Nanometer Frequency Synthesis Beyond the Phase-Locked Loop E-Book

Liming Xiu

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: IEEE Press Series on Microelectronic Systems
• Sprache: Englisch

Seitenzahl: 433

Veröffentlichungsjahr: 2012

Beschreibung

Introducing a new, pioneering approach to integrated circuit design Nanometer Frequency Synthesis Beyond Phase-Locked Loop introduces an innovative new way of looking at frequency that promises to open new frontiers in modern integrated circuit (IC) design. While most books on frequency synthesis deal with the phase-locked loop (PLL), this book focuses on the clock signal. It revisits the concept of frequency, solves longstanding problems in on-chip clock generation, and presents a new time-based information processing approach for future chip design. Beginning with the basics, the book explains how clock signal is used in electronic applications and outlines the shortcomings of conventional frequency synthesis techniques for dealing with clock generation problems. It introduces the breakthrough concept of Time-Average-Frequency, presents the Flying-Adder circuit architecture for the implementation of this approach, and reveals a new circuit device, the Digital-to-Frequency Converter (DFC). Lastly, it builds upon these three key components to explain the use of time rather than level to represent information in signal processing. Provocative, inspiring, and chock-full of ideas for future innovations, the book features: * A new way of thinking about the fundamental concept of clock frequency * A new circuit architecture for frequency synthesis: the Flying-Adder direct period synthesis * A new electronic component: the Digital-to-Frequency Converter * A new information processing approach: time-based vs. level-based * Examples demonstrating the power of this technology to build better, cheaper, and faster systems Written with the intent of showing readers how to think outside the box, Nanometer Frequency Synthesis Beyond the Phase-Locked Loop is a must-have resource for IC design engineers and researchers as well as anyone who would like to be at the forefront of modern circuit design.

Leseprobe

Table of Contents

Cover

IEEE Press

Title page

Copyright page

PREFACE

FREQUENCY IS CHANGED

SIMPLE AND ELEGANT

TIME, NUMBER, AND THE BEAUTY OF MATHEMATICS

PLAY TIME AS WE PLAY LEVEL

CHAPTER 1 CLOCK SIGNAL IN ELECTRONIC SYSTEMS

1.1 THE SIGNIFICANCE OF CLOCK SIGNAL

1.2 THE CHARACTERISTICS OF CLOCK SIGNAL

1.3 CLOCK SIGNAL DRIVING DIGITAL SYSTEM

1.4 CLOCK SIGNAL DRIVING SAMPLING SYSTEM

1.5 EXTRACTING CLOCK SIGNAL FROM DATA: CLOCK DATA RECOVERY

1.6 CLOCK USAGE IN SYSTEM-ON-CHIP

1.7 TWO FIELDS: CLOCK GENERATION AND CLOCK DISTRIBUTION

CHAPTER 2 CLOCK GENERATION: EXISTING FREQUENCY SYNTHESIS TECHNIQUES

2.1 DIRECT ANALOG FREQUENCY SYNTHESIS

2.2 DIRECT DIGITAL FREQUENCY SYNTHESIS

2.3 INDIRECT METHOD (PHASE-LOCKED LOOP BASED)

2.4 THE SHARED GOAL: ALL CYCLES HAVE SAME LENGTH-IN-TIME

CHAPTER 3 TIME-AVERAGE-FREQUENCY

3.1 THE SCALE OF LEVEL AND THE SCALE OF TIME

3.2 WHAT IS FREQUENCY?

3.3 REINVESTIGATING THE FREQUENCY CONCEPT: THE BIRTH OF TIME-AVERAGE-FREQUENCY

3.4 TIME-AVERAGE-FREQUENCY IN CIRCUIT IMPLEMENTATION

3.5 AVERAGE FREQUENCY, TIME-AVERAGE-FREQUENCY, AND FUNDAMENTAL FREQUENCY

3.6 THE NEED OF A THEORY

3.7 THE SUMMARY: WHY DO WE NEED TIME-AVERAGE-FREQUENCY?

CHAPTER 4 FLYING-ADDER DIRECT PERIOD SYNTHESIS ARCHITECTURE

4.1 THE WORKING PRINCIPLE

4.2 THE MAJOR CHALLENGES IN THE FLYING-ADDER CIRCUIT

4.3 THE CIRCUIT OF PROOF OF CONCEPT

4.4 THE WORKING CIRCUITRY

4.5 FREQUENCY TRANSFER FUNCTION, FREQUENCY RANGE, FREQUENCY RESOLUTION, AND FREQUENCY SWITCHING SPEED

4.6 THE TECHNIQUE OF POST DIVIDER FRACTIONAL BITS RECOVERY

4.7 FLYING-ADDER PLL: FAPLL

4.8 FLYING-ADDER FRACTIONAL DIVIDER

4.9 INTEGER-FLYING-ADDER ARCHITECTURE

4.10 THE ALGORITHM TO SEARCH OPTIMUM PARAMETERS

4.11 THE CONSTRUCTION OF THE ACCUMULATOR

4.12 THE CONSTRUCTION OF THE HIGH SPEED MULTIPLEX

4.13 NON-2’S POWER FLYING-ADDER CIRCUIT

4.14 EXPANDING VCO FREQUENCY RANGE IN NANOMETER CMOS PROCESSES

4.15 MULTIPLE FLYING-ADDER SYNTHESIZERS

4.16 FLYING-ADDER IMPLEMENTATION STYLES

4.17 SIMULATION APPROACHES

4.18 THE IMPACT OF INPUT MISMATCH ON OUTPUT JITTER

4.19 FLYING-ADDER CIRCUIT AS DIGITAL CONTROLLED OSCILLATOR

4.20 FLYING-ADDER TERMINOLOGY

4.21 FLYING-ADDER SYNTHESIZER AND TIME-AVERAGE-FREQUENCY: THE EXPERIMENTAL EVIDENCE

4.22 TIME-AVERAGE-FREQUENCY AND SETUP CONSTRAINT: REVISIT

4.23 SENSE THE FREQUENCY DIFFERENCE: THE TIME-AVERAGE-FREQUENCY WAY

4.24 FLYING-ADDER AND DIRECT DIGITAL SYNTHESIS (DDS): THE DIFFERENCE

4.25 FLYING-ADDER FOR PHASE (DELAY) SYNTHESIS

4.26 FLYING-ADDER FOR DUTY CYCLE CONTROL

4.27 FLYING-ADDER SYNTHESIZER IN REDUCING THE NUMBER OF PLLS IN SOC

CHAPTER 5 DIGITAL-TO-FREQUENCY CONVERTER

5.1 TWO WAYS OF REPRESENTING INFORMATION

5.2 THE CONVERTERS FOR TRANSFORMING INFORMATION

5.3 THE TWO CORNERSTONES OF THE DIGITAL-TO-FREQUENCY CONVERTER

5.4 THE THEORETICAL FOUNDATION OF FLYING-ADDER DIGITAL-TO-FREQUENCY CONVERTER

5.5 CONVERT THE SPURIOUS ENERGY TO NOISE ENERGY

5.6 MOVE SPURS AROUND

5.7 SPREAD THE ENERGY

5.8 PERFORMANCE MERITS

CHAPTER 6 THE NEW FRONTIER IN ELECTRONIC SYSTEM DESIGN

6.1 THE CLOCKING CHALLENGES IN REALITY

6.2 FLYING-ADDER AND ITS THREE MAJOR APPLICATION AREAS

6.3 FLYING-ADDER FOR ON-CHIP FREQUENCY GENERATION

6.4 FLYING-ADDER AS ADAPTIVE CLOCK GENERATOR

6.5 FLYING-ADDER AS ON-CHIP VCXO

6.6 FLYING-ADDER FOR FRAME RATE SYNCHRONIZATION AND DISPLAY MONITOR ACCOMMODATION

6.7 FLYING-ADDER FOR FREQUENCY SYNCHRONIZATION IN DIGITAL COMMUNICATION: A PREVIEW

6.8 FLYING-ADDER FOR CLOCK DATA RECOVERY

6.9 FLYING-ADDER DLL FOR DESKEW

6.10 FLYING-ADDER FOR DIGITAL FREQUENCY-LOCKED LOOP (FLYING-ADDER DFLL)

6.11 FLYING-ADDER FOR DIGITAL PHASE-LOCKED LOOP (FLYING-ADDER DPLL)

6.12 FLYING-ADDER TECHNOLOGY FOR DYNAMIC FREQUENCY SCALING

6.13 FLYING-ADDER AS 1-BIT DDFS

6.14 FLYING-ADDER FOR SPREAD SPECTRUM CLOCKING

6.15 FLYING-ADDER FOR DRIVING SAMPLING SYSTEM

6.16 FLYING-ADDER FOR NON-UNIFORM SAMPLING

6.17 FLYING-ADDER AS DIGITAL FSK MODULATOR

6.18 FLYING-ADDER FOR PWM/PFW DC-DC POWER CONVERSION

6.19 INTEGRATE CLOCKING CHIPS INTO PROCESSING CHIPS

CHAPTER 7 LOOKING INTO FUTURE: THE ERA OF “TIME”

7.1 THE FOUR FUNDAMENTAL TECHNOLOGIES IN MODERN CHIP DESIGN

7.2 “TIME”-BASED ANALOG PROCESSING

7.3 “TIME” AND FREQUENCY: ENCODING MESSAGES THROUGH MODULATION

7.4 MANIPULATE “TIME”: THE TOOLS

7.5 IT IS TIME TO USE “TIME”

APPENDICES

APPENDIX 4.A: THE VHDL CODE FOR FLYING-ADDER SYNTHESIZER

APPENDIX 4.B: HOW CLOSE CAN IT REACH AN INTEGER?

APPENDIX 4.C: THE SEED AND SET IN INTEGER-FLYING-ADDER PLL

APPENDIX 4.D: THE NUMBER OF CARRIES FROM AN XIU-ACCUMULATOR

APPENDIX 5.A: THE FLYING-ADDER STATE MACHINE MODEL (PERL)

APPENDIX 5.B: THE FLYING-ADDER WAVEFORM GENERATOR (PERL)

APPENDIX 5.C: THE FLYING-ADDER WAVEFORM GENERATOR WITH TRIANGULAR MODULATION (PERL)

APPENDIX 5.D: THE FLYING-ADDER WAVEFORM GENERATOR WITH RANDOM MODULATION (PERL)

APPENDIX 6.A: THE FA-DCXO TANGENT LINE AND LINEARITY MEASUREMENT

Index

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Copyright © 2012 by The Institute of Electrical and Electronics Engineers, Inc.

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Library of Congress Cataloging-in-Publication Data:

Xiu, Liming.

 Nanometer frequency synthesis beyond the phase-locked loop / Liming Xiu.

p. cm.

 ISBN 978-1-118-16263-7 (cloth)

 1. Timing circuits. 2. Frequency synthesizers. 3. Very high speed integrated circuits. I. Title.

 TK7868.T5X83 2012

 621.381'32–dc23

2012001531

PREFACE

I have no special talents. I am only passionately curious.

—Albert Einstein

In the great Einstein’s view, passion, desire—and above all curiosity—are the very ignition switches to spark discovery and creation. More than two decades ago, when I was studying physics in Tsinghua University (Beijing, China), this confession seemed counterfactual. After 20 years of involvement in scientific and engineering work, it is gradually starting to make sense to me. Nowadays, there are 7 billion people living on this planet. If all the people who ever lived on Earth were included, this enormous number would be exponentially larger. Among this gigantic population there are countless gifted people who are born with talent. However, history shows that only a tiny handful of people have made paramount contributions to the understanding of the world we all live in. The force that separates these all-time greats from the exceptional group of the talented is the passion to ask what and why, sincerely and unyieldingly.

FREQUENCY IS CHANGED

I am neither the great nor the gifted. But this force of curiosity does have its hold over me. In my career as a very-large-scale integration (VLSI) circuit design professional, I have had the fortune to work in many different areas (please see my other book: VLSI Circuit Design Methodology Demystified: A Conceptual Taxonomy, 2007). This unique experience provides me with the opportunity to observe everything from a broader viewpoint, the ability to see things in the bigger picture. In the meantime, it engages my curiosity. It often drives me to challenge the conventional way of doing things. One particular example is the clock signal used in the VLSI circuit. As both a circuit level phase-locked loop (PLL) designer and a system-on-a-chip integration level PLL user, I have seen the story from both sides. I distinctly remember one afternoon in the summer of 2003, after spending a long time explaining the flying-adder architecture (invented in the late 1990s) to one of my colleagues, a question suddenly occurred to me: What is frequency? Why must all the cycles have equal lengths in time? In common sense, this question looks foolish and dangerous for anyone to ask. Curiosity about this issue has intrigued me for several years (secretly, for fear of being treated as an illiterate). In 2008, after a long period of serious investigation from both theoretical and experimental perspectives, I had built up enough nerve to formally introduce the concept of “time-average-frequency.” It removes the constraint that all clock cycles must have the same length-in-time. This seemingly ridiculous or insignificant step is a bold move philosophically. Its aim is the two long-lasting problems in this field: arbitrary frequency generation and fast response in frequency switching. It will have profound influence in VLSI circuit design since clock signal is used in every chip. Along the running history of our progressive understanding of this world, it is shown that all the great advancements originate at the concept level. The greatest example is provided by Einstein. By changing our view of the two fundamental concepts of time and space, he brought us one giant step closer to the ultimate understanding of the universe. This has forever changed the way we live. In this book, the most important message that I want to share with reader is: the concept of clock frequency is changed.

Your time is limited, so don’t waste it living someone else’s life. Don’t be trapped by dogma—which is living with the results of other people’s thinking. Don’t let the noise of others’ opinions drown out your own inner voice. And most important, have the courage to follow your heart and intuition.

—Steve Jobs

The spirit behind this excerpt from Steve Jobs’s famous speech (Stanford University, 2005) is not unfamiliar. Similar wisdom has been expressed in the past by great philosophers and pioneers. But Mr. Jobs’s testimony is more touching and real to us as individuals because he lived in our time. He noticeably changed the face of technology and the modern way of life, and he preached his passion in a way that was pleasantly contagious. During the pursuit of time-average-frequency, I sometimes felt frustrated because this new thinking contradicts conventional wisdom. On several occasions, a painful price had to be paid to uphold what I believe. Today, whenever Jobs’s remark is replayed, I feel a bit of warmth and encouragement. Looking at his journey, it is confirmed again that all the greats have their own obstacles. The key to success is not superior intellect or powerful financial muscle. Instead, it is the intrinsic drive to believe, to achieve, and to change. This book is my case of this testimony.

SIMPLE AND ELEGANT

Coupled with curiosity, the other important part of my mindset is the tenacious desire to pursue simplicity and elegance in almost everything. I admire beautiful things in life: beautiful music, beautiful art, beautiful literature, beautiful sportsmanship, a beautiful soul—the list goes on and on. During the creation of the flying-adder circuit, simplicity drove me to search unrelentingly for the simplest structure that required the minimum number of transistors possible. Elegance compelled me to ensure that there is a sophisticated and yet beautiful mechanism behind the simple circuit. I am a passionate believer of the “Principle of Least Action” (Pierre-Louis Maupertuis, 1774). I apply it to my circuit design whenever I can. I hope that I can convey this attitude to readers throughout this book.

TIME, NUMBER, AND THE BEAUTY OF MATHEMATICS

The key focus of this book—frequency—is closely related to the thing that we called time. Time is a major subject of religion, philosophy, and science. Among great thinkers, there are two distinct standpoints on time. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. The opposing view is that time does not refer to any kind of physical container that events and objects move through. Instead, time is part of a fundamental intellectual structure (made of space, number, and time) within which humans sequence and compare events. In this second view, time is a virtual subject, neither an event nor a thing, and thus is not itself measurable.

Another mysterious product from human brain is the number. The world is virtually made of numbers. Numbers were invented to fulfill the need to organize our life quantitatively, beyond just qualitatively. It is generally believed that this is one of the major reasons why humans and all other species have followed different evolutionary paths (language is among the others). In our daily life, time and number are connected though an entity called the atomic clock: the definition of second. In VLSI circuit design, time and number are related by a special signal called clock. In this engineering practice, how­ever, the relationship between time (frequency) and number has not reached the harmonization achieved in our daily life. In this book, one of the goals is to see if something can be done to improve the situation (digital-to-frequency converter, the counterpart of digital-to-analog Converter). In this effort, two important mathematical tools are used: Number Theory and Fourier Analysis. During this process of reasoning and learning from several “beautiful minds,” I am amazed at the power and the striking beauty of mathematics. I am deeply touched by the mysterious harmony rooted in our number system. In this book, I want to share this joy with reader.

PLAY TIME AS WE PLAY LEVEL

The entire VLSI circuit design business is built on the fact that we use level (voltage or current level) to represent information. In analog processing, level is organized in multiple elevations. In the digital domain, it is in binary fashion. As process technology advances, some momentous changes emerge: the transistor is switching faster and faster, and the supply voltage is reduced lower and lower. Consequently, time (or rate-of-switching) becomes an attractive option to represent information. This will unquestionably influence the way that we design circuits. In this book, a million-dollar question is asked: “Can we play time as we play level?”

This book is organized in the following way:

Chapter 1 discusses how the clock signal is used in all electronic applications. The aim of this chapter is to understand our targeting problem in depth. Chapter 2 briefly reviews the existing clock generation techniques. This chapter focuses on the explanation of how this problem is conventionally dealt with. Chapter 3 looks at the root of the clock problem. It investigates the very concept of frequency and introduces the breakthrough viewpoint that leads us on an entirely new path. Chapter 4 presents the supporting technology, flying-adder architecture, which implements this new concept into circuitry. This is the hardware implementation of this novel approach introduced in chapter three. Based on the time-average-frequency concept and the flying-adder circuit, Chapter 5 coins a new device: the digital-to-frequency converter. Chapter 6 shows some examples of using this innovative technology to build cheaper, faster, and better systems. It illustrates the strength of this new technology. Chapter 7 is the visionary discussion of using “time” for signal processing. It brings forth new directions for future chip design. Its goal is to inspire the next generation researcher and engineer with new opportunities.

This book was inspired by Stay Hungry, Stay Foolish, which I second from the bottom of my heart. This mindset is the invisible hand that has created our magnificent civilization out of the void. It will serve as the lighthouse to guide us in the journey of seeking the ultimate paradise. It is my wish that this book can play a role in achieving the goal of designing “cheaper, faster, and better” electronic products that will ultimately make for a more enjoyable life.

I would like to thank my dear wife, Zhihong You, for supporting me in the completion of this book. Without her selfless effort, this book would never have been published. She has always stood beside me through both “thick and thin.” As a fellow professional who works in similar area and was trained in the same schools, her gifted mental might is highly respected by me. Fortunately, it appears that her exceptional competence has been passed to our lovely daughters Katherine and Helen. I also want to thank Katherine Xiu for helping me in English proofreading and in creating the index.

LIMING XIU

CHAPTER 1

CLOCK SIGNAL IN ELECTRONIC SYSTEMS

1.1 THE SIGNIFICANCE OF CLOCK SIGNAL

1.1.1 Clock Signal

In modern electronic-driven society, our everyday lives are supported by various kinds of electronic devices. At home, TV, computer, audio system, game machine, and digital camera are indispensable for our entertainment and relaxation. Away from home, mobile phones keep us connected with the world all the time. On the road, automobiles and airplanes with countless built-in electronic devices make them safe to be driven/flown and comfortable to ride in. At work, we spend most of our time dealing with the computer, fax machine, copier, printer, projector, etc. Without these electronic devices, people’s lives would be totally different; human society would regress many years in standard of living. Electronic devices have already penetrated into all aspects of our lives.

When in operation, almost all electronic devices rely on a very important signal: the clock. This is simply due to the fact that electronic devices are made of very-large-scale-integration (VLSI) chips, which are primarily designed on the synchronous principle. For any chip, simple or complex, its designed functionality is achieved by millions of events that occur inside it. These events do not happen randomly but in a predetermined, orderly sequence. The clock signal is the conductor of the orchestra to produce harmony. For successful operation in a large chip, many clock signals (as many as hundreds) could be required simultaneously. Usually, phase-locked loop (PLL) is used on-chip to generate these crucial clock signals. If a VLSI chip could be treated as a person and the on-chip processor were regarded as the brain, then the clock pulse is the heartbeat, the clock signal is the blood, and the clock distribution network (clock tree) is the vessel. This analogy is graphically demonstrated in Fig. 1.1.

Fig. 1.1. The importance of clock pulses: they are the heartbeats.

In the field of VLSI circuit design, the clock signal is an electrical pulse train of square waveform as shown in Fig. 1.2. It has two distinguishable voltage levels: high and low. The basic unit in this pulse train comprises one occurrence of high level voltage and one occurrence of low level voltage. The transitions between the low-to-high and high-to-low are termed the clock edges. They are called “rising edge” and “falling edge,” respectively. The length-in-time used by this basic unit is defined as the clock period; its inversion is the frequency that is often used by people to gauge the working speed of an electronic device.

Fig. 1.2. Clock signal is an electrical pulse train.

One of the most important characteristics of the clock signal is that the basic unit, often called the cycle, has to be able to repeat itself indefinitely. In other words, in this pulse train, every cycle has to be exactly the same. This is because that clock signal is the driver of the chip. The billions of operations (can also be viewed as events) inside a VLSI chip are all coordinated by clock signal. Structurally, the circuit inside the chip is designed in such way that these operations are triggered by either the rising edge or the falling edge, or both, of the clock signal. Therefore, it is essential that the occurrences of these edges in time are precisely predictable. The easiest way of achieving this goal is to make every cycle the same. A clock signal with this predictability in its waveform has enabled an important VLSI circuit design method: synchronous design. The synchronous design methodology is a milestone technology that allows the VLSI chip design industry to make great strides.