EMC on Printed Circuit Board

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EMC on Printed Circuit Board
C 00/Montrose F ront Page v Thursday, January 4. 6: 54PM T Maralena, and Matthew 00/MontroseFront Page vii Thursday, January 4, 1996 6: 54 PM Contents Preface Acknowledgments Chapter 1-Introduction Fundamental Definitions EMC and the Printed Circuit board North American regulatory Requirements .8 Worldwide Regulatory Requirements Additional north american regulatory requirements ..13 Supplemental Information 14 Reference Chapter 2-Printed circuit board basics 号号··鲁鲁 Layer Stackup Assignment 17 Two-layer boards 17 Four-lay 20 Six-layer boards 22 Eight-layer boards Ten-layer board 20-H Rule 26 Grounding methods 28 Single-point grounding 28 multipoint grounding Ground and signal loops(Excluding eddy currents) Image planes 34 Partiti Logic familie 41 00/MontroseFront Page viii Thursday, January 4, 1996 6: 54 PM /elocity of Propagation Critical Frequencies(7/20) References 45 Chapter3 Bypassing and decoupling..…∴∴∴ 47 Resonance 48 Capacitor physical characteristics 50 Capacitor Value Selection Parallel Capacitors 56 Power and Ground Plane capacitance Capacitor Lead Length Inductance Placement 61 Power planes 61 Capacitors Bulk capacitors 65 Chapter 4-Clock Circuits 69 Placement 70 Localized ground planes 71 Impedance Control..... Propagation Delay 76 Capacitive loadi Decoupling....... 80 Trace Lengths 8 Impedance matching-Reflections 82 Calculating Trace Lengths 84 86 Loaded Stripline Routing layers... 89 Routin ng layers 91 Layer jumping use of vias.......... Guard/Shunt traces Crosstalk 100 Trace Termination Calculating Decoupling Capacitor values 108 Components 111 Trace Separation and the 3-w rule 112 Reference 115 Chapter 5-Interconnects and 1/o ...,,,117 Partitioning ........118 Functional subsystems 118 Quiet areas l19 Internal radiated noise coupling 120 00/MontroseFront Page ix Thursday, January 4, 1996 6: 54 PM Contents Isolation and Partitioning(moating) 121 Method 1: Isolation in moating 121 Method 2: Bridge in a moat--partitioning 122 Filtering and grounding 126 filtering 126 Grounding(I/O connector) 131 Local area Network I/O Layout 137 140 Energy Hazard protection(Fusing) 142 Creepage and clearance Distances 144 Referencc 145 Chapter 6--Electrostatic Discharge Protection 147 B .147 Chapter7— Backpla Id daughter cards 157 Basics 157 60 and 100 I trace impedance examples Traces and partitions 158 160 Backplane Construction l61 B: BasIcs 161 167 Number of connector slots 168 Interconnects 168 Mechanical Signal routing ...170 Trace Length/Signal Termination 171 Crosstalk 171 Ground Loop o 172 d Slots in backplane 17 Chapter8 Additional Design Techniques..…….…...l77 Trace Routing for 177 How to Select a Ferrite Device 179 Grounded heatsinks 182 Lithium Battery Circuits 187 BNC Connectors 187 Fil 189 Appendix a: Summary of design Techniques∴∴……195 Printed Circuit board B Bypassing and Decoupling 197 00/MontroseFront Page x Thursday, January 4. 1996 6: 54 PM x Contents Clocks 198 Interconnects and 1/0 202 Electrostatic Discharge Protection 204 Backplanes and Daughter Cards Additional design Techniques 208 Appendix b: International EMI Specification Limits∴∴∴∴∴…∴∴2ll Definition of Classification levels FCC/DOC Emission limits 212 International Emission Limits Summary(Sample list) 216 Bibliography 223 Index 227 00/MontroseFront Page xi Thursday, January 4, 1996 6: 54 PM Preface This design guide is presented to assist in printed circuit board design and layout, with the intent of meeting North American and international EMC compliance requirements. Many different layout design methodologies exist. This technical guide illustrates generally applicable layout methods for EMC compliance. Implementation of these methods may vary for a particular printed circuit board design he intended audience for this guide is engineers who design elec tronic products that use printed circuit boards. These engineers may focus on analog, digital, or system-level boards Regardless of their specialties, all engineers must produce a design that is suitable for actual production. Frequently, more emphasis is placed on functionality of the design than on overall system integration. System integration is usually assigned to product engineers, mechanical engi- neers, or others within the organization. Design engineers must now con sider other aspects of product design, including the layout and production of printed circuit boards for EMC, which includes cognizance of the man ner in which the electromagnetic fields transfer from the circuit boards to the chassis and/or case structure Not only must a design work properly, it must also comply with inter- national regulatory requirements Engineers who specialize in regulatory issues must evaluate products based on different standards. This guide presents techniques that will alleviate existing conflicts among various layout methods a great deal of technical information related to printed circuit board design and layout is available commercially as well as from public domain documents. Typically, these sources provide only a brief discus 00/MontroseFront Page xii Thursday, January 4, 1996 6: 54 PM xii Prefa sion on how to implement a layout technique to solve an EMI problem (selected S listed in the Bibliography) The guide itself is derived from lecture notes used to present EMC and printed circuit board layout information to engineers. The principles should prove useful for engineers in a variety of functions, including elec trical and mechanical design, Cad/Cae, engineering and production test, manufacturing, and other fields 00/MontroseFront Page xiii Thursday, January 4, 1996 6: 54 PM Acknowledgments Thanks to William (Bill) Kimmel and Daryl Gerke of Kimmel Gerke Associates, Ltd, St. Paul, Minnesota; Todd Hubing, University of Mis souri;and Doug Smith, at&t Bell Laboratories who provided technical review of the material for content and accuracy in addition to pointing out different aspects of printed circuit board design techniques not covered in my earlier drafts A special acknowledgment is given to Mr. W. Michael King of Costa Mesa, California, for his expertise, technical review, friendship, and encouragement without which I would never have achieved the technical knowledge to write this book. My very special acknowledgment is to my wife, Margaret, and my two children, Maralena and matthew, who tolerated my late night work and long hours at the keyboard. Without their understanding and support, this book could never have been written Mark l. montrose Santa clara, California

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