Reading time ( words)
It’s September, which means trade show season is beginning. The 2019 AltiumLive PCB Design Summit will be here before you know it, taking place October 9-11 in San Diego, California. Teledyne LeCroy’s Eric Bogatin, the “signal integrity evangelist,” will be giving a keynote presentation titled “Breaking Bad: A Downside of Open Source Designs.” I asked Eric to give us a preview of his presentation and discuss some of the biggest design challenges he sees today.
Andy Shaughnessy: I like the title of your keynote. Some people in the industry see open-source technology as a kind of panacea. Give us a preview of your presentation. What do you hope attendees take away from your presentation?
Eric Bogatin: The title was Judy Warner’s idea (the director of community engagement for Altium). The point I will emphasize is that just because someone posts a design on the internet and it works does not mean that it is a good design and one you should replicate or learn habits from.
In particular, we will look at the design for an Arduino Uno board that is popular on the internet. All of the CAD files are open-source. However, the design violates almost every one of the design rules that I recommend. You could build the circuit on a solderless breadboard, and it would work (most of the time), but it is not easily scalable in clock frequency.
In my class at the University of Colorado Boulder, we measure the switching noise on this commercial board. It can be in the 1 V level or more for a 5 V logic level. Then, my students redesign the board as a two-layer board, but it’s designed well. The switching noise levels are as low as 0.1 V or less in many cases. There are no cost additions. I will talk about this experience and the good design principles everyone should follow for two-layer boards.
Shaughnessy: What do you think are some of the biggest challenges that designers face today?
Bogatin: Most products have signal integrity (SI), power integrity (PI), and electromagnetic interference (EMI) problems. These lurk in the ideal wires and white spaces of the schematic. If you don’t understand how the electromagnetic fields interact with the physical design of the interconnect, you cannot understand how the physical design features of your product influence the design.
Layout engineers need to understand some SI/PI and EMI principles or at least enough to know when to question their layout habits. They need to learn to communicate clearly with hardware engineers and to sense when a hardware engineer doesn’t know what they are talking about. Engineering is a moving target. If you don’t constantly refresh your knowledge base, you will be left behind. That’s why reading well-curated websites and attending conferences, classes, and webinars is so important.
Shaughnessy: Tell us about the courses you teach at UC Boulder. Do you teach PCB design, or is it mainly engineering classes? I know it has been tough to get PCB design into the university system.
Bogatin: I teach two courses. One class is a graduate-level course on SI based on my textbook. It trains students in the essentials of transmission lines and S-parameters. The second course is a “Practical PCB Design and Manufacture” class, which is very hands-on. I train students how to go from a back-of-the-napkin sketch to a working widget in their hands. It’s not just pushing the layout tool; it’s also about finding parts, documentation, design for bring-up and test, and how to measure and troubleshoot their boards using scopes and other lab instruments. I teach a mix of undergraduate seniors and graduate students.
Shaughnessy: I notice you have a lot of webinars and other resources at the Signal Integrity Academy. How’s the academy going? What are the most popular classes you teach? I know the essential principles course always did well.
Bogatin: The SI Academy is doing very well. We have about 200 hours of video content that is streamed and available 24/7. Most of the content focuses on best design practices. As you mentioned, the most popular class by far is the essential principles class; it has been viewed more than 20,000 times by various engineers and is based on my textbook.
All of the live classes I used to do around the world were recorded and posted on the SI Academy website. Subscriptions are available for individuals or entire companies. You can get a complimentary three-month subscription by asking your local Teledyne LeCroy sales representative.
These days, I am focusing on the best measurement practices. When I do live webinars or lectures, I always bring my scope or other instrument and demonstrate how to do measurements the right way, avoid artifacts, and interpret the results using the essential SI and PI principles. And best of all, all of my live events are now always free.
Shaughnessy: Are you working on another book?
Bogatin: I am actually working on two books. The first one is with Artech on the fundamentals of transmission lines, covering principles, design, and characterization with a TDR. The second book is a textbook based on my PCB course.
Shaughnessy: Have you come up with any new catchphrases like, “It depends”? I hear other instructors quoting you in their classes, and, “It depends,” seems to have caught on.
Bogatin: I have a bunch of common phrases I use in my classes and lectures, like:
- The fastest way to fix a problem is to find the root cause; if you have the wrong root cause, you will only fix your problem based on pure luck
- Practice situational awareness; be aware of what your instrument really measures, what its limitations are, and how close to the DUT performance your instrument is
I have a bunch more of these one-line rules I compiled into a booklet called Bogatin’s Book of Lists. I will be giving them out at the AltiumLive to anyone who stops by and says hi.
Shaughnessy: Is there anything else you’d like to add?
Bogatin: I encourage anyone who is interested to talk to me at AltiumLive. I look forward to meeting new friends.
Shaughnessy: Thanks for talking with me, Eric.
Bogatin: Thank you, Andy.