Decoupling and Grounding of High Speed Digital Circuits

 Ineffective decoupling and grounding of high speed digital logic systems is a major cause of radiated and conducted emissions, as well as increased susceptibility to both internal and external noise sources.  Most designers still use the 40 year old technique of placing a 0.1 uF capacitor next to an IC to provide decoupling without any analytic understanding, or empirical verification, of the effectiveness of this approach.

 This one-day seminar covers the mechanisms by which digital logic circuits generate noise, and the effectiveness and limitations of the various approaches to decoupling and grounding.  Methods of overcoming these limitations by the use of multiple capacitors, ferrites, distributed capacitance, and isolated power planes are investigated.  The interactions between ground plane, power plane, and the decoupling capacitance are discussed.  The significance of ground voltage drop, and methods of minimizing it are also presented.  Participants will gain a better understanding of the limitations of traditional decoupling methods and a knowledge of new technology and modern approaches to overcome these limitations.



Characteristics of a Power Distribution System
Power Distribution System Requirements
Inductance and Resonance
Equivalent Circuit of Decoupling Network
Power Entry Filtering
Alternative Decoupling Methods
Effect of Paralleling Capacitors
Equal Value Verses Different Value Capacitors
Multiple Decoupling Capacitors
Decoupling Network Impedance
How Does Decoupling Relate to Radiation?
Effective Frequency Range
Multiple Decoupling Capacitor - Example
Embedded PCB Capacitance
Power Plane Isolation
Summary of Decoupling Options

Ground Plane Impedance

IC Package Inductance
Ground Plane Current Flow
Ground Plane Inductance
Effect of Vias on Ground Inductance
The Use of Multiple Vias
AC Resistance of Ground Planes
Ground Plane Impedance vs Trace Height & Frequency
Summary & Conclusions

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Henry Ott Consultants
48 Baker Road Livingston, NJ 07039
Phone: 973-992-1793,   FAX: 973-533-1442

May 7, 2002