The Pulse: Application Notes—Advice for Authors

Application notes are the key to shedding light on new topics or new products and software tools in an easily digestible form. As both a consumer and an author of more application notes than I care to remember, Andy Shaughnessy posed an interesting question on whether designers should rigorously follow application notes or verify the content.

Types of Application Notes 
I tend to categorize app notes into the following areas:

  • How to set up equipment or software
  • How to apply a product or software tool to get the best results
  • Background notes, which involve explanations of the engineering or science behind a particular task or problem

The Approach 
As always, the approach I recommend depends on the nature of the note. Notes based on how to use a piece of equipment or software do require following to the letter, and personal “interpretation” can lead to disappointment when a system doesn’t set up or function as expected. Customers sometimes call to say a setup hasn’t worked as expected, so applications engineers will remote in to follow what is happening only to see the end-user miss several key steps “because they always miss those out.” For notes aimed at how best to ensure a design meets a specific need, it is always worth looking at several sources as there are often multiple correct ways to solve certain challenges.

Delivery of Content
Historically, application notes were just that: a series of written notes to help explain to a designer or fabricator how to approach a new and perhaps unfamiliar situation. And written notes are still great for this; they’re easily printed out and annotated by the reader at leisure. But increasingly, PowerPoint presentations and video clips can be used to bring application notes to life.

Each has its place, and some content suits one delivery method more than another. Some schools of thought note that different people prefer audio or video or written content for their personal learning style, so having content in several media is often preferable. However, for the content manager, this can be a nightmare to keep updated. Another alternative for designers who may prefer to mix video content with written learning is to embed appropriate video within web pages.

It is worth remembering that some readers may have a block on access to services like YouTube in a work situation, so offering the video stream from an mp4 file on the writer’s website gives an alternate source for content in these situations.

Timely
Some notes based on engineering principles stand the test of time, so it is good for the writer to make them application-agnostic—the background information depicted is timeless, with improving technology sometimes more depth needs to be added—but if the original note is well-written, then the new findings or enhanced detail can be added in a supplementary note. For example, when readers want a background to add insertion loss knowledge to impedance control knowledge, in my opinion, the best approach is to link the existing note to a new note which expands on the next level of knowledge required. Both of these types of note stand in their own right, but read together, they broaden the background knowledge and give the reader new to the subject of PCB transmission lines enough information to be able to ask further questions to expand their knowledge of the subject.

Product-related application notes can age as the product is enhanced over the years. Smart product development can minimize the UI changes, so the supporting literature does not age so fast. Often, customers prefer to retain a familiar UI with controls maintained in their positions to maximize the use of muscle memory when engineers use the tools. This is especially the case for infrequently used products. I am sure you are all familiar with web conferencing tools that keep “improving” and moving all the controls around the desktop leading to frustration for occasional users.

Verified Application Notes?
Application notes should always be treated as “best endeavors;” they are not the same as peer-reviewed published papers. Even with peer review, it can be difficult in complex areas to get two engineers to agree on the same solution to an engineering problem. 

However, with technical information, it is also worth speaking with the product specialist and applications engineer at your supplier, as they are often in the best place to guide if a technical note has been superseded; perhaps they can also offer some useful secrets from insiders, which are off the record. But a designer should use their own training mixed with common sense, research, and theory combined with the information in the application note to gather information in a timely way to make the best possible design choices. 

If, while reading this column, you have had an idea for a useful signal integrity or stackup related application note, please get in contact.   

This column originally appeared in the June 2020 issue of Design007 Magazine.

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2020

The Pulse: Application Notes—Advice for Authors

07-27-2020

Application notes are the key to shedding light on new topics or new products and software tools in an easily digestible form. As both a consumer and an author many application notes, Martyn Gaudion explores various types and how to approach them.

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The Pulse: Communicating Materials From Design to PCB Fabrication

05-12-2020

Designer and fabricator communication—especially for high-speed PCBs—should be a bidirectional “thing.” It is so easy for a designer to say, “Just build this,” and hand over a challenging design to a fabricator who could have performed better with some preliminary conversation or dialog before placing the order. Martyn Gaudion explores communicating materials from PCB design to fabrication.

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2019

The Pulse: Modelled, Measured, Mindful—Closing the SI Loop

07-18-2019

In this woolly world where high-speed signals enter a transmission line with a well-defined shape and emerge at the receiving end eroded and distorted—and at the limits of interpretation by the receiver—it is well worth running simulation to look at the various levers that can be figuratively pulled to help the pulse arrive in a reasonable shape. At speeds up to 2 or 3 GHz, it usually suffices to ensure the transmission line impedance matches the driver and receiver. And a field solver makes light work of the calculation. But push the frequency higher, and other factors come into play.

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2018

The Pulse: The Rough Road to Revelation

03-07-2018

Several years ago, an unsuspecting French yachtsman moored his yacht to the railings of the local harbour. For a very nervous full tide cycle, he awaited to see if the cleats would pull out of the glass fiber hull. Fortunately, the glass held. A yachtsman at high tide isn’t too worried about whether the seabed is rough or smooth, but at low tide, the concern about a sandy or rocky seabed is altogether different. With PCBs, the move to low-loss laminates exposes a similar situation.

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2017

The Pulse: Tangential Thoughts--Loss Tangent Values

12-06-2017

Numbers are fascinating things, and the way they are presented can influence our thinking far more than we would like to admit, with $15.99 seeming like a much better deal than $16. Likewise, a salary of $60,000 sounds better than one of $0.061 million, even though the latter is a larger number. Our brain has been programmed to suppress the importance of numbers to the right of the decimal point. Such is the case with the loss tangent of materials. It is a tiny number and so to our minds looks insignificant, but it has a directly proportional effect on the energy loss suffered by a dielectric.

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2016

Vias, Modeling, and Signal Integrity

12-05-2016

Remember that good modeling can’t fix a bad design. The model can tell you where a design is weak, but if you have committed your design to product, the model can only tell you how it behaves. Some less experienced designers seem to think a better model will fix something that doesn’t work; it won’t. It will only reassure you that the design was bad in the first place.

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2015

Impedance Control, Revisited

06-10-2015

The positives for new fabricators and designers lie in the fact that, even though impedance control may be new to them, there is a wealth of information available. Some of this information is common sense and some is a little counterintuitive. So, this month I’d like to go back to the fundamentals, and even if you are an experienced hand at the subject, it can be worth revisiting the basics from time to time.

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I3: Incident, Instantaneous, Impedance

03-11-2015

In my December 2013 column, I discussed “rooting out the root cause” and how sometimes, the real root cause is hidden when digging for the solution to a problem. In that column, I described how sometimes in an attempt to better correlate measured impedance with modelled impedance, fabricators were tempted to “goal seek” the dielectric constant to reduce the gap between predicted and measured impedance.

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2014

Tolerant of Tolerance?

03-30-2014

Wouldn’t life be great if everything fit together perfectly? There would be no need for tolerance. However, for that to be the case, everything would need to be ideal and without variation...

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2013

Rooting Out the Root Cause

08-31-2013

When your measured trace impedance is significantly different from the calculated/modeled trace impedance, be careful before jumping to conclusions.

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Changing, Yet Changeless

01-16-2013

Like the whack-a-mole game where the moles keep popping up at random after being knocked back into their holes, the same old questions about technical hurdles surrounding signal integrity continue to surface as technology advances.

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2012

Repeatability, Reproducibility and Rising Frequency: The R3 Predicament

08-29-2012

One of the more popular editions of The Pulse in 2011 was the article "Transmission Lines - a Voyage From DC." Starting again from DC and working through the frequency bands, Martyn Gaudion looks at what is realistic to achieve and where economic compromises may need to be made.

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2011

Transmission Lines – a Voyage From Dc – No, Not Washington ...Part 2

08-01-2011

In the second part of this two-part article we continue on our voyage through a transmission line from DC onwards and upwards through the frequency spectrum, step by step exploring the characteristics from very low to ultra high frequencies.

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Transmission Lines – a Voyage From DC – No, Not Washington, Part 1

07-01-2011

In this two-part article I'd like to join you on a voyage through a transmission line from DC onwards and upwards through the frequency spectrum. In Part 1 we trace the impedance from infinity at DC to the GHz region where it reaches the steady state value of its characteristic impedance.

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Crosshatching Compromise

06-16-2011

Sometimes engineering results in some uncomfortable compromises; this is often the case with PCBs as the mathematical methods used by the modelling tools are based on "ideal" physical properties of materials rather than the actual physical materials in use.

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Correlation, Communication, Calibration

05-31-2011

At ElectroTest Expo at Bletchley Park, UK, Martyn Gaudion noticed the extent to which some technologies change, while the overall concepts do not. Prospective customers still ask exactly the same questions as they did 50 years ago: “What’s the bandwidth? Will it work in my application? How accurate?” Followed by the predictable, “How much does it cost?”

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When Is a 10ghz Transmission Line Not a 10ghz Transmission Line?

03-13-2011

'Just as in life, in electronics the only certainty is uncertainty.' -- John Allen Paulos

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Regional Differences – a Voyage of Glass Reinforcement

01-13-2011

Why bulk Er is not the same as local Er

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2010

The Pulse: Laminates Losses and Line Length, Part II

12-20-2010

In the last edition of "The Pulse," we began a discussion on how a modern field solver can help choose the most cost-effective material for a high-frequency application. Last month we looked briefly at the effects of line length and dielectric losses and this month we focus on copper losses; all three are primary drivers for losses.

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The Pulse: Laminates Losses and Line Length, Part I

12-01-2010

The EE creating the "platform spec" and the PCB fabricator responsible for its realisation face an array of materials with a mix of choices: From ease of processing to reliability requirements and signal integrity. For then next two months, "The Pulse" will focus on signal integrity, describing how to use field solvers to select the best materials when trading cost versus SI performance.

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Signal Integrity – the ‘S’ Words

10-01-2010

Three words, or rather, phrases are in the process of entering the vernacular of the PCB industry, albeit one phrase is already familiar, but taking on a different meaning. All start with S and all relate in one way or another to signal integrity.

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All Set to Measure Differential Insertion Loss?

09-13-2010

This column discusses the gradual adaptation necessary for PCB fabricators as more and more silicon families drive the industry toward the requirement for in house measurement of insertion loss.

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Zen and the Art of Accurate Impedance Measurement* – With Apologies to Prisi

08-12-2010

In his 1974 philosophical novel "Zen and the art of Motorcycle maintenance” Robert M. Prisig contrasts his regular and ongoing daily approach to motorcycle maintenance with his friend's alternate view of leaving well alone between annual service center based maintenance. What has this got to do with accurate impedance measurement you may ask? Please read on to discover more…

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New Column: The Pulse

07-14-2010

Polar Instruments CEO Martyn Gaudion will be exploring a number of themes. A major SI topic that is set to grow is the emergence of new silicon families designed to push traditional materials into the multi-gigahertz arena. These new chipsets lift transmission speeds up to a point where signal losses rather than reflections become the predominant concern from an SI perspective.

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