High-Speed Circuit Board Signal Integrity (Artech House Microwave Library)

As circuit boards are increasingly required to transmit signals at higher and higher speeds, signal and power integrity become increasingly crucial. Rules of thumb that you have used over and over again to prevent signal loss no longer apply to these new, high-speed, high-density circuit designs. This leading-edge circuit design resource offers you the knowledge needed to quickly pinpoint transmission problems that can compromise your entire circuit design. Discussing both design and debug issues at gigabit per second data rates, the book serves as a practical reference for your projects involving high-speed serial signaling on printed circuit boards.Step-by-step, this book goes from reviewing the essentials of linear circuit theory, to examining practical issues of pulse propagation along lossless and lossy transmission lines. It provides detailed guidelines for crosstalk, attenuation, power supply decoupling, and layer stackup tradeoffs (including pad/antipad tradeoffs). Other key topics include the construction of etched conductors, analysis of return paths and split planes, microstrip and stripline characteristics, and SMT capacitors. Filled with on-the-job-proven examples, this hands-on reference is the book that you can turn to time and again to design out and troubleshoot circuit signal loss and impedance problems. Team DDU High-Speed Circuit Board Signal Integrity 1 Cover 1 Contents 8 Preface 14 CHAPTER 1 Characteristics and Construction of Printed Wiring Boards 16 1.1 Introduction 16 1.2 Unit System 16 1.3 PWB Construction 17 1.3.1 Resins 18 1.3.2 Alternate Resin Systems 18 1.3.3 Reinforcements 20 1.3.4 Variability in Building Stackups 21 1.3.5 Mixing Laminate Types 22 1.4 PWB Traces 22 1.4.1 Copper Cladding 23 1.4.2 Copper Weights and Thickness 24 1.4.3 Plating the Surface Traces 24 1.4.4 Trace Etch Shape Effects 24 1.5 Vias 25 1.5.1 Via Aspect Ratio 28 1.6 Surface Finishes and Solder Mask 29 1.7 Summary 29 References 30 CHAPTER 2 Resistance of Etched Conductors 32 2.1 Introduction 32 2.2 Resistance at Low Frequencies 32 2.3 Loop Resistance and the Proximity Effect 35 2.3.1 Resistance Matrix 36 2.3.2 Proximity Effect 37 2.4 Resistance Increase with Frequency: Skin Effect 39 2.5 Hand Calculations of Frequency-Dependent Resistance 42 2.5.1 Return Path Resistance 43 2.5.2 Conductor Resistance 43 2.5.3 Total Loop Resistance 44 2.6 Resistance Increase Due to Surface Roughness 44 2.7 Summary 45 References 45 CHAPTER 3 Capacitance of Etched Conductors 46 3.1 Introduction 46 3.2 Capacitance and Charge 46 3.2.1 Dielectric Constant 47 3.3 Parallel Plate Capacitor 48 3.4 Self and Mutual Capacitance 50 3.5 Capacitance Matrix 52 3.6 Dielectric Losses 54 3.6.1 Reactance and Displacement Current 55 3.6.2 Loss Tangent 55 3.6.3 Calculating Loss Tangent and Conductance G 56 3.7 Environmental Effects on Laminate εr and Loss Tangent 58 3.7.1 Temperature Effects 59 3.7.2 Moisture Effects 59 3.8 Summary 60 References 60 CHAPTER 4 Inductance of Etched Conductors 62 4.1 Introduction 62 4.2 Field Theory 62 4.2.1 Permeability 63 4.2.2 Inductance 63 4.2.3 Internal and External Inductance 64 4.2.4 Partial Inductance 64 4.2.5 Reciprocity Principal and Transverse Electromagnetic Mode 65 4.3 Circuit Behavior of Inductance 66 4.3.1 Inductive Voltage Drop 68 4.3.2 Inductive Reactance 69 4.4 Inductance Matrix 70 4.4.1 Using the Reciprocity Principle to Obtain the Inductance Matrix from a Capacitance Matrix 70 4.5 Mutual Inductance 70 4.5.1 Coupling Coefficient 71 4.5.2 Beneficial Effects of Mutual Inductance 72 4.5.3 Deleterious Effects of Mutual Inductance 74 4.6 Hand Calculations for Inductance 75 4.6.1 Inductance of a Wire Above a Return Plane 75 4.6.2 Inductance of Side-by-Side Wires 76 4.6.3 Inductance of Parallel Plates 76 4.6.4 Inductance of Microstrip 78 4.6.5 Inductance of Stripline 78 4.7 Summary 79 References 80 CHAPTER 5 Transmission Lines 82 5.1 Introduction 82 5.2 General Circuit Model of a Lossy Transmission Line 82 5.2.1 Relationship Between ωL andR 85 5.2.2 Relationship Between ωC and G 85 5.3 Impedance 86 5.3.1 Calculating Impedance 87 5.4 Traveling Waves 88 5.4.1 Propagation Constant 89 5.4.2 Phase Shift, Delay, and Wavelength 90 5.4.3 Phase Constant at High Frequencies When R and G Are Small 93 5.4.4 Attenuation 94 5.4.5 Neper and Decibel Conversion 95 5.5 Summary and Worked Examples 97 References 101 CHAPTER 6 Return Paths and Power Supply Decoupling 102 6.1 Introduction 102 6.2 Proper Return Paths 102 6.2.1 Return Paths of Ground-Referenced Signals 104 6.2.2 Stripline 105 6.3 Stripline Routed Between Power and Ground Planes 105 6.3.1 When Power Plane Voltage Is the Same as Signal Voltage 105 6.3.2 When Power Plane Voltage Differs from Signal Voltage 108 6.3.3 Power System Inductance 109 6.4 Split Planes, Motes, and Layer Changes 110 6.4.1 Motes 110 6.4.2 Layer Changes 113 6.5 Connectors and Dense Pin Fields 113 6.5.1 Plane Perforation 114 6.5.2 Antipads 114 6.5.3 Nonfunctional Pads 117 6.5.4 Guidelines for Routing Through Dense Pin Fields 118 6.6 Power Supply Bypass/Decoupling Capacitance 120 6.6.1 Power Supply Integrity 121 6.6.2 Distributed Power Supply Interconnect Model 125 6.7 Connecting to Decoupling Capacitors 127 6.7.1 Via Inductance 127 6.8 Summary 129 References 130 CHAPTER 7 Serial Communication, Loss, and Equalization 132 7.1 Introduction 132 7.2 Harmonic Contents of a Data Stream 132 7.2.1 Line Spectra 134 7.2.2 Combining Harmonics to Create a Pulse 135 7.2.3 The Fourier Integral 137 7.2.4 Rectangular Pulses with Nonzero Rise Times 138 7.3 Line Codes 140 7.4 Bit Rate and Data Rate 141 7.5 Block Codes Used in Serial Transmission 143 7.6 ISI 145 7.6.1 Dispersion 145 7.6.2 Lone 1-Bit Pattern 146 7.7 Eye Diagrams 147 7.8 Equalization and Preemphasis 149 7.8.1 Preemphasis 149 7.8.2 Passive Equalizers 152 7.8.3 Passive RC Equalizer 154 7.9 DC-Blocking Capacitors 155 7.9.1 Calculating the Coupling Capacitor Value 157 7.10 Summary 160 References 161 CHAPTER 8 Single-Ended and Differential Signaling and Crosstalk 164 8.1 Introduction 164 8.2 Odd and Even Modes 164 8.2.1 Circuit Description of Odd and Even Modes 165 8.2.2 Coupling Coefficient 168 8.2.3 Stripline and Microstrip Odd- and Even-Mode Timing 170 8.2.4 Effects of Spacing on Impedance 172 8.3 Multiconductor Transmission Lines 173 8.3.1 Bus Segmentation for Simulation Purposes 174 8.3.2 Switching Behavior of a Wide Bus 175 8.3.3 Simulation Results for Loosely Coupled Lines 176 8.3.4 Simulation Results for Tightly Coupled Lines 177 8.3.5 Data-Dependent Timing Jitter in Multiconductor Transmission Lines 179 8.4 Differential Signaling, Termination, and Layout Rules 180 8.4.1 Differential Signals and Noise Rejection 180 8.4.2 Differential Impedance and Termination 181 8.4.3 Reflection Coefficient and Return Loss 185 8.4.4 PWB Layout Rules When Routing Differential Pairs 187 8.5 Crosstalk 188 8.5.1 Coupled-Line Circuit Model 190 8.5.2 NEXT and FEXT Coupling Factors 192 8.5.3 Using Kb to Predict NEXT 193 8.5.4 Using Kf to Predict FEXT 194 8.5.5 Guard Traces 194 8.5.6 Crosstalk Worked Example 195 8.5.7 Crosstalk Summary 197 8.6 Summary 197 References 198 CHAPTER 9 Characteristics of Printed Wiring Stripline and Microstrips 200 9.1 Introduction 200 9.2 Stripline 200 9.2.1 Time of Flight 201 9.2.2 Impedance Relationship Between Trace Width, Thickness, and Plate Spacing 202 9.2.3 Mask Biasing to Obtain a Specific Impedance 204 9.2.4 Hand Calculation of Zo 204 9.2.5 Stripline Fabrication 206 9.3 Microstrip 208 9.3.1 Exposed Microstrip 209 9.3.2 Solder Mask and Embedded Microstrip 211 9.4 Losses in Stripline and Microstrip 212 9.4.1 Dielectric Loss 214 9.4.2 Conductor Loss 214 9.5 Microstrip and Stripline Differential Pairs 216 9.5.1 Broadside Coupled Stripline 216 9.5.2 Edge-Coupled Stripline 219 9.5.3 Edge-Coupled Microstrip 220 9.6 Summary 221 References 222 CHAPTER 10 Surface Mount Capacitors 224 10.1 Introduction 224 10.2 Ceramic Surface Mount Capacitors 224 10.2.1 Dielectric Temperature Characteristics Classification 224 10.2.2 Body Size Coding 226 10.2.3 Frequency Response 227 10.2.4 Inductive Effects: ESL 229 10.2.5 Dielectric and Conductor Losses: ESR 230 10.2.6 Leakage Currents: Insulation Resistance 233 10.2.7 Electrical Model 234 10.2.8 MLCC Capacitor Aging 235 10.2.9 Capacitance Change with DC Bias and Frequency 236 10.2.10 MLCC Usage Guidelines 237 10.3 SMT Tantalum Capacitors 238 10.3.1 Body Size Coding 238 10.3.2 Frequency Response 239 10.3.3 Electrical Model 240 10.3.4 Aging 240 10.3.5 Effects of DC Bias, Temperature, and Relative Humidity 240 10.3.6 Failure of Tantalum Capacitors 241 10.3.7 ESR and Self Heating: Voltage and Temperature Derating 242 10.3.8 Usage Guidelines 242 10.4 Replacing Tantalum with High-Valued Ceramic Capacitors 243 References 245 Appendix: Conversion Factors 246 About the Author 248 Index 250 Team DDU 1 Team DDU......Page 1 Contents......Page 8 Preface......Page 14 1.2 Unit System......Page 16 1.3 PWB Construction......Page 17 1.3.2 Alternate Resin Systems......Page 18 1.3.3 Reinforcements......Page 20 1.3.4 Variability in Building Stackups......Page 21 1.4 PWB Traces......Page 22 1.4.1 Copper Cladding......Page 23 1.4.4 Trace Etch Shape Effects......Page 24 1.5 Vias......Page 25 1.5.1 Via Aspect Ratio......Page 28 1.7 Summary......Page 29 References......Page 30 2.2 Resistance at Low Frequencies......Page 32 2.3 Loop Resistance and the Proximity Effect......Page 35 2.3.1 Resistance Matrix......Page 36 2.3.2 Proximity Effect......Page 37 2.4 Resistance Increase with Frequency: Skin Effect......Page 39 2.5 Hand Calculations of Frequency-Dependent Resistance......Page 42 2.5.2 Conductor Resistance......Page 43 2.6 Resistance Increase Due to Surface Roughness......Page 44 References......Page 45 3.2 Capacitance and Charge......Page 46 3.2.1 Dielectric Constant......Page 47 3.3 Parallel Plate Capacitor......Page 48 3.4 Self and Mutual Capacitance......Page 50 3.5 Capacitance Matrix......Page 52 3.6 Dielectric Losses......Page 54 3.6.2 Loss Tangent......Page 55 3.6.3 Calculating Loss Tangent and Conductance G......Page 56 3.7 Environmental Effects on Laminate εr and Loss Tangent......Page 58 3.7.2 Moisture Effects......Page 59 References......Page 60 4.2 Field Theory......Page 62 4.2.2 Inductance......Page 63 4.2.4 Partial Inductance......Page 64 4.2.5 Reciprocity Principal and Transverse Electromagnetic Mode......Page 65 4.3 Circuit Behavior of Inductance......Page 66 4.3.1 Inductive Voltage Drop......Page 68 4.3.2 Inductive Reactance......Page 69 4.5 Mutual Inductance......Page 70 4.5.1 Coupling Coefficient......Page 71 4.5.2 Beneficial Effects of Mutual Inductance......Page 72 4.5.3 Deleterious Effects of Mutual Inductance......Page 74 4.6.1 Inductance of a Wire Above a Return Plane......Page 75 4.6.3 Inductance of Parallel Plates......Page 76 4.6.5 Inductance of Stripline......Page 78 4.7 Summary......Page 79 References......Page 80 5.2 General Circuit Model of a Lossy Transmission Line......Page 82 5.2.2 Relationship Between ωC and G......Page 85 5.3 Impedance......Page 86 5.3.1 Calculating Impedance......Page 87 5.4 Traveling Waves......Page 88 5.4.1 Propagation Constant......Page 89 5.4.2 Phase Shift, Delay, and Wavelength......Page 90 5.4.3 Phase Constant at High Frequencies When R and G Are Small......Page 93 5.4.4 Attenuation......Page 94 5.4.5 Neper and Decibel Conversion......Page 95 5.5 Summary and Worked Examples......Page 97 References......Page 101 6.2 Proper Return Paths......Page 102 6.2.1 Return Paths of Ground-Referenced Signals......Page 104 6.3.1 When Power Plane Voltage Is the Same as Signal Voltage......Page 105 6.3.2 When Power Plane Voltage Differs from Signal Voltage......Page 108 6.3.3 Power System Inductance......Page 109 6.4.1 Motes......Page 110 6.5 Connectors and Dense Pin Fields......Page 113 6.5.2 Antipads......Page 114 6.5.3 Nonfunctional Pads......Page 117 6.5.4 Guidelines for Routing Through Dense Pin Fields......Page 118 6.6 Power Supply Bypass/Decoupling Capacitance......Page 120 6.6.1 Power Supply Integrity......Page 121 6.6.2 Distributed Power Supply Interconnect Model......Page 125 6.7.1 Via Inductance......Page 127 6.8 Summary......Page 129 References......Page 130 7.2 Harmonic Contents of a Data Stream......Page 132 7.2.1 Line Spectra......Page 134 7.2.2 Combining Harmonics to Create a Pulse......Page 135 7.2.3 The Fourier Integral......Page 137 7.2.4 Rectangular Pulses with Nonzero Rise Times......Page 138 7.3 Line Codes......Page 140 7.4 Bit Rate and Data Rate......Page 141 7.5 Block Codes Used in Serial Transmission......Page 143 7.6.1 Dispersion......Page 145 7.6.2 Lone 1-Bit Pattern......Page 146 7.7 Eye Diagrams......Page 147 7.8.1 Preemphasis......Page 149 7.8.2 Passive Equalizers......Page 152 7.8.3 Passive RC Equalizer......Page 154 7.9 DC-Blocking Capacitors......Page 155 7.9.1 Calculating the Coupling Capacitor Value......Page 157 7.10 Summary......Page 160 References......Page 161 8.2 Odd and Even Modes......Page 164 8.2.1 Circuit Description of Odd and Even Modes......Page 165 8.2.2 Coupling Coefficient......Page 168 8.2.3 Stripline and Microstrip Odd- and Even-Mode Timing......Page 170 8.2.4 Effects of Spacing on Impedance......Page 172 8.3 Multiconductor Transmission Lines......Page 173 8.3.1 Bus Segmentation for Simulation Purposes......Page 174 8.3.2 Switching Behavior of a Wide Bus......Page 175 8.3.3 Simulation Results for Loosely Coupled Lines......Page 176 8.3.4 Simulation Results for Tightly Coupled Lines......Page 177 8.3.5 Data-Dependent Timing Jitter in Multiconductor Transmission Lines......Page 179 8.4.1 Differential Signals and Noise Rejection......Page 180 8.4.2 Differential Impedance and Termination......Page 181 8.4.3 Reflection Coefficient and Return Loss......Page 185 8.4.4 PWB Layout Rules When Routing Differential Pairs......Page 187 8.5 Crosstalk......Page 188 8.5.1 Coupled-Line Circuit Model......Page 190 8.5.2 NEXT and FEXT Coupling Factors......Page 192 8.5.3 Using Kb to Predict NEXT......Page 193 8.5.5 Guard Traces......Page 194 8.5.6 Crosstalk Worked Example......Page 195 8.6 Summary......Page 197 References......Page 198 9.2 Stripline......Page 200 9.2.1 Time of Flight......Page 201 9.2.2 Impedance Relationship Between Trace Width, Thickness, and Plate Spacing......Page 202 9.2.4 Hand Calculation of Zo......Page 204 9.2.5 Stripline Fabrication......Page 206 9.3 Microstrip......Page 208 9.3.1 Exposed Microstrip......Page 209 9.3.2 Solder Mask and Embedded Microstrip......Page 211 9.4 Losses in Stripline and Microstrip......Page 212 9.4.2 Conductor Loss......Page 214 9.5.1 Broadside Coupled Stripline......Page 216 9.5.2 Edge-Coupled Stripline......Page 219 9.5.3 Edge-Coupled Microstrip......Page 220 9.6 Summary......Page 221 References......Page 222 10.2.1 Dielectric Temperature Characteristics Classification......Page 224 10.2.2 Body Size Coding......Page 226 10.2.3 Frequency Response......Page 227 10.2.4 Inductive Effects: ESL......Page 229 10.2.5 Dielectric and Conductor Losses: ESR......Page 230 10.2.6 Leakage Currents: Insulation Resistance......Page 233 10.2.7 Electrical Model......Page 234 10.2.8 MLCC Capacitor Aging......Page 235 10.2.9 Capacitance Change with DC Bias and Frequency......Page 236 10.2.10 MLCC Usage Guidelines......Page 237 10.3.1 Body Size Coding......Page 238 10.3.2 Frequency Response......Page 239 10.3.5 Effects of DC Bias, Temperature, and Relative Humidity......Page 240 10.3.6 Failure of Tantalum Capacitors......Page 241 10.3.8 Usage Guidelines......Page 242 10.4 Replacing Tantalum with High-Valued Ceramic Capacitors......Page 243 References......Page 245 Appendix: Conversion Factors......Page 246 About the Author......Page 248 Index......Page 250 Discussing both design and debugging issues at gigabit-per-second data rates, this book serves as a practical reference for projects involving high-speed serial signaling on printed wiring boards. Formulas, terminology, and a refresher on basic electrostatic and electromagnetic principals will be useful for signal integrity engineers. High-speed circuit designers will find an entry into the electromagnetics and physics of high-speed signaling. The book introduces concepts fundamental to high-speed signaling, such as lossy transmission line behavior, skin effect, and characteristics of laminates. Focus is on the effects of dielectric and conductor loss on signal quality, with particular emphasis on serial differential signaling. Thierauf is a scientist in the private sector. Annotation ©2004 Book News, Inc., Portland, OR This circuit design cookbook is the answer for electronic engineers who must quickly find out why their circuit designs are losing signals. The author uses his award-winning expertise to give practitioners the essentials they need to know about signal and power integrity. (Midwest) This engineering reference book covers the theoretical and practical aspects of high-speed digital signalling at the level of the printed circuit board.