A Baker's Dozen: Real Analog Solutions for Digital Designers

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Название: A Baker's Dozen: Real Analog Solutions for Digital Designers

Автор: Bonnie Baker

Издательство: Newnes

Год: 2005

Страниц: 362

ISBN: 0-7506-7819-4

Формат: PDF

Размер: 10 Mб

Язык: English

This book has been written to help digital engineers who need a few basic analog tools in their toolbox. For practicing digital engineers, students, educators and hands-on managers who are looking for the analog foundation they need to handle their daily engineering problems, this will serve as a valuable reference to the nuts-and-bolts of system analog design in a digital world.

This book is a hands-on designer's guide to the most important topics in analog electronicssuch as Analog-to-Digital and Digital-to-Analog conversion, operational amplifiers, filters, and integrating analog and digital systems. The presentation is tailored for engineers who are primarily experienced and/or educated in digital circuit design. This book will teach such readers how to "think analog" when it is the best solution to their problem. Special attention is also given to fundamental topics, such as noise and how to use analog test and measurement equipment, that are often ignored in other analog titles aimed at professional engineers.

* Extensive use of case-histories and real design examples.

* Offers digital designers the right analog "tool" for the job at hand.

* Conversational, annecdotal "tone" is very easily accessible by students and practitioners alike.

Contents

Preface .....................................................................................................ix

Acknowledgments ......................................................................................xi

About the Author .................................................................................... xiii

Chapter 1: Bridging the Gap Between Analog and Digital .............................. 1

Try to Measure Temperature Digitally ....................................................................................... 6

Road Blocks Abound ................................................................................................................. 8

The Ultimate Key to Analog Success ...................................................................................... 14

How Analog and Digital Design Differ ................................................................................... 15

Time and Its Inversion .............................................................................................................. 20

Organizing Your Toolbox ......................................................................................................... 21

Set Your Foundation and Move On, Out of the Box ................................................................ 22

Chapter 1 References ............................................................................................................... 23

Chapter 2: The Basics Behind Analog-to-Digital Converters .......................... 25

The Key Specifications of Your ADC ...................................................................................... 28

Successive Approximation Register (SAR) Converters ........................................................... 40

Sigma-Delta (Σ−Δ) Converters ................................................................................................ 46

Conclusion ............................................................................................................................... 59

Chapter 2 References ............................................................................................................... 60

Chapter 3: The Right ADC for the Right Application ................................... 63

Classes of Input Signals .......................................................................................................... 65

Using an RTD for Temperature Sensing: SAR Converter or Sigma-Delta Solution? ............. 72

RTD Signal Conditioning Path Using the Sigma-Delta ADC ................................................ 76

Measuring Pressure: SAR Converter or Sigma-Delta Solution? ............................................. 77

The Pressure Sensor Signal Conditioning Path Using a SAR ADC ....................................... 79

Pressure Sensor Signal Conditioning Path Using a Sigma-Delta ADC ................................... 80

Photodiode Applications .......................................................................................................... 81

Photosensing Signal Conditioning Path Using a SAR ADC ................................................... 81

Photosensing Signal Conditioning Path Using a Sigma-Delta ADC ....................................... 82

Motor Control Solutions .......................................................................................................... 83

Conclusion .............................................................................................................................. 88

Chapter 3 References ............................................................................................................... 89

Chapter 4: Do I Filter Now, Later or Never? ............................................... 91

Key Low-Pass Analog Filter Design Parameters ..................................................................... 95

Anti-Aliasing Filter Theory ................................................................................................... 103

Analog Filter Realization ....................................................................................................... 105

How to Pick Your Operational Amplifier ............................................................................... 108

Anti-Aliasing Filters for Near DC Analog Signals ................................................................ 109

Multiplexed Systems .............................................................................................................. 112

Continuous Analog Signals .................................................................................................... 114

Matching the Anti-Aliasing Filter to the System ................................................................... 115

Chapter 4 References ............................................................................................................. 116

Chapter 5: Finding the Perfect Op Amp for Your Perfect Circuit ................. 117

Choose the Technology Wisely .............................................................................................. 121

Fundamental Operational Amplifier Circuits ......................................................................... 122

Using these Fundamentals ..................................................................................................... 129

Amplifier Design Pitfalls ....................................................................................................... 131

Chapter 5 References ............................................................................................................. 133

Chapter 6: Putting the Amp Into a Linear System ...................................... 135

The Basics of Amplifier DC Operation .................................................................................. 137

Every Amplifier is Waiting to Oscillate, and Every Oscillator is

Waiting to Amplify ............................................................................................................. 151

Determining System Stability ............................................................................................... 157

Time Domain Performance .................................................................................................... 161

Go Forth ............................................................................................................................... 163

Chapter 6 References ............................................................................................................. 164

Chapter 7: SPICE of Life ........................................................................ 165

The Old Pencil and Paper Design Process ............................................................................. 172

Is Your Simulation Fundamentally Valid? .............................................................................. 175

Macromodels: What Can They Do? ...................................................................................... 179

Concluding Remarks .............................................................................................................. 183

Chapter 7 References ............................................................................................................. 184

Chapter 8: Working the Analog Problem From the Digital Domain ............. 185

Pulse Width Modulators (PWM) Used as a Digital-to-Analog Converter ............................. 188

Using the Comparator for Analog Conversions ..................................................................... 194

Window Comparator .............................................................................................................. 196

Combining the Comparator with a Timer .............................................................................. 197

Using the Timer and Comparator to Build a Sigma-Delta A/D Converter ........................... 199

Conclusion ............................................................................................................................. 207

Chapter 8 References ............................................................................................................. 208

Chapter 9: Systems Where Analog and Digital Work Together ................... 209

Selecting the Right Battery Chemistry for Your Application ................................................. 212

Taking the Battery Voltage to a Useful System Voltage ......................................................... 213

Defining Power Supply Efficiency ........................................................................................ 214

Comparing The Three Power Devices ................................................................................... 219

What is the Best Solution for Battery-Operated Systems? .................................................... 221

Designing Low-Power Microcontroller Systems is a State of Mind ..................................... 222

Conclusion ............................................................................................................................. 228

Chapter 9 References ............................................................................................................. 229

Chapter 10: Noise – The Three Categories: Device, Conducted and Emitted .. 231

Definitions of Noise Specifications and Terms ...................................................................... 234

Device Noise ......................................................................................................................... 238

Conducted Noise .................................................................................................................... 254

Chapter 10 References ........................................................................................................... 260

Chapter 11: Layout/Grounding (Precision, High Speed and Digital) ............ 261

The Similarities of Analog and Digital Layout Practices ...................................................... 263

Where the Domains Differ – Ground Planes Can Be a Problem .......................................... 266

Where the Board and Component Parasitics Can Do the Most Damage ............................... 267

Layout Techniques That Improve ADC Accuracy and Resolution ....................................... 274

The Art of Laying Out Two-Layer Boards ............................................................................ 277

Current Return Paths With or Without a Ground Plane ......................................................... 281

Layout Tricks for a 12-Bit Sensing System ........................................................................... 282

General Layout Guidelines – Device Placement ................................................................... 284

General Layout Guidelines – Ground and Power Supply Strategy ....................................... 284

Signal Traces .......................................................................................................................... 287

Did I Say Bypass and Use an Anti-Aliasing Filter? ............................................................... 287

Bypass Capacitors .................................................................................................................. 287

Anti-Aliasing Filters .............................................................................................................. 288

PCB Design Checklist ........................................................................................................... 288

Chapter 11 References ........................................................................................................... 290

Chapter 12: The Trouble With Troubleshooting Your Mixed-Signal Designs

Without the Right Tools ....................................................................... 291

The Basic Tools for Your Troubleshooting Arsenal ............................................................... 293

You ask, “Does my Circuit A/D Converter Work?” ............................................................... 295

Power Supply Noise ............................................................................................................... 298

Improper Use of Amplifiers ................................................................................................... 301

Don’t Miss the Details ........................................................................................................... 303

Conclusion ............................................................................................................................. 305

Chapter 12 References ........................................................................................................... 306

Chapter 13: Combining Digital and Analog in the Same Engineer, and on the

Same Board ........................................................................................ 307

The Signal Chain to the Real World ...................................................................................... 309

Tools of the Trade .................................................................................................................. 310

Throwing the Digital In With the Analog .............................................................................. 314

Conclusion ............................................................................................................................. 318

Appendix A: Analog-to-Digital Converter Specification Definitions

and Formulas ...................................................................................... 319

Appendix B: Reading FFTs ...................................................................... 329

Reading the FFT Plot ............................................................................................................. 331

Appendix C: Op Amp Specification Definitions and Formulas ...................... 337

Index .................................................................................................... 343