Pcb Design for Real-World Emi Control

by Archambeault, Bruce R.

• ISBN13: 9781402071300
• ISBN10: 1402071302
• eBook ISBN(s): 9781475736403
• Format: Hardcover
• Copyright: 2002-08-01
• Publisher: Kluwer Academic Pub
• More Book Details
• Purchase Benefits

Summary

PCB Design for Real-World EMI Control is intended for EMC designers and electronic design engineers. It emphasizes understanding basic concepts of controlling the currents on printed circuit boards (pcb's), and provides a wealth of insightful information detailing the possible sources of emissions. Numerous design strategies are presented to help readers understand how to produce, control and eliminate emission sources.Additional highlights include the following:-Information explaining how to design pcb's to pass EMC Requirements the first time! -Controlling intentional and unintentional currents at their source; -Decoupling strategies explained and myths exposed; -Proper I/O filter design and connection strategy explained; -Not simply a list of do's and don't's....but an explanation of "why" things work as they do; -"Ground is a place where potatoes and carrots grow!" -Basic shielding design considerations for PCBs included, and more.This 'hands-on' book will help designers understand "why" or "why not" to implement a specific design practice. PCB Design for Real-World EMI Control will be an invaluable resource for the pcb designer.

Table of Contents

Introduction to EMI/EMC Design for Printed Circuit Boards	1	(8)
Introduction to EMI/EMC	1	(3)
EMI Emissions Sources	4	(1)
Inductance	5	(1)
``Ground''	6	(1)
Shielding	6	(1)
Summary	7	(2)
EMC Fundamentals	9	(16)
Introduction	9	(1)
Coupling Mechanisms	10	(4)
Electric Field Coupling	10	(2)
Magnetic Field Coupling	12	(2)
Signal Spectra	14	(5)
Clock Signals Harmonic Frequencies	14	(3)
Hertz vs. Bits-per-Second	17	(1)
Non-Squarewave Data Signals	18	(1)
Resonance Effects	19	(2)
Magic and Luck	20	(1)
Potential Emissions Sources	21	(2)
Shielded Products	21	(1)
Unshielded Products	22	(1)
Intentional Signal Content	23	(1)
Summary	23	(2)
What is Inductance?	25	(18)
Introduction	25	(1)
Electromagnetic Induction	25	(2)
Mutual Inductance	27	(2)
Self-Inductance	29	(7)
Self-Inductance per Unit Length	33	(3)
Partial Inductance	36	(4)
Summary	40	(3)
The Ground Myth	43	(26)
Where Did The Term ``Ground'' Originate?	43	(3)
What Do We Mean When We Say ``Ground''?	46	(9)
Signal Reference	46	(3)
Power Reference	49	(1)
Chassis Reference	50	(1)
Unshielded Cables	51	(3)
Shielded Cables	54	(1)
Earth Safety Reference	55	(1)
`Ground' is Not a Current Sink	55	(1)
Referencing Strategies	55	(3)
Single-Point Ground-Reference Strategy	56	(1)
Multi-Point Ground-Reference Strategy	56	(2)
Grounding Heatsinks to PC boards	58	(6)
Heatsink ``Grounding'' Example	61	(3)
PCB Reference Connection to Chassis Reference	64	(2)
I/O Area Connection	64	(2)
Summary	66	(3)
Return Current Design	69	(16)
Introduction	69	(2)
Split Reference Planes	71	(5)
Stitching Capacitors	72	(4)
Trace Changing Reference Planes	76	(4)
Motherboards and Daughter Cards	80	(3)
Connector Pin Assignments	82	(1)
Summary	83	(2)
Controlling EMI Sources -- Intentional Signals	85	(20)
Introduction	85	(1)
Critical Signals	86	(1)
Intentional Signals	86	(7)
Intentional Signals -- Loop-Mode	93	(2)
Controlling Emissions from Intentional Signals -- Loop-Mode	95	(1)
Intentional Signals -- Common-mode	96	(3)
Intentional Signals -- Common-mode with Interrupted Return Path	99	(3)
Critical Signal Traces Crossing Splits	99	(1)
Critical Signals Through Vias	100	(2)
Summary	102	(3)
Controlling EMI Sources -- Unintentional Signals	105	(16)
Introduction	105	(1)
Unintentional Signals	106	(1)
Unintentional Signals -- Common-mode	106	(2)
Controlling Emissions from Unintentional Signals -- Common-mode	108	(5)
Unintentional Signals -- `Crosstalk' Coupling onto I/O Lines	113	(2)
Controlling Emissions from Unintentional Signals -- `Crosstalk' Coupling to I/O Lines	115	(3)
Summary	118	(3)
Decoupling Power/Ground Planes	121	(30)
Introduction	121	(1)
Background	122	(2)
Calculating the Source of Decoupling Noise	124	(6)
Decoupling Noise from ASIC/ICs power pins	124	(6)
Decoupling Capacitor Effectiveness	130	(18)
Test Board Description	131	(3)
Empty Test Board Configuration	134	(2)
Quantity of Distributed (Global) Decoupling Capacitors (.0luf Only)	136	(1)
Quantity of Distributed Decoupling Capacitors (0.0luf and 330 pF)	137	(3)
Selecting the Value of the Decoupling Capacitors	140	(1)
Perfect Decoupling Capacitors	140	(1)
Source Vs Distributed Decoupling	141	(3)
Buried Capacitance Decoupling	144	(2)
Lossy Capacitors	146	(2)
Summary	148	(3)
EMC Filter Design	151	(20)
Introduction	151	(1)
Filter Design Concepts	151	(4)
Filter Configurations	155	(8)
Two-Component Filter Configurations	155	(2)
Reference Connection for Two-Component Filters	157	(4)
Three Component Filter Configurations	161	(2)
Single Component Filter Configurations	163	(1)
Non-Ideal Components and the Impact on Filters	163	(5)
Non-Ideal Capacitors	164	(2)
Non-Ideal Ferrite Beads	166	(2)
Non-Ideal Zero Ohm Resistors	168	(1)
Common-Mode Filters	168	(1)
Summary	169	(2)
Using Signal Integrity Tools for EMC Analysis	171	(16)
Introduction	171	(1)
Intentional Current Spectrum	172	(5)
Trace Current for Decoupling Analysis	177	(2)
Differential Signals Analysis	179	(6)
Internal Differential Signal Lines	181	(1)
External I/O Differential Signal Lines	182	(3)
Crosstalk Analysis	185	(1)
Summary	185	(2)
Printed Circuit Board Layout	187	(12)
Introduction	187	(1)
PC Board Stack-up	187	(8)
Many Layer Boards	188	(3)
Six-Layer Boards	191	(1)
Four-Layer Boards	192	(1)
One and Two-Layer Boards	193	(2)
Component Placement	195	(1)
Isolation	195	(1)
Summary	196	(3)
Shielding in Enclosures with Apertures	199	(22)
Introduction	199	(3)
Resonance Mode within Shielded Enclosures	202	(6)
Shielded Enclosures	208	(5)
Apertures and Openings	208	(2)
Gaskets	210	(3)
Predicting the Shielding Effectiveness of Enclosures with Apertures	213	(2)
Shielding the PC Board Edge	215	(1)
Cable Shields	216	(2)
Summary	218	(3)
What To Do If a Product Fails in the EMC Lab	221	(10)
Introduction	221	(1)
Where Does the Signal Come From?	222	(1)
How Does the Signal Get Out of the Shielded Enclosure?	223	(4)
Leaks through slots holes and apertures	223	(2)
Conducted through the shield on cables and wires	225	(1)
Leaks from imperfect mating of shielded cable shields to the enclosure	226	(1)
Coupling Mechanism	227	(2)
Case 1 Clock signal leaking from seam	228	(1)
Case 2 Clock signal leaking from an unshielded cable	228	(1)
Summary	229	(2)
Appendix A Introduction to EMI/EMC Computational Modeling	231	(10)
A.1 Introduction	231	(1)
A.2 Why Is EMI/EMC Modeling Important?	232	(1)
A.3 EMI/EMC Modeling: State of the Art	233	(1)
A.4 Tool Box Approach	234	(1)
A.5 Brief Description of EMI Modeling Techniques	235	(4)
A.5.1 Finite Difference Time-Domain	235	(2)
A.5.2 Method of Moments	237	(1)
A.5.3 Finite Element Method	238	(1)
A.6. Other Uses for Electromagnetic Modeling	239	(1)
A.7. Summary	239	(2)
Index	241