EMC Crosstalk between PCB Traces

Transcription

1 EMC Crosstalk between PCB Traces West Michigan EMC Chapter Meeting - May 30, 2013 Bogdan Adamczyk, Ph.D., in.c.e. Grand alley State University

2 Outline 1. Electromagnetic fields and crosstalk 2. Inductive and capacitive coupling 3. Circuit model 4. Circuit analysis 5. PCB measurements 6. Conclusions and design implications 2

3 PCB Crosstalk Crosstalk - unintended electromagnetic coupling between PCB traces. oltage (or current) from one circuit, called the generator or aggressor circuit, induces voltage (or current) at the terminals of another circuit, called the receptor or victim circuit. Important EMC concern: design the product that does not interfere with itself. 3

4 PCB Geometry and Fields Coupling PCB Geometry 4

5 Fields Coupling vs. Inductive and Capacitive Coupling 5

6 PCB Geometry and Circuit Model PCB Geometry Generator and eceptor Circuit Model EMC problem to solve: Given: S (t), S,,, Determine: (t), (t) 6

7 Crosstalk Model in eceptor Circuit Generator and eceptor Circuit Model Crosstalk Model in eceptor Circuit 7

8 Principle of Superposition eceptor circuit with both sources present 8

9 Partial Induced oltages t m di dt G t m di dt G t C m d dt G t C m d dt G 9

10 Total Induced oltages eceptor circuit t m di dt G C m d dt G Total induced voltage at near end. t m di dt G C m d dt G Total induced voltage at far end. 10

11 Total Induced oltages Generator Circuit elationship between the generator signals and the source signals, valid for electrically short traces: G t S S t I G t S 1 S t t 1 m S InductiveCoupling Cm S CapacitiveCoupling d S dt t Total induced voltage at near end. t 1 m C S InductiveCoupling ds dt m S EMC Chapter Meeting May 30, 2013 CapacitiveCoupling t Total induced voltage at far end. 11

12 PCB Board 12

13 PCB Board ayout 13

14 Experimental Set-Up 14

15 Case 1 15

16 Case 2 16

17 Case 3 17

18 Design Implications Induced crosstalk voltage is proportional to d/dt and board geometry. To reduce crosstalk: - Increase the rise and fall times - Move ground plane closer to the signal plane - Move signal traces in the signal plane farther apart 18

19 Crosstalk in Frequency Domain 1 jm S S inductivecoupling jcm S S capacitivecoupling 1 jm S jcm S S S inductivecoupling capacitivecoupling 19

20 Transfer Function esponse 1 jm S S inductivecoupling jcm S S capacitivecoupling jm S jcm S S S 1 inductivecoupling capacitivecoupling S S j j IND CAP M M jm IND CAP M M jm Crosstalk increases 20 db/decade. 20

21 Crosstalk at 1 MHz Case 1 21

22 Crosstalk at 10 MHz Case 1 22

23 eferences and Acknowledgements B. Adamczyk, J. Teune EMC Hardware Demonstration PCB Crosstalk 2008 IEEE International EMC Symposium, Detroit, MI Bill Spence and Pete ander Wel, Gentex Corp. Board Design C.. Paul, Introduction to Electromagnetic Compatibility, 2 nd Ed,, 2006 H. W. Ott, Electromagnetic Compatibility Engineering 2009 B. Adamczyk, ecture Notes, GSU,

24 Next EMC Chapter Meeting Wed, June 19, 2013 Dennis M. ewis Associate Technical Fellow, Boeing The Impact of Cables and Connectors on adio Frequency and Microwave Measurement Uncertainties More details at: 24