Power Integrity Modeling and Design for Semiconductors and Systems
Authors: M. Swaminathan, A. Ege Engin
Publisher: Prentice Hall, November 2007
In the real world of high speed digital package and board design,
there is no doubt that EMC issues have always had an origin in
a not so judicious design of the power distribution network.
Professionals such as EMC and signal integrity engineers, package
designers, and system architects need to thoroughly understand
signal and power integrity issues in order to successfully design
packages and boards for high speed systems from a functional and
EMC system-level point of view.
Using realistic case studies and downloadable software examples,
this book demonstrates today’s best techniques for designing
and modeling interconnects to efficiently distribute power in
digital systems and minimize electromagnetic noise. The book covers
two aspects of power distribution: design and modeling, with an
emphasis on modeling.
The book is composed into five chapters and two appendices totalling
some 470 pages. It comes with a link to the following URL http://www.powerintegrity.net/
where one can freely download the software tools used in the book.
All chapters contain several examples to illustrate the concepts,
some of which can be reproduced using the above-mentioned software.
These examples can also be used to evaluate the accuracy and speed
of several commercial tools that are available today.
Chapter 1, “Basic Concepts,” is for engineers and
students who are entering the field of power integrity. The basic
concepts are covered in this chapter, which includes a discussion
on the fundamentals of power supply noise, its role in the speed
of a computer system, the parasitics that produce it, and its
effect on jitter and voltage margin for high-speed signal propagation.
The entire book is based on the parameter called target impedance,
which can be used to evaluate the properties of a power distribution
network. The target impedance is therefore explained in detail
in Chapter 1, with examples that can be reproduced using a circuit
simulator such as SPICE. The concept of target impedance is used
to promote a better understanding of the placement of decoupling
capacitors. The components of a power distribution network consist
of several voltage regulator modules, decoupling capacitors, package
and board interconnections, planes, and on-chip interconnections,
each of which are explained in this chapter. Planes represent
a very critical part of modern power distribution networks. Their
frequency behaviour can either reduce power supply noise or increase
it by a large amount. Hence, a fundamental understanding of plane
behaviour and its effect on advanced power distribution networks
is necessary. The fundamental behaviour of planes is covered in
Chapter 1, with a focus on standing waves, their frequency of
occurrence, capacitive and inductive behaviour, and use of decoupling
capacitors to minimize their effect. The interaction between components
of a power distribution is as important as the components themselves.
For example, a surface-mount device (SMD) capacitor can interact
with the via inductance, causing the self-resonance frequency
to shift to a lower frequency; the chip can interact with the
package, causing an anti-resonance; or the power supply noise
can couple into a signal line, causing excessive jitter. The basics
associated with such phenomena are covered in Chapter 1. In the
same chapter, a methodology is presented that focuses on frequency
domain analysis initially, followed by time domain analysis.
Planes are the focus of Chapter 2, “Modeling of Planes,”
which covers the various methods available for plane modeling.
Commercial tools use some of these methods today. This chapter,
which requires some background in numerical modeling, provides
a survey of modeling methods along with examples that are useful
to a designer and can be used to evaluate commercial tools for
accuracy and speed. The in-depth numerical formulations can be
reproduced in MATLAB and hence are useful to both students and
application engineers who are interested in power integrity modeling.
The Maxwell’s equations have been converted into circuit
representations, and this makes the numerical formulations in
this chapter easy to understand. The modeling methods are separated
into lumped element modeling and distributed modeling methods,
each covered in detail. The chapter starts with modelling a plane
pair and then explains modeling of multilayered planes. The coupling
effects in multilayered planes, which include field penetration
concepts, aperture coupling, and wraparound currents, are discussed,
and the plane modeling methods are compared from a qualitative
standpoint. This comparison, along with the examples in the chapter,
allows a practicing engineer to benchmark commercial tools.
Signals from the output of a driver are propagated on signal line
interconnections. However, the driver requires voltage and current
to function, and these are supplied by the power distribution
network. The signal and power interconnections therefore have
to be coupled, with noise on one producing noise on the other.
Hence, managing both signal and power integrity requires an understanding
of the coupling mechanism between the signal lines and planes.
Chapter 3, “Simultaneous Switching Noise,” covers
these topics and it requires little understanding of numerical
methods. The entire chapter is based on circuit-level implementations
using a concept called modal decomposition, which allows the separation
of signal lines from the power distribution network so that each
can be analyzed separately and later combined for analysis. In
my opinion, the important concept offered in this chapter is the
role of return currents, their behaviour and effect for generating
noise on the power supply. Through a fundamental understanding
of the return path discontinuities discussed in this chapter,
it is possible to minimize noise.
Chapter 4, “Time-Domain Simulation Methods,” describes
methods for converting a frequency response into a SPICE subcircuit.
Also called macromodeling, this is a new area of time-domain simulation
that is ripe for research. The early part of the chapter is easy
to follow; it requires some mathematics background and is therefore
targeted at designers who use commercial tools. Several examples
illustrate simple concepts that can be reproduced using MATLAB.
The latter part of the chapter can be intense and is mainly intended
for people working in the numerical modeling area. The purpose
of this chapter is to provide an introduction to the issues of
stability, passivity and causality that can affect the eye diagrams
of high-speed channels due to non-physical effects.
In Chapter 5, “Applications,” all of the issues discussed
in Chapters 1 to 4 are linked to real-world examples. Several
examples from companies such as Sun Microsystems, IBM, Oak Mitsui,
National Semiconductor, Cisco, DuPont, Panasonic, and Rambus are
provided. These applications cover both design and modeling aspects
of power integrity. Each example seems to be chosen very carefully
to ensure that a specific aspect of power integrity is addressed.
This book comes with downloadable free software for Power Integrity
called Sphinx Book (http://www.powerintegrity.net/).
This software has a nice Graphical User Interface that is easy
to use and has an output that plots S, Y or Z parameters along
with the voltage distribution. A number of examples discussed
in the book can be reproduced using the software provided.
This book’s system-level focus and practical examples make
it very useful for all students and professionals concerned with
power integrity, including electrical engineers, system designers,
signal integrity engineers, and EMC scientists. EMC