Signal and Power Integrity - Simplified

Good Approximation for the Resistance of Interconnects 115 4.3 Bulk Resistivity 118 4.4 Resistance per Length 119 4.5 Sheet Resistance 121 4.6 The Bottom Line 124 Chapter 5: The Physical Basis of Capacitance 127 5.1 Current Flow in Capacitors 128 5.2 The Capacitance of a Sphere 130 5.3 Parallel Plate Approximation 131 5.4 Dielectric Constant 133 5.5 Power and Ground Planes and Decoupling Capacitance 135 5.6 Capacitance per Length 138 5.7 2D Field Solvers 143 5.8 Effective Dielectric Constant 146 5.9 The Bottom Line 150 Chapter 6: The Physical Basis of Inductance 151 6.1 What Is Inductance? 151 6.2 Inductance Principle #1: There Are Circular Rings of Magnetic-Field Lines Around All Currents 152 6.3 Inductance Principle #2: Inductance Is the Number of Webers of Field Line Rings Around a Conductor per Amp of Current Through It 154 6.4 Self-Inductance and Mutual Inductance 156 6.5 Inductance Principle #3: When the Number of Field Line Rings Around a Conductor Changes, There Will Be a Voltage Induced Across the Ends of the Conductor 158 6.6 Partial Inductance 161 6.7 Effective, Total, or Net Inductance and Ground Bounce 167 6.8 Loop Self- and Mutual Inductance 173 6.9 The Power-Distribution Network (PDN) and Loop Inductance 178 6.10 Loop Inductance per Square of Planes 183 6.11 Loop Inductance of Planes and Via Contacts 184 6.12 Loop Inductance of Planes with a Field of Clearance Holes 187 6.13 Loop Mutual Inductance 188 6.14 Equivalent Inductance of Multiple Inductors 189 6.15 Summary of Inductance 191 6.16 Current Distributions and Skin Depth 193 6.17 High-Permeability Materials 202 6.18 Eddy Currents 204 6.19 The Bottom Line 206 Chapter 7: The Physical Basis of Transmission Lines 209 7.1 Forget the Word Ground 210 7.2 The Signal 211 7.3 Uniform Transmission Lines 212 7.4 The Speed of Electrons in Copper 214 7.5 The Speed of a Signal in a Transmission Line 215 7.6 Spatial Extent of the Leading Edge 219 7.7 "Be the Signal" 220 7.8 The Instantaneous Impedance of a Transmission Line 224 7.9 Characteristic Impedance and Controlled Impedance 227 7.10 Famous Characteristic Impedances 230 7.11 The Impedance of a Transmission Line 233 7.12 Driving a Transmission Line 238 7.13 Return Paths 241 7.14 When Return Paths Switch Reference Planes 244 7.15 A First-Order Model of a Transmission Line 257 7.16 Calculating Characteristic Impedance with Approximations 262 7.17 Calculating the Characteristic Impedance with a 2D Field Solver 265 7.18 An n-Section Lumped Circuit Model 270 7.19 Frequency Variation of the Characteristic Impedance 278 7.20 The Bottom Line 279 Chapter 8: Transmission Lines and Reflections 281 8.1 Reflections at Impedance Changes 282 8.2 Why Are There Reflections? 284 8.3 Reflections from Resistive Loads 288 8.4 Source Impedance 290 8.5 Bounce Diagrams 292 8.6 Simulating Reflected Waveforms 295 8.7 Measuring Reflections with a TDR 295 8.8 Transmission Lines and Unintentional Discontinuities 299 8.9 When to Terminate 301 8.10 The Most Common Termination Strategy for Point-to-Point Topology 304 8.11 Reflections from Short Series Transmission Lines 306 8.12 Reflections from Short-Stub Transmission Lines 309 8.13 Reflections from Capacitive End Terminations 311 8.14 Reflections from Capacitive Loads in the Middle of a Trace 314 8.15 Capacitive Delay Adders 317 8.16 Effects of Corners and Vias 319 8.17 Loaded Lines 325 8.18 Reflections from Inductive Discontinuities 327 8.19 Compensation 331 8.20 The Bottom Line 334 Chapter 9: Lossy Lines, Rise-Time Degradation, and Material Properties 337 9.1 Why Worry About Lossy Lines? 338 9.2 Losses in Transmission Lines 340 9.3 Sources of Loss: Conductor Resistance and Skin Depth 342 9.4 Sources of Loss: The Dielectric 346 9.5 Dissipation Factor 351 9.6 The Real Meaning of Dissipation Factor 354 9.7 Modeling Lossy Transmission Lines 360 9.8 Characteristic Impedance of a Lossy Transmission Line 367 9.9 Signal Velocity in a Lossy Transmission Line 369 9.10 Attenuation and the dB 371 9.11 Attenuation in Lossy Lines 376 9.12 Measured Properties of a Lossy Line in the Frequency Domain 385 9.13 The Bandwidth of an Interconnect 390 9.14 Time-Domain Behavior of Lossy Lines 397 9.15 Improving the Eye Diagram of a Transmission Line 400 9.16 Pre-emphasis and Equalization 402 9.17 The Bottom Line 403 Chapter 10: Cross Talk in Transmission Lines 405 10.1 Superposition 406 10.2 Origin of Coupling: Capacitance and Inductance 407 10.3 Cross Talk in Transmission Lines: NEXT and FEXT 409 10.4 Describing Cross Talk 411 10.5 The SPICE Capacitance Matrix 413 10.6 The Maxwell Capacitance Matrix and 2D Field Solvers 417 10.7 The Inductance Matrix 424 10.8 Cross Talk in Uniform Transmission Lines and Saturation Length 425 10.9 Capacitively Coupled Currents 431 10.10 Inductively Coupled Currents 435 10.11 Near-End Cross Talk 438 10.12 Far-End Cross Talk 441 10.13 Decreasing Far-End Cross Talk 448 10.14 Simulating Cross Talk 451 10.15 Guard Traces 457 10.16 Cross Talk and Dielectric Constant 464 10.17 Cross Talk and Timing 466 10.18 Switching Noise 469 10.19 Summary of Reducing Cross Talk 473 10.20 The Bottom Line 474 Chapter 11: Differential Pairs and Differential Impedance 475 11.1 Differential Signaling 476 11.2 A Differential Pair 480 11.3 Differential Impedance with No Coupling 482 11.4 The Impact from Coupling 486 11.5 Calculating Differential Impedance 493 11.6 The Return-Current Distribution in a Differential Pair 496 11.7 Odd and Even Modes 502 11.8 Differential Impedance and Odd-Mode Impedance 507 11.9 Common Impedance and Even-Mode Impedance 508 11.10 Differential and Common Signals and Odd- and Even-Mode Voltage Components 511 11.11 Velocity of Each Mode and Far-End Cross Talk 513 11.12 Ideal Coupled Transmission-Line Model or an Ideal Differential Pair 519 11.13 Measuring Even- and Odd-Mode Impedance 520 11.14 Terminating Differential and Common Signals 522 11.15 Conversion of Differential to Common Signals 529 11.16 EMI and Common Signals 534 11.17 Cross Talk in Differential Pairs 539 11.18 Crossing a Gap in the Return Path 542 11.19 To Tightly Couple or Not to Tightly Couple 544 11.20 Calculating Odd and Even Modes from Capacitance- and Inductance-Matrix Elements 546 11.21 The Characteristic Impedance Matrix 550 11.22 The Bottom Line 553 Chapter 12: S-Parameters for Signal Integrity Applications 555 12.1 S-Parameters, the New Universal Metric 555 12.2 What Are S-Parameters? 557 12.3 Basic S-Parameter Formalism 559 12.4 S-Parameter Matrix Elements 562 12.5 Simulating Return and Insertion Loss 567 12.6 A Transparent Interconnect 570 12.7 Changing the Port Impedance 573 12.8 The Phase of S21 for a Uniform 50-Ohm Transmission Line 574 12.9 The Magnitude of S21 for a Uniform Transmission Line 577 12.10 Coupling to Other Transmission Lines 582 12.11 Insertion Loss for Non-50-Ohm Transmission Lines 589 12.12 Data-Mining S-Parameters 594 12.13 Single-Ended and Differential S-Parameters 596 12.14 Differential Insertion Loss 601 12.15 The Mode Conversion Terms 605 12.16 Converting to Mixed-Mode S-Parameters 607 12.17 Time and Frequency Domains 609 12.18 The Bottom Line 613 Chapter 13: The Power Distribution Network (PDN) 615 13.1 The Problem 615 13.2 The Root Cause 618 13.3 The Most Important Design Guidelines for the PDN 620 13.4 Establishing the Target Impedance Is Hard 621 13.5 Every Product Has a Unique PDN Requirement 629 13.6 Engineering the PDN 631 13.7 The VRM 633 13.8 Simulating Impedance with SPICE 635 13.9 On-die Capacitance 637 13.10 The Package Barrier 639 13.11 The PDN with No Decoupling Capacitors 644 13.12 The MLCC Capacitor 646 13.13 The Equivalent Series Inductance 650 13.14 Approximating Loop Inductance 652 13.15 Optimizing the Mounting of Capacitors 661 13.16 Combining Capacitors in Parallel 667 13.17 Engineering a Reduced Parallel Resonant Peak by Adding More Capacitors 673 13.18 Selecting Capacitor Values 675 13.19 Estimating the Number of Capacitors Needed 681 13.20 How Much Does a nH Cost? 683 13.21 Quantity or Specific Values? 687 13.22 Sculpting the Impedance Profiles: The Frequency Domain Target Impedance (FDTI) Method 692 13.23 When Every pH Counts 699 13.24 Location, Location, Location 703 13.25 When Spreading Inductance Is the Limitation 707 13.26 The Chip View 710 13.27 Bringing It All Together 713 13.28 The Bottom Line 717 Appendix A: 100 General Design Guidelines to Minimize Signal-Integrity Problems 719 Appendix B: 100 Collected Rules of Thumb to Help Estimate Signal-Integrity Effects 727 Appendix C: Selected References 739 Index 741