Beyond Design: Mastering “Black Magic” with Howard Johnson’s Seminars


Reading time ( words)

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 more than 20 years, at Oxford University and worldwide and is arguably the most practical and enlightening course on high-speed—black magic—ever delivered. Howard’s unique explicatory presentation style creates an unforgettable picture of signal propagation by practical example. If you want to gain some of his enthusiasm and master the art of high-speed design, then the collection is a must-have.

I recently had the opportunity to review all three of the seminars in this collection, a total of 36 hours of viewing time. When presented with a selection of three seminars, to watch, I guess it is only natural to want to start with the more advanced topic. But I am glad that I forced myself to start at the beginning to refresh the basics before moving on to the more complex issues. It is amazing how much I either did not know or had simply forgotten over the years. Or maybe I’ve just killed too many brain cells along the way!

I know that during my own courses, there is always one guy at the back who falls asleep. And strangely enough, he is always the one to give bad feedback, probably because he didn’t learn anything. But I guarantee that you will be on the edge of your seat throughout Howard’s entire seminar series. His dynamic teaching style ensures you feel like you are not just a part of the audience—you are actually participating in the demonstrations. The picture that Howard paints leaves a lasting impression on how electromagnetic fields propagate and how they induce voltages and current (crosstalk) into nearby signals. The following is a section-by-section discussion of the course contents.

1. High-Speed Digital Design

Engineers and PCB designers need to understand electromagnetic theory, appreciate how coupling occurs and why energy moves to unintended, sensitive parts of the circuits. A logic schematic diagram masks details crucial to the operation of unintentional signal pathways vital to your understanding of signal performance, crosstalk and EMI. To realize these factors, one must uncover the hidden schematic, operating behind the logic diagram, to reveal the parasitic elements that affect the circuit. These parasitics are invisible to the uninitiated, but become very clear once skillfully explained in detail. You will gain new insight into what really happens in the circuitry.

Also, understanding the frequency band that really matters for digital design is very important. Traditionally, we used 0.35/Tr (where Tr is the rise time in ps) for the upper bandwidth. However, Howard recommends using an upper knee frequency of 0.5/Tr, which forms a crude, but useful, translation between time and frequency domains. So for instance, if the rise time is 500ps, which is typical these days, then the upper bandwidth is actually 1GHz regardless of the clock frequency. Furthermore, the constant improvement in the IC process reduces die size which speeds-up the rising edge. This in turn pushes the knee frequency up, causing signal overshooting and ringing.

To read this entire article, which appeared in the June 2016 issue of The PCB Design Magazine, click here.

Share


Suggested Items

Excerpt: The Printed Circuit Designer’s Guide to…Flex and Rigid-Flex Fundamentals

06/20/2018 | Dave Lackey and Anaya Vardya, American Standard Circuits
The design process is arguably the most important part of the flex circuit procurement process. The decisions made in the design process will have a lasting impact, for better or worse, throughout the manufacturing cycle. In advance of providing important details about the actual construction of the flex circuit, it is of value to provide some sort of understanding of the expected use environment for the finished product.

Faster Board Speeds Demand Constraint-Driven Design

06/19/2018 | Ralf Bruening, Zuken
Using powerful constraint techniques can be a double-edged sword. While the design process is made much safer by including constraints, it is all too easy to over-constrain the design and make it impossible to complete routing and placement. Even paper design guidelines can make products uneconomic to produce unless a great deal of engineering knowledge is applied during the design.

Making the Most of PCB Materials for 5G Microwave and mmWave Amps

06/13/2018 | John Coonrod, Rogers Corporation
Ready or not, 5G is coming, and it will require the right circuit materials for many different types of high-frequency circuits, including power amplifiers. 5G represents the latest and greatest in wireless technology, and it will be challenging to design and fabricate, starting with the circuit board materials, because it will operate across many different frequencies, such as 6 GHz and below, as well as at millimeter-wave frequencies (typically 30 GHz and above).



Copyright © 2018 I-Connect007. All rights reserved.