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Principles of Power Integrity for PDN Design--Simplified

Principles of Power Integrity for PDN Design--Simplified

Robust and Cost Effective Design for High Speed Digital Products

Larry Smith, Eric Bogatin

Mar 2017, Hardback, 816 pages
ISBN13: 9780132735551
ISBN10: 0132735555
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Consistently Design PDNs That Deliver Reliable Performance at the Right Cost

Too often, PDN designs work inconsistently, and techniques that work in some scenarios seem to fail inexplicably in others. This book explains why and presents realistic processes for getting PDN designs right in any new product. Drawing on 60+ years of signal and power integrity experience, Larry Smith and Eric Bogatin show how to manage noise and electrical performance, and complement intuition with analysis to balance cost, performance, risk, and schedule. Throughout, they distill the essence of complex real-world problems, quantify core principles via approximation, and apply them to specific examples. For easy usage, dozens of key concepts and observations are highlighted as tips and listed in quick, chapter-ending summaries.

Coverage includes
• A practical, start-to-finish approach to consistently meeting PDN performance goals
• Understanding how signals interact with interconnects
• Identifying root causes of common problems, so you can avoid them
• Leveraging analysis tools to efficiently explore design space and optimize tradeoffs
• Analyzing impedance-related properties of series and parallel RLC circuits
• Measuring low impedance for components and entire PDN ecologies
• Predicting loop inductance from physical design features
• Reducing peak impedances from combinations of capacitors
• Understanding power and ground plane properties in the PDN interconnect
• Taming signal integrity problems when signals change return planes
• Reducing peak impedance created by on-die capacitance and package lead inductance
• Controlling transient current waveform interactions with PDN features
• Simple spreadsheet-based analysis techniques for quickly creating first-pass designs

This guide will be indispensable for all engineers involved in PDN design, including product, board, and chip designers; system, hardware, component, and package engineers; power supply designers, SI and EMI engineers, sales engineers, and their managers.

Preface xix
Acknowledgments xxvii
About the Authors xxix
Chapter 1 Engineering the Power Delivery Network 1
1.1 What Is the Power Delivery Network (PDN) and Why Should I Care? 1
1.2 Engineering the PDN 5
1.3 “Working” or “Robust” PDN Design 8
1.4 Sculpting the PDN Impedance Profile 12
1.5 The Bottom Line 14
Reference 15
Chapter 2 Essential Principles of Impedance for PDN Design 17
2.1 Why Do We Care About Impedance? 17
2.2 Impedance in the Frequency Domain 18
2.3 Calculating or Simulating Impedance 21
2.4 Real Circuit Components vs Ideal Circuit Elements 26
2.5 The Series RLC Circuit 30
2.6 The Parallel RLC Circuit 34
2.7 The Resonant Properties of a Series and Parallel RLC Circuit 36
2.8 Examples of RLC Circuits and Real Capacitors 42
2.9 The PDN as Viewed by the Chip or by the Board 46
2.10 Transient Response 52
2.11 Advanced Topic: The Impedance Matrix 56
2.12 The Bottom Line 66
References 68
Chapter 3 Measuring Low Impedance 69
3.1 Why Do We Care About Measuring Low Impedance? 69
3.2 Measurements Based on the V/I Definition of Impedance 70
3.3 Measuring Impedance Based on the Reflection of Signals 71
3.4 Measuring Impedance with a VNA 76
3.5 Example: Measuring the Impedance of Two Leads in a DIP 81
3.6 Example: Measuring the Impedance of a Small Wire Loop 86
3.7 Limitations of VNA Impedance Measurements at Low Frequency 89
3.8 The Four-Point Kelvin Resistance Measurement Technique 93
3.9 The Two-Port Low Impedance Measurement Technique 95
3.10 Example: Measuring the Impedance of a 1-inch Diameter Copper Loop 102
3.11 Accounting for Fixture Artifacts 105
3.12 Example: Measured Inductance of a Via 109
3.13 Example: Small MLCC Capacitor on a Board 114
3.14 Advanced Topic: Measuring On-Die Capacitance 120
3.15 The Bottom Line 134
References 136
Chapter 4 Inductance and PDN Design 137
4.1 Why Do We Care About Inductance in PDN Design? 137
4.2 A Brief Review of Capacitance to Put Inductance in Perspective 138
4.3 What Is Inductance? Essential Principles of Magnetic Fields and Inductance 141
4.4 Impedance of an Inductor 147
4.5 The Quasi-Static Approximation for Inductance 150
4.6 Magnetic Field Density, B 155
4.7 Inductance and Energy in the Magnetic Field 159
4.8 Maxwell’s Equations and Loop Inductance 163
4.9 Internal and External Inductance and Skin Depth 167
4.10 Loop and Partial, Self- and Mutual Inductance 172
4.11 Uniform Round Conductors 175
4.12 Approximations for the Loop Inductance of Round Loops 179
4.13 Loop Inductance of Wide Conductors Close Together 182
4.14 Approximations for the Loop Inductance of Any Uniform Transmission Line 188
4.15 A Simple Rule of Thumb for Loop Inductance 194
4.16 Advanced Topic: Extracting Loop Inductance from the S-parameters Calculated with a 3D Field Solver 195
4.17 The Bottom Line 202
References 204
Chapter 5 Practical Multi-Layer Ceramic Chip Capacitor Integration 205
5.1 Why Use Capacitors? 205
5.2 Equivalent Circuit Models for Real Capacitors 206
5.3 Combining Multiple Identical Capacitors in Parallel 209
5.4 The Parallel Resonance Frequency Between Two Different Capacitors 211
5.5 The Peak Impedance at the PRF 215
5.6 Engineering the Capacitance of a Capacitor 220
5.7 Capacitor Temperature and Voltage Stability 222
5.8 How Much Capacitance Is Enough? 225
5.9 The ESR of Real Capacitors: First- and Second-Order Models 229
5.10 Estimating the ESR of Capacitors from Spec Sheets 234
5.11 Controlled ESR Capacitors 238
5.12 Mounting Inductance of a Capacitor 240
5.13 Using Vendor-Supplied S-parameter Capacitor Models 251
5.14 How to Analyze Vendor-Supplied S-Parameter Models 254
5.15 Advanced Topics: A Higher Bandwidth Capacitor Model 258
5.16 The Bottom Line 272
References 274
Chapter 6 Properties of Planes and Capacitors 275
6.1 The Key Role of Planes 275
6.2 Low-Frequency Property of Planes: Parallel Plate Capacitance 278
6.3 Low-Frequency Property of Planes: Fringe Field Capacitance 279
6.4 Low-Frequency Property of Planes: Fringe Field Capacitance in Power Puddles 285
6.5 Loop Inductance of Long, Narrow Cavities 290
6.6 Spreading Inductance in Wide Cavities 292
6.7 Extracting Spreading Inductance from a 3D Field Solver 304
6.8 Lumped-Circuit Series and Parallel Self-Resonant Frequency 307
6.9 Exploring the Features of the Series LC Resonance 312
6.10 Spreading Inductance and Source Contact Location 315
6.11 Spreading Inductance Between Two Contact Points 317
6.12 The Interactions of a Capacitor and Cavities 325
6.13 The Role of Spreading Inductance: When Does Capacitor Location Matter? 327
6.14 Saturating the Spreading Inductance 332
6.15 Cavity Modal Resonances and Transmission Line Properties 334
6.16 Input Impedance of a Transmission Line and Modal Resonances 340
6.17 Modal Resonances and Attenuation 343
6.18 Cavity Modes in Two Dimensions 347
6.19 Advanced Topic: Using Transfer Impedance to Probe Spreading Inductance 354
6.20 The Bottom Line 361
References 362
Chapter 7 Taming Signal Integrity Problems When Signals Change Return Planes 363
7.1 Signal Integrity and Planes 363
7.2 Why the Peak Impedances Matter 364
7.3 Reducing Cavity Noise through Lower Impedance and Higher Damping 367
7.4 Suppressing Cavity Resonances with Shorting Vias 372
7.5 Suppressing Cavity Resonances with Many DC Blocking Capacitors 383
7.6 Estimating the Number of DC Blocking Capacitors to Suppress Cavity Resonances 387
7.7 Determining How Many DC Blocking Capacitors Are Needed to Carry Return Current 393
7.8 Cavity Impedance with a Suboptimal Number of DC Blocking Capacitors 397
7.9 Spreading Inductance and Capacitor Mounting Inductance 401
7.10 Using Damping to Suppress Parallel Resonant Peaks Created by a Few Capacitors 403
7.11 Cavity Losses and Impedance Peak Reduction 408
7.12 Using Multiple Capacitor Values to Suppress Impedance Peak 411
7.13 Using Controlled ESR Capacitors to Reduce Peak Impedance Heights 414
7.14 Summary of the Most Important Design Principles for Managing Return Planes 418
7.15 Advanced Topic: Modeling Planes with Transmission Line Circuits 419
7.16 The Bottom Line 423
References 425
Chapter 8 The PDN Ecology 427
8.1 Putting the Elements Together: The PDN Ecology and the Frequency Domain 428
8.2 At the High-Frequency End: The On-Die Decoupling Capacitance 430
8.3 The Package PDN 440
8.4 The Bandini Mountain 447
8.5 Estimating the Typical Bandini Mountain Frequency 452
8.6 Intrinsic Damping of the Bandini Mountain 456
8.7 The Power Ground Planes with Multiple Via Pair Contacts 460
8.8 Looking from the Chip Through the Package into the PCB Cavity 465
8.9 Role of the Cavity: Small Boards, Large Boards, and “Power Puddles” 469
8.10 At the Low Frequency: The VRM and Its Bulk Capacitor 476
8.11 Bulk Capacitors: How Much Capacitance Is Enough? 479
8.12 Optimizing the Bulk Capacitor and VRM 483
8.13 Building the PDN Ecosystem: The VRM, Bulk Capacitor, Cavity, Package, and On-Die Capacitance 488
8.14 The Fundamental Limits to the Peak Impedance 492
8.15 Using One Value MLCC Capacitor on the Board-General Features 498
8.16 Optimizing the Single MLCC Capacitance Value 502
8.17 Using Three Different Values of MLCC Capacitors on the Board 507
8.18 Optimizing the Values of Three Capacitors 511
8.19 The Frequency Domain Target Impedance Method (FDTIM) for Selecting Capacitor Values and the Minimum Number of Capacitors 514
8.20 Selecting Capacitor Values with the FDTIM 516
8.21 When the On-Die Capacitance Is Large and Package Lead Inductance Is Small 521
8.22 An Alternative Decoupling Strategy Using Controlled ESR Capacitors 527
8.23 On-Package Decoupling (OPD) Capacitors 532
8.24 Advanced Section: Impact of Multiple Chips on the Board Sharing the Same Rail 540
8.25 The Bottom Line 543
References 545
Chapter 9 Transient Currents and PDN Voltage Noise 547
9.1 What’s So Important About the Transient Current? 547
9.2 A Flat Impedance Profile, a Transient Current, and a Target Impedance 550
9.3 Estimating the Transient Current to Calculate the Target Impedance with a Flat Impedance Profile 552
9.4 The Actual PDN Current Profile Through a Die 553
9.5 Clock-Edge Current When Capacitance Is Referenced to Both Vss and Vdd 558
9.6 Measurement Example: Embedded Controller Processor 562
9.7 The Real Origin of PDN Noise—How Clock-Edge Current Drives PDN Noise 565
9.8 Equations That Govern a PDN Impedance Peak 572
9.9 The Most Important Current Waveforms That Characterize the PDN 577
9.10 PDN Response to an Impulse of Dynamic Current 579
9.11 PDN Response to a Step Change in Dynamic Current 582
9.12 PDN Response to a Square Wave of Dynamic Current at Resonance 585
9.13 Target Impedance and the Transient and AC Steady-State Responses 589
9.14 Impact of Reactive Elements, q-Factor, and Peak Impedances on PDN Voltage Noise 595
9.15 Rogue Waves 602
9.16 A Robust Design Strategy in the Presence of Rogue Waves 610
9.17 Clock-Edge Current Impulses from Switched Capacitor Loads 613
9.18 Transient Current Waveforms Composed of a Series of Clock Impulses 622
9.19 Advanced Section: Applying Clock Gating, Clock Swallowing, and Power Gating to Real CMOS Situations 629
9.20 Advanced Section: Power Gating 633
9.21 The Bottom Line 638
References 640
Chapter 10 Putting It All Together: A Practical Approach to PDN Design 643
10.1 Reiterating Our Goal in PDN Design 643
10.2 Summary of the Most Important Power Integrity Principles 645
10.3 Introducing a Spreadsheet to Explore Design Space 654
10.4 Lines 1-12: PDN Input Voltage, Current, and Target Impedance Parameters 658
10.5 Lines 13-24: 0th Dip (Clock-Edge) Noise and On-Die Parameters 661
10.6 Extracting the Mounting Inductance and Resistance 665
10.7 Analyzing Typical Board and Package Geometries for Inductance 674
10.8 The Three Loops of the PDN Resonance Calculator (PRC) Spreadsheet 677
10.9 The Performance Figures of Merit 682
10.10 Significance of Damping and q-factors 685
10.11 Using a Switched Capacitor Load Model to Stimulate the PDN 694
10.12 Impulse, Step, and Resonance Response for Three-Peak PDN: Correlation to Transient Simulation 696
10.13 Individual q-factors in Both the Frequency and Time Domains 703
10.14 Rise Time and Stimulation of Impedance Peak 710
10.15 Improvements for a Three-Peak PDN: Reduced Loop Inductance of the Bandini Mountain and Selective MLCC Capacitor Values 718
10.16 Improvements for a Three-Peak PDN: A Better SMPS Model 722
10.17 Improvements for a Three-Peak PDN: On-Package Decoupling (OPD) Capacitors 724
10.18 Transient Response of the PDN: Before and After Improvement 731
10.19 Re-examining Transient Current Assumptions 736
10.20 Practical Limitations: Risk, Performance, and Cost Tradeoffs 739
10.21 Reverse Engineering the PDN Features from Measurements 740
10.22 Simulation-to-Measurement Correlation 747
10.23 Summary of the Simulated and Measured PDN Impedance and Voltage Features 754
10.24 The Bottom Line 757
References 759
Index 761


  • Master PDN design techniques that work all the time at the lowest cost
  • By two of the world's leading experts in power delivery network design: Larry Smith and Eric Bogatin
  • Simplifies and clarifies the essential principles that underlie PDN performance, and helps you strengthen your practical engineering intuition in these areas
  • Demonstrates a simplified approach to analysis that helps you make better component selection and design decisions

Larry D. Smith is a Principal Power Integrity Engineer at Qualcomm. Prior to joining Qualcomm in 2011, he worked at Altera from 2005 to 2011 and Sun Microsystems from 1996 to 2005, where he did development work in the field of signal and power integrity. Before this, he worked at IBM in the areas of reliability, characterization, failure analysis, power supply and analog circuit design, packaging, and signal integrity. Mr. Smith received the BSEE degree from Rose-Hulman Institute of Technology and the MS degree in material science from the University of Vermont. He has more than a dozen patents and has authored numerous journal and conference papers.

Eric Bogatin is currently the Dean of the Teledyne LeCroy Signal Integrity Academy, at www.beTheSignal.com, an Adjunct Professor at the University of Colorado-Boulder in the ECEE department, and editor of the Signal Integrity Journal (www .SignalIntegrityJournal.com). Bogatin received his BS in physics from MIT and MS, and PhD in physics from the University of Arizona in Tucson. He has held senior engineering and management positions at Bell Labs, Raychem, Sun Microsystems, Ansoft, and Interconnect Devices. He has written six technical books in the field and presented classes and lectures on signal integrity worldwide. In 2011, his company Bogatin Enterprises, which he founded with his wife Susan in 1990, was acquired by Teledyne LeCroy. After concluding his live public classes in 2013, he devoted his efforts into creating the Signal Integrity Academy, a web portal to provide all of his classes and training content online for individuals and for companies. In addition to lecturing and writing on signal and power integrity topics, Bogatin also writes science fiction novels. The first in a series, Shadow Engineer, was published in 2016.