The PCB Design Magazine – April 2017
Beyond Design: Return Path Discontinuities
Simultaneous switching noise is a major problem in high-speed
systems. But, the underlying issue is really the management of
transmission line return currents that flow on the nearby reference
planes, causing the planes to bounce. High-speed design is not as
simple as sending a signal over an interconnect. But rather, one
should also consider the interaction of the PDN and how and where
the return current flows.
The PCB Design Magazine – March 2017
Beyond Design: Microstrip Coplanar Waveguides
Coplanar Waveguides (CPW) have
been used for many years in RF and microwave design as they reduce
radiation loss, at extremely high frequencies. And now, as edge
rates continue to rise, they are coming back into vogue. Today’s
high-speed, fast rise time serial interfaces are prone to excess
loss, in the transmission lines, which is a major cause of signal
The PCB Design Magazine – February 2017
Beyond Design: New Functionality Improves
Productivity features not only save time-to-market but also curb
frustration. One of the main details lacking in today’s PCB design
software is the flow of impedance control from design capture
through to board fabrication. If the impedance, of all the required
technologies, is determined up-front at the time of capture, the
engineer’s intent should be preserved and flow through to downstream
The PCB Design Magazine – January 2017
PDN - Decoupling Capacitor Placement
The impact of lower core voltages and faster edge rates has pushed
the frequency content of typical digital signals into the gigahertz
range. Consequently, the performance of decoupling capacitors, that
are required to complement the Power Distribution Network (PDN) and
curb signal induced fluctuations, must also be extended up into this
range. This month, I look at effective decap placement.
The PCB Design Magazine – December 2016
Marketing in the Maturing EDA Industry
In this month's column, Barry Olney explains how Electronics Design
Automation (EDA) sales and marketing techniques have evolved as EDA
has matured, and traces the drop in tool cost over time, along with
the increase in tool capability.
The latest EDA offerings provide highly productive tools for the
ever increasing number of global users, at an affordable price
point. Really, it has never been better!
The PCB Design Magazine – November 2016
Beyond Design: Uncommon Sense - Differential
It is remarkable that with all of today’s high performance systems,
in which very complicated electromagnetic effects play a dominant
role, many of us still hold misconceptions about the fundamental
nature of how signals interact with interconnects. In this month’s
column, I will look at the contemporary ways of addressing an old
issue (Déjà View – as I call it) and go
beyond the design of PCBs.
The PCB Design Magazine – October 2016
Beyond Design: Rock Steady Design
do we ensure that our high-speed digital design performs to
expectations, is stable given all possible diverse environments and
is reliable over the products projected life cycle? One word:
For very little extra effort, your design can have improved
performance and reliability giving you greater confidence in your
products performance for the projected lifetime.
The PCB Design Magazine – September 2016
Beyond Design: How to Handle the Dreaded
In Part 1 of this series, I deliberated on how
dangling via stubs distort signals passing through an
interconnect and also decrease the usable bandwidth of the signal.
The conventional solution, to this
problem, is to back-drill (or control depth drill) the vias to bore
out the via stub barrels, so that the via stubs are reduced in
length if not completely removed. This month I will look into all
the possible solutions to alleviate this issue.
The PCB Design Magazine – August 2016
Beyond Design: How to Handle the Dreaded
Dangling via stubs can distort signals passing through an
interconnect and also decrease the usable bandwidth of the signal. A
via stub acts as a transmission line antenna, and has a resonant
frequency determined by the quarter wavelength of the structure. At
this frequency, the transmitted signal is greatly attenuated–by up
to 3dB. This month, I look at the issues created by via stubs and
how to resolve them.
The PCB Design Magazine – July 2016
Beyond Design: The Rise of the Independent
With the changing demographics, the old timers –
the master PCB designers – are about to retire and hand-over the
exacting job of PCB design to the Gen-X and Ys. These generations
will tackle the most demanding designs without possessing the
experience that we veterans benefit from. Apart from a demanding
regime of training, what can these guys do to become a successful
The PCB Design Magazine – June 2016
Beyond Design: Mastering "Black Magic"
Dr. Howard Johnson, the world’s foremost authority on Signal
Integrity, has recently released his High-Speed Digital Design (HSDD)
Collection. This includes, professionally recorded seminars that he
presented, for over 20 years, at Oxford University and worldwide and
is arguably the most practical and enlightening course on high-speed
– black magic – ever delivered. This month I review the Collection.
The PCB Design Magazine – May 2016
Beyond Design: Artificial Intelligence in EDA
The keynote speaker at
the Apex Design Forum, in Las Vegas this year, was Dean Parker, a
manager at Google X. Parker specializes in Artificial Intelligence
(AI). He said that EDA tool vendors need to trash all their old
1990s code and start over–this time with artificial intelligence.
But, how could AI influence the PCB design process. This month, I
will take a look at the endless possibilities.
The PCB Design Magazine – April 2016
Beyond Design: DDR3/4 Fly-by vs T-topology
DDR3/4 Fly-by topology supports higher frequency
operation, reduces simultaneous switching noise, reduces the
quantity and length of stubs and consequently improves signal
integrity. And, for a PCB designer – eases routing of memory devices
dramatically. However, strict attention should be paid to the signal
propagation, on each layer, ensuring the total flight time of the
critical signals match, regardless of length.
The PCB Design Magazine – March 2016
Beyond Design: The Need for Speed - Strategies
for Design Efficiency
Years of experience with the one EDA tool
obviously develops efficiency whether the tool be high-end feature
packed or basic entry-level. And, one becomes accustomed to the
intricacies of all the good and bad ‘features’ of their PCB design
tool. However, there comes a time where one should consider a change
for the better. This month, I will look at productivity issues that
impede the PCB design process.
The PCB Design Magazine – February 2016
Beyond Design: Faster Than a Speeding Bullet
The speed of a computer does not depend
intrinsically on the speed of electrons, but rather on the speed of
energy transfer between electronic components. Electron flow, in a
multilayer PCB, is extremely slow – about 10mm per second – so how
does the signal travel so fast, how fast does it actually transfer
information and what are the limitations?
The PCB Design Magazine – January 2016
Beyond Design: Plane Crazy Part 2
In the recent, four part, Stackup Planning series of columns I
described the best configurations for various stackup requirements
but I did not have the opportunity to delve into the use of planar
capacitance to reduce the AC impedance at frequencies above 1GHz. In
this column, I will flesh out this topic, and consider the effects
of plane resonance on the Power Distribution Network (PDN).
The PCB Design Magazine – December 2015
Beyond Design: Plane Crazy Part 1
A PDN must provide a low inductance, low
impedance path between all ICs. In order to reduce the inductance,
we must also minimize the loop area enclosed by the current flow.
Obviously, the most practical way to achieve this is to use power
and ground planes. In this two part column, I will look at the
alternatives to planes, why planes are used for high-speed design
and the best combination for your application.
The PCB Design Magazine – November 2015
Beyond Design: Why Autorouters Don't Work -
Ask any group of PCB Designers what they think of autorouters and
the majority will say that they don't use them because they don't
work. I have been battling this mindset for over twenty years now
and it still persists today, even with the dramatic advances in
routing technology. But, even the most
primitive autorouter may have some useful features. It’s all about
changing that mindset of the designer and having a crack at it.
The PCB Design Magazine – October 2015
Beyond Design: Stackup Planning Part 4
In the final part of the Stackup Planning series I will look at 10
plus layer counts. The methodology I have set out, in previous
columns, can be used to construct higher layer count boards. In
general, these boards contain more planes and therefore the issues
associated with split power planes can usually be avoided. Also, ten
plus layers require very thin dielectrics, in order to reduce the
total board thickness.
The PCB Design Magazine – September 2015
Top Gear - PADS Professional Road Test
We hear all the hype about new EDA tools but how
do they actually perform on your design? This month Barry Olney road
tests Mentor Graphics’ new PADS Professional and puts it through a
rigorous performance evaluation – let’s see how the Xpedition
technology actually performs integrated into the PADS tools.
The PCB Design Magazine – August 2015
Beyond Design: Stackup Planning Part 3
This month I will look at higher layer count
as the four and six layer configurations are not the best choice.
Each signal layer should be adjacent to, and closely coupled to, an
uninterrupted reference plane, which creates a clear return path and
eliminates broadside crosstalk. As the layer count increases, these
rules become easier to implement but decisions regarding return
current paths become more challenging.
The PCB Design Magazine – July 2015
Beyond Design: Stackup Planning Part 2
In Part 1 of the Stackup Planner series, I looked
at how the stackup is built, the materials used in construction and
the lamination process. And, I set out some basic rules to follow
for high-speed design. It is important keep return paths, crosstalk
and EMI in mind during the design process. Part 2 follows on from
this with definitions of basic stackups starting with four and six
The PCB Design Magazine – June 2015
Beyond Design: Stackup Planning Part 1
The PCB substrate that physically supports the
components, links them together, via high-speed interconnects and
also distributes high current power to the ICs, is the most critical
component of the electronics assembly. The PCB is so fundamental,
that we often forget that it is a component and like all components,
must be selected based on specifications in order to achieve the
best possible performance.......
The PCB Design Magazine – May 2015
Beyond Design: Controlled Impedance Design
For perfect transfer of
energy, the impedance of the driver must match the transmission
line. A good transmission line is one that has constant impedance
along the entire length of the line, so that there are no mismatches
resulting in reflections. But unfortunately, drivers do not have the
exact impedance to match the line so terminations are used to
balance the impedance, match the line and minimize
The PCB Design Magazine – April 2015
Beyond Design: Learning the Curve
Currently, power integrity is just entering
the mainstream market phase of the technology adoption life cycle.
The early market is dominated by innovators and visionaries who will
pay top dollar for new technology, allowing complex and expensive
competitive tools to thrive. However, the mainstream market waits
for the technology to be proven before jumping in. More about the
PDN learning curve ........
The PCB Design Magazine – March 2015
Beyond Design: Split Planes in Multilayer PCBs
Creating split planes in multilayer PCBs at first seems like a good
idea. These days’ processors require more than six or seven
different high current power sources. And, keeping sensitive analog
circuitry isolated from those nasty, fast, digital switching signals
seems like a priority in designing a noise free environment for your
product – or is it?
The Electronic Specifier Design Magazine –
Better software features
highly in driving up productivity and reliability. As designs become
more complex and time-to-market schedules become more demanding,
engineers must take advantage of pre-layout simulation, and
simultaneous process design in order to beat the competition.
Electronic Specifier Design –
The PCB Design Magazine – February 2015
Beyond Design: Effects of Surface Roughness on
Below 1GHz, the effect of
copper surface roughness on dielectric loss in negligible. However,
as frequency increases, the skin effect drives the current into the
surface of the copper dramatically increasing loss. The effective
resistance of the copper increases relative to the additional
distance over which the current must transverse the surface
The PCB Design Magazine – January 2015
Beyond Design: Electromagnetic Susceptibility
As PCB Designers, we are concerned with electromagnetic emissions,
as every product we design must pass the FCC/CISPR compliancy, but
what about susceptibility to external sources? Noise sources range
from medium to high frequency, RF and microwave radiation and can be
generated by nearly any electrical appliance or device.
The PCB Design Magazine – December 2014
Beyond Design: Signal Integrity - Part 3 of 3
Where most designers go wrong and how to avoid the common pit-falls.
Digital designs become less forgiving as edge rates and frequencies
increase. What used to work, in the past, may not now and a
different approach to layout may be necessary. Also, there may be
many issues that aren’t at first apparent but affect the reliable
performance of the product.
The PCB Design Magazine – November 2014
Beyond Design: Signal Integrity - Part 2 of 3
In last month’s column, I
looked at how advanced IC fabrication techniques have created havoc
with signal quality and radiated emissions. Part 2, of Signal
Integrity, will cover the effects of crosstalk, timing and skew on
The PCB Design Magazine – October 2014
Beyond Design: Signal Integrity - Part 1 of 3
As system performance
increases, the PCB designer’s challenges become more complex. The
impact of lower core voltages, high frequencies
and faster edge rates has forced us into the high-speed digital
domain. But in reality, these issues can be overcome by experience
and good design techniques.
Dataweek Magazine – October 2014
Concurrent Design Cuts Development Costs and
As The traditional PCB
design process is to execute each stage of the design in sequence.
But, as designs become more complex and time-to-market schedules
become more demanding, one must take advantage of pre-layout
simulation, and simultaneous process design in order to beat the
competition. Dataweek Magazine - South African edition.
The PCB Design Magazine – August 2014
Material Selection for Digital Design
Materials used for the
fabrication of the multilayer PCB absorb high frequencies and reduce
edge rates and that loss, in the transmission lines, is a major
cause of signal integrity issues. But we are not all designing
cutting-edge boards, and sometimes we tend to over-specify
requirements that can lead to inflated production costs.
The PCB Design Magazine – July 2014
Beyond Design: Concurrent Design
With the traditional PCB
design process, the designer executes each stage of the design in
sequence. But, as designs become more complex and time-to-market
schedules become more demanding, we must take advantage of
pre-layout simulation, and simultaneous process design in order to
beat the competition.
The PCB Design Magazine – June 2014
Surface Finishes for High-Speed Design
immersion gold (ENIG) finish has traditionally been the best fine
pitch (flat) surface and lead-free option for SMT boards over recent
years. But unfortunately, nickel is a poor conductor with only 1/3
the conductivity of copper. Also, nickel has a ferromagnetic
property that can adversely affect electromagnetic fields in the
The PCB Design Magazine – May 2014
From barbed wire to
high-speed interconnect. Long before Facebook and Twitter, there was
a more primitive type of social network. It allowed distant
communities to meet remotely to share music, spread news and to just
gossip. The long-forgotten social revolution, and extremely basic
technology, was built on barbed wire fences.
The PCB Design Magazine – April 2014
Mythbusting - There are no on-way trips
One of the greatest myths
in PCB design is that we only have to route signal traces from
pin-to-pin to make a complete connection. And, that ensuring these
traces have matched delay is the only timing issue we need to
consider. However, current is not a one way trip—it must complete
the circuit back to the source in order to provide the round-trip
The PCB Design Magazine – March 2014
Matched Length does not equal Matched Delay
In previous columns, I have discussed matched
length routing and how matched length does not necessarily mean
matched delay. But, all design rules, specified by chip
manufacturers regarding high-speed routing, specify matched
length—not matched delay. In this month’s column we’ll take a look
at the actual differences between the two.
The PCB Design Magazine – February 2014
Effective Routing of Multiple Loads
Different terminating strategies have
advantages and disadvantages depending on the application, but in
general, series termination is excellent for point-to-point routes,
one load per net. In summary, series termination reduces ringing and
ground bounce. But, what if there are a number of loads—how should
these transmission lines be routed?
The PCB Design Magazine – January 2014
PDN Planning and Capacitor Selection Part 2
In last month’s column we looked closely at how to choose the right
capacitor to lower the AC impedance of the PDN at a particular
frequency. We also examined capacitor properties and types of
capacitors that are readily available and touched on the target
frequency approach for analyzing a PDN. This month we will continue
on from there looking at the one capacitor value per decade and
optimized value approaches.
The PCB Design Magazine – December 2013
PDN Planning and Capacitor Selection Part 1
In a previous column, I described the basics
of planning for a low AC impedance, between the planes, in order to
reduce supply noise and provide reliable performance. This column,
spread over two parts, will focus on capacitor selection and
three alternative approaches to analyzing the Power Distribution
The PCB Design Magazine – November 2013
Beyond Design: Entanglement – The Holy Grail
of High-speed Design
While high-speed SERDES serial communications
seems to currently be at the cutting edge of technology, maybe it
will shortly become an antiquated low-speed solution—even
speed-of-light fiber optics may become obsolete. This month, we’ll
look at how quantum physics is transforming our world and how it
could affect PCB design.
The PCB Design Magazine – October 2013
Beyond Design: Impedance Matching –
The impedance of the trace is extremely
important, as any mismatch along the transmission path will result
in a reduction in signal quality and possibly the radiation of
noise. By understanding the causes of these reflections and
eliminating the source of the mismatch, a design can be engineered
with reliable performance.
The PCB Design Magazine – September 2013
Beyond Design: Material Selection for SERDES
Many challenges face the engineer and PCB
designer working with new technologies. Materials used for the
fabrication of the multilayer PCB absorb high frequencies and reduce
edge rates thus putting the materials selection process under
tighter scrutiny. This column will look at the factors that must be
taken into account, in the selection process, and provides some
options for PCB designers.
The PCB Design Magazine – August 2013
Beyond Design: Practical Signal Integrity
"There are two types of designers: Those that
have signal integrity problems and those that will." — Sun
If you are a digital designer, you will
eventually have SI problems whether you like it or not. But all is
not lost. If you learn to work with these issues, then you will soon
become proficient with high-speed design.
The PCB Design Magazine – July 2013
Beyond Design: Design for Profit
Design for Profit is gaining more recognition
as it becomes clear that the cost reduction of printed circuit
assemblies cannot be controlled by manufacturing engineers alone.
The PCB designer now plays a critical role in cost reduction.
PCB Design Magazine – June 2013
Beyond Design: Skewed Again
Differential skew refers to the time
difference between the two single-ended signals in a differential
pair. Any mismatch in delay (skew) will result in changing part of
the differential signal power into common-mode power. When skew
needs to be adjusted, it is best done at either end of the
differential pair. In this way, the coupling and signal quality of
the remainder of the pair is maintained.
The PCB Design Magazine – May 2013
Beyond Design: Losing a Bit of Memory
No matter what type of memory you are
designing with, the clock should always have the longest delay. This
ensures that the other signals have time to settle before the clock
arrives at the device and samples the bus.
The PCB Design Magazine – April 2013
Beyond Design: Electromagnetic Fields, Part 2
In my last column, Electromagnetic Fields:
Part 1, we looked at how magnetic fields revolve around the earth
and how these fields are also present in a multilayer board. In Part
2, we will look at how electromagnetic fields influence transmission
lines and how they can be applied in a BEM field solver.
The PCB Design Magazine – March 2013
Beyond Design: Electromagnetic Fields, Part 1
Danish physicist Hans Christian Oersted
discovered that electric currents create magnetic fields. He later
found that a current-carrying wire created a circular magnetic field
around that wire, and that this circular field was strongest closer
to the wire. Traces in a multilayer PCB act in much the same way. A
current loop produces a field similar to that of the Earth.
The PCB Design Magazine – February 2013
Beyond Design: Post Mortem Simulation
Often we find that PCB simulation is engaged
too late in the design cycle. This results in the simulation process
becoming more a post-mortem to uncover what has gone wrong with the
design and how it can be resurrected to work as intended.
The PCB Design Magazine – January 2013
Beyond Design: Routing Techniques for Complex
To err is human; to completely mess it up, use
software. Autorouter software is essentially artificial intelligence
(AI) software – although fairly basic – that makes certain decisions
that mimic what designers do in the process of routing a board. Its
capacity to do this, of course, varies by software developer, and is
dependent upon algorithm complexity and how easy or difficult it is
to control the router.
The Electronics News – January 2013
Multilayer PCB Simulation – Barry Olney
Faster edge rates cause reflections and signal
quality problems. And, although the package and your clock speed
have not changed a problem may exist for legacy designs. The
enhancements in driver edge rates have a significant impact on
signal quality, timing, crosstalk, and EMC. So whether you like it
or not – you are now a high-speed designer.
The PCB Design Magazine – December 2012
Beyond Design: Interactive Placement and
PCB layout is a means to combine your artistic
side and your creative skills with the power of automation. I always
say that if a PCB design looks good, it will probably work well.
However, neatness in routing often leads to unwanted crosstalk as
trace segments are routed in parallel for long distances.
The PCB Design Magazine – November 2012
Beyond Design: The Plain Truth About Plane
Moats, islands, cut-outs in the ground plane,
isolated power planes, floating ground regions are often used by PCB
designers to reduce crosstalk, EMI. But a high-speed signal crossing
a split in the plane causes problems along at least three
dimensions, including signal quality, crosstalk, and EMI. The
problem is the impedance discontinuity in the signal path crossing
The PCB Magazine – September 2012
Beyond Design: Critical Placement
Today's high-speed digital products use high
frequencies and fast rise times that demand careful attention to PCB
layout to ensure that the system works not only in the prototype
phase, but also in mass production, and under all possible operating
The PCB Magazine – August 2012
Beyond Design: Mixed Digital-Analog
Field programmable gate arrays (FPGAs) are
becoming more complex, integrating functions such as processors,
multi-gigabit SERDES transceivers and support for multiple I/O
standards. However, designing power management and signal paths
(including analog-to-digital converters, operational amplifiers and
interface) around these FPGAs is no easy task.
The PCB Magazine – July 2012
Beyond Design: Pre-Layout Simulation
Today’s high-speed processors, SERDES
interfaces and decreased time-to-market requirements are pushing
design teams toward more nimble development processes. But there is
no point in completing a design on time if it does not work! My
motto is: “Simulate twice – build once.”
The PCB Magazine – June 2012
Beyond Design: Design Rules & DFM for
Requirements for PCB design can vary
considerably from one design to the next. I specialize in high-speed
design (HSD) but I am often asked to do a board that incorporates a
switch-mode power supply. Or, there may be an analog section that
needs to be laid out, so the design rules I use vary depending on
the application. Where to Start?
The PCB Magazine – May 2012
Beyond Design: Power Distribution Network
Fast rise times, low output-buffer impedance
and the simultaneous switching of busses create high transient
currents in the power and ground planes, degrading performance and
reliability of the product. Inadequate power delivery can exhibit
intermittent signal integrity issues.
The PCB Magazine – April 2012
Beyond Design: Stackup Planning and the
Back in 1987, when I first started working on
high-speed designs, the PCB stackup did not seem that important. But
that was running at a maximum frequency of 166 MHz, which at the
time seemed fast. Times have changed. Now, multi Gbps designs are
becoming the norm and the stackup configuration, characteristic and
differential impedance control are crucial to the performance and
reliability of the product.
The PCB Magazine – March 2012
Intro to Board-Level Simulation and the PCB
High-speed digital multilayer boards can be
designed to work right the first time, with little additional
effort, providing you follow a tried and proven process that results
in a reliable, manufacturable design that conforms to specifications
and is produced on time and to budget.
The PCB Magazine – February 2012
Beyond Design: Plan B - Post-Layout
Unfortunately, board-level simulation is
engaged too often towards the end of the design cycle. Ideally the
simulation should be done during the design process to ensure design
integrity. By following this year’s series of columns on Board-Level
Simulation and the Design Process, designers can be up-to-date on
the best methodology to follow.
The PCB Magazine – January 2012
Beyond Design: A New Slant on Matched-Length
Serpentine traces are commonly used for
matched length signals and supported by all popular EDA tools. It is
therefore easier to follow tradition and use this pattern. It would
be best using the serpentine pattern with at least 5x trace width
spacing in a stripline configuration to reduce crosstalk and
radiation. But, if real estate is at a premium then maybe it’s time
to give the old octal spiral a go.
The PCB Magazine – December 2011
Beyond Design: Controlling the Beast
Crosstalk creates noise that erodes the noise
margin. The degree of crosstalk is dependant of several factors
including driver strength, transmission line length, how far the
segments run closely in parallel and signal rise time. In the case
of long line lengths, a series terminator slows the signal rise time
and extinguishes reverse-coupled crosstalk at the near end,
improving crosstalk considerably.
The PCB Magazine – November 2011
Beyond Design: The Perfect Stackup – for
Throughout the past 30 years, the concept of
the perfect stackup has changed considerably. This is especially
true in more recent years, where engineers and designers have had
the opportunity to use simulation tools that act as another pair of
eyes when it comes to understanding the intricacies of the effects
of transmission lines on multilayer PCBs. This month we look at the
perfect stackup for high-speed design.
The PCB Magazine – October 2011
Beyond Design: Differential Pair Routing
Some argue that since the two halves of the
differential pair carry equal and opposite signals, a good ground
connection is not required as the return current flows in the
opposite signal. Others say that beyond the fact that differential
pairs transfer equal and opposite signals, there are no special
requirements that need to be considered when using differential
pairs. They should be treated as two single-ended signals.
The PCB Magazine – September 2011
Beyond Design: Embedded Signal Routing
We hear all the time that one should avoid
routing high-speed signals on the outer layers of a multilayer PCB.
I myself preach this. Some say that this decreases radiation by up
to 15 db. But, how much attenuation do we actually get from
embedding the high-speed signals between the planes?
The PCB Magazine – August 2011
Beyond Design: The Dumping Ground
By definition, a ground plane in a PCB is a
layer of copper that appears to most signals as an infinite ground
potential. This month, we discuss best practices for selecting
reference planes and routing pairs for high-speed designs on
PCB007 online – August 2011
Beyond Design: Controlling Emissions and
This application note discusses
electromagnetic compliancy (EMC) fundamentals and common approaches
and methodologies to suppress unintentional noise.
The PCB Magazine – June 2011
PCB Design Techniques for DDR, DDR2 & DDR3,
To improve signal integrity and support higher
frequency operations, the JEDEC committee defined a fly-by
termination scheme used with the clocks, command and address bus
signals of DDR3. Fly-by topology reduces simultaneous switching
noise (SSN) by deliberately causing skew between the
data and strobes at every chip/DRAM, requiring controllers to
compensate for this skew by adjusting the timing per byte lane.
The PCB Magazine – May 2011
PCB Design Techniques for DDR, DDR2 & DDR3,
This application note details the tried and
proven design rules and techniques for DDR PCB Design and looks at
DDR, DDR2 and DDR3 design rules and critical constraints.
PCB007 online – May 2011
Ground Pours: To Pour or Not to Pour?
Copper ground pours are created by filling
unused areas with copper and then connecting the copper fill with
stitching vias to ground. Some PCB designers do this as a matter of
habit. Also, many reference designs supplied by chip manufacturers
use this ground pour technique so you may need to follow their
recommendations if you want the design to work especially at high
Application Note - Feb 2011
Multilayer PCB Stackup Planning
Planning the multilayer PCB stackup
configuration is one of the most important aspects in achieving the
best possible performance of a product. A poorly designed substrate,
with inappropriately selected materials, can degrade the electrical
performance of signal transmission increasing emissions and
crosstalk and can also make the product more susceptible to external
Application Note - Dec 2010
Generic Multilayer PCB Specification
This specification has been developed for the
specifaction of fabrication of rigid SMT and
Mixed Technology Multilayer Printed Circuit Boards (PCB's) of less
than 12 inches [300 mm] square.
Printed Circuit Design Magazine – January 1996
Design for EMC – Barry Olney
In order to accurately predict potential
problem areas, minimize electromagnetic interference and
susceptibility and verify their design, today's PCB designers not
only need to plan for EMC but also must use software to analyse the
physical layout. As clock speeds approach 50 MHz, signal integrity
issues should be considered.