separately designed and fab- ricated in 65-nm CMOS process. The transmitter chip employs a quarter-rate multi-multiplexer (MUX)-based 4-tap feed-forward equalizer (FFE) to pre-distort the output. To increase the maximum operating speed, a bandwidth-enhanced 4:1 MUX with the capability of eliminating charge-sharing effect is proposed. To produce the quarter-rate parallel data streams with appropriate delays, a compact latch array associated with an interleaved-retiming technique is designed. The receiver chip employs a two-stage continuous-time linear equalizer (CTLE) as the analog front-end and integrates an improved clock data recovery to extract the sampling clocks and retime the incoming data. To automatically balance the jitter tracking and jitter suppression, passive low-pass filters with adaptively-adjusted bandwidth are introduced into the data-sampling path. To optimize the linearity of the phase interpolation, a time-averaging-based compensating phase interpolator is proposed. For equalization, a combined TX-FFE and RX-CTLE is applied to compensate for the channel loss, where a low-cost edge-data correlation-based sign zero-forcing adaptation algorithm is proposed to automatically adjust the TX-FFEโ€™s tap weights. Measurement results show that the fabricated transmitter/receiver chipset can deliver 40 Gb/s random data at a bit error rate of 16 dB loss at the half-baud frequency, while consuming a total power of 370 mW

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ์ „๊ธฐยท์ปดํ“จํ„ฐ๊ณตํ•™๋ถ€, 2017. 2. ๊น€์žฌํ•˜.A PVT-insensitive-bandwidth PLL and a chirp frequency synthesizer PLL are proposed using a constant-relative-gain digitally-controlled oscillator (DCO), a constant-gain time-to-digital converter (TDC), and a simple digital loop filter (DLF) without an explicit calibration or additional circuit components. A digital LC-PLL that realizes a PVT-insensitive loop bandwidth (BW) by using the constant-relative-gain LC-DCO and constant-gain TDC is proposed. In other words, based on ratiometric circuit designs, the LC-DCO can make a fixed percent change to its frequency for a unit change in its digital input and the TDC can maintain a fixed range and resolution measured in reference unit intervals (UIs) across PVT variations. With such LC-DCO and TDC, the proposed PLL can realize a bandwidth which is a constant fraction of the reference frequency even with a simple proportional-integral digital loop filter without any explicit calibration loops. The prototype digital LC-PLL fabricated in a 28-nm CMOS demonstrates a frequency range of 8.38~9.34 GHz and 652-fs,rms integrated jitter from 10-kHz to 1-GHz at 8.84-GHz while dissipating 15.2-mW and occupying 0.24-mm^2. Also, the PLL across three different die samples and supply voltage ranging from 1.0 to 1.2V demonstrates a nearly constant BW at 822-kHz with the variation of ยฑ4.25-% only. A chirp frequency synthesizer PLL (FS-PLL) that is capable of precise triangular frequency modulation using type-III digital LC-PLL architecture for X-band FMCW imaging radar is proposed. By employing a phase-modulating two-point modulation (TPM), constant-gain TDC, and a simple second-order DLF with polarity-alternating frequency ramp estimator, the PLL achieves a gain self-tracking TPM realizing a frequency chirp with fast chirp slope (=chirp BW/chirp period) without increasing frequency errors around the turn-around points, degrading the effective resolution achievable. A prototype chirp FS-PLL fabricated in a 65nm CMOS demonstrates that the PLL can generate a precise triangular chirp profile centered at 8.9-GHz with 940-MHz bandwidth and 28.8-us period with only 1.9-MHz,rms frequency error including the turn-around points and 14.8-mW power dissipation. The achieved 32.63-MHz/us chirp slope is higher than that of FMCW FS-PLLs previously reported by 2.6x.CHAPTER 1 INTRODUCTION 1 1.1 MOTIVATION 1 1.2 THESIS ORGANIZATION 5 CHAPTER 2 CONVENTIONAL PHASE-LOCKED LOOP 7 2.1 CHARGE-PUMP PLL 7 2.1.1 OPERATING PRINCIPLE 7 2.1.2 LOOP DYNAMICS 9 2.2 DIGITAL PLL 10 2.2.1 OPERATING PRINCIPLE 11 2.2.2 LOOP DYNAMICS 12 CHAPTER 3 VARIATIONS ON PHASE-LOCKED LOOP 14 3.1 OSCILLATOR GAIN VARIATION 14 3.1.1 RING VOLTAGE-CONTROLLED OSCILLATOR 15 3.1.2 LC VOLTAGE-CONTROLLED OSCILLATOR 17 3.1.3 LC DIGITALLY-CONTROLLED OSCILLATOR 19 3.2 PHASE DETECTOR GAIN VARIATION 20 3.2.1 LINEAR PHASE DETECTOR 20 3.2.2 LINEAR TIME-TO-DIGITAL CONVERTER 21 CHAPTER 4 PROPOSED DCO AND TDC FOR CALIBRATION-FREE PLL 23 4.1 DIGTALLY-CONTROLLED OSCILLATOR (DCO) 25 4.1.1 OVERVIEW 24 4.1.2 CONSTANT-RELATIVE-GAIN DCO 26 4.2 TIME-TO-DIGITAL CONVERTER (TDC) 28 4.2.1 OVERVIEW 28 4.2.2 CONSTANT-GAIN TDC 30 CHAPTER 5 PVT-INSENSITIVE-BANDWIDTH PLL 35 5.1 OVERVIEW 36 5.2 PRIOR WORKS 37 5.3 PROPOSED PVT-INSENSITIVE-BANDWIDTH PLL 39 5.4 CIRCUIT IMPLEMENTATION 41 5.4.1 CAPACITOR-TUNED LC-DCO 41 5.4.2 TRANSFORMER-TUNED LC-DCO 45 5.4.3 OVERSAMPLING-BASED CONSTANT-GAIN TDC 49 5.4.4 PHASE DIGITAL-TO-ANALOG CONVERTER 52 5.4.5 DIGITAL LOOP FILTER 54 5.4.6 FREQUENCY DIVIDER 55 5.4.7 BANG-BANG PHASE-FREQUENCY DETECTOR 56 5.5 CELL-BASED DESIGN FLOW 57 5.6 MEASUREMENT RESULTS 58 CHAPTER 6 CHIRP FREQUENCY SYNTHESIZER PLL 66 6.1 OVERVIEW 67 6.2 PRIOR WORKS 71 6.3 PROPOSED CHIRP FREQUENCY SYNTHESIZER PLL 75 6.4 CIRCUIT IMPLEMENTATION 83 6.4.1 SECOND-ORDER DIGITAL LOOP FILTER 83 6.4.2 PHASE MODULATOR 84 6.4.3 CONSTANT-GAIN TDC 85 6.4.4 VRACTOR-BASED LC-DCO 87 6.4.5 OVERALL CLOCK CHAIN 90 6.5 MEASUREMENT RESULTS 91 6.6 SIGNAL-TO-NOISE RATIO OF RADAR 98 CHAPTER 7 CONCLUSION 100 BIBLIOGRAPHY 102 ์ดˆ๋ก 109Docto

    Topical Workshop on Electronics for Particle Physics

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    The purpose of the workshop was to present results and original concepts for electronics research and development relevant to particle physics experiments as well as accelerator and beam instrumentation at future facilities; to review the status of electronics for the LHC experiments; to identify and encourage common efforts for the development of electronics; and to promote information exchange and collaboration in the relevant engineering and physics communities
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