Reading time ( words)
At DesignCon 2018, I ran into Mentor’s Fadi Deek, the author of both of Mentor’s I-007eBooks, the new The Printed Circuit Designer’s Guide to Power Integrity by Example and The Printed Circuit Designer’s Guide to Signal Integrity by Example, which were published in 2017. We sat down and discussed how the idea for the books came about, as well as some of the power integrity challenges facing PCB designers and engineers.
Fadi is quite a multitasker. While he was writing the second book, his wife had a baby, he finished working on his PhD, and the family moved into a new house. I imagine Fadi was glad to just have a chance to sit down and chat at a trade show.
Andy Shaughnessy: I'm speaking with Fadi Deek, corporate applications engineer for Mentor‘s high- speed design group, and the author of a couple of I-Connect007 books. Fadi, I edited your book, and it was really well written. Nice to finally meet you.
Fadi Deek: Thank you, Andy. Pleasure to meet you too, and thanks for having me today. It's a pleasure to meet you in person and talk about these books a bit.
Shaughnessy: Well, tell us about the newest book, Power Integrity by Example. When did you all get the idea of writing this book? Or were you roped into writing it [laughs]?
Deek: The idea began at the end of 2016. We were thinking of ways to use HyperLynx, and its ease of use, and how it can really transfer the idea to engineers in a very simple, clear manner. In the industry, there are lots of books that discuss the theory about signal integrity and power integrity issues, but they lack a lot of the good examples, the practical designs, that can help engineers understand the issues a lot more. We started with that idea, and then we just started writing and seeing what the most important issues were facing customers right now. As a customer support engineer, I work with customers all the time. I have a really good idea about the issues our customers face when they use high- speed design analysis tools. That's basically how we wrote the outline of the topics.
Shaughnessy: There are a lot of books out there that are written at a higher level of theory, but they don't necessarily help the designer or design engineer on the next job. These examples that you had in the book were real-life examples. Were these some of the problems that you faced as part of your job?
Deek: Certainly. There are examples we saw all of our customers working on. We started with the basic things in order to explain the fundamentals. There's a significant amount of theory in there. We didn't exclude that at all. However, we used theory to help explain what to expect from each design, from each practical design example. By using that theoretical knowledge, we can now implement that knowledge we have in order to anticipate what the results are, even before we hit the simulation button.
Shaughnessy: Are you seeing more people using simulation? I'll ask designers at a show like this if they use simulation, and a lot of them still aren't doing it, but it seems to be growing somewhat.
Deek: Yes, I totally agree. We see that growing more and more. With faster designs requiring faster edge rates, simulation has been the tool to get the design working well before going to building a prototype. It's increasing more and more, and part of the goal of these books are to help engineers try to expect the results before they run the simulations. Even though I'm part of a simulation company that does software, we don't want the customer to blindly run a simulation and just accept whatever they see. There might be some things that they have missed in setting up the design. We want them to be intelligent users of the tool. This will help them explain what they're seeing before they even run a simulation.
Shaughnessy: Right. It seems to be that a lot more people are paying attention to power integrity than they were in the not-too-distant past, because everybody was busy putting out signal integrity fires for so long. Are you seeing a lot more interest in taking on power integrity?
Deek: Yes, as you said, signal integrity was the most popular simulation or analysis topic. People were not as concerned about power integrity issues. Popularity began growing since the late ‘90s and early 2000s. That's when a few power integrity analysis tools started showing up. Right now, there is a need for a good, solid understanding of power integrity principles, and the fundamentals that guide how the PDN [power distribution network] interacts with the different components; how the signal and the return current passing through that PDN would interact with stitching vias, with the coupling capacitors; and how it could affect other signal vias sitting at a different location of the board. With the power integrity book, we discussed topics ranging from understanding the impedance of the cavity, explaining what each peak and dip in the impedance profile of that cavity means, and why it behaves that way. Then we start building on the bare cavity by adding the different elements of the PDN, which usually involves a set of the coupling capacitors, stitching vias, even adding the volt regulator model and seeing its effects and understanding at which frequency range each of those elements will tune the impedance profile of the cavity.
Shaughnessy: That's one of the interesting things, if you don't get the power right, it can even end up screwing up the things downstream like signal integrity and all the rest.
Deek: Right. Even though it's called power integrity, really it sees its benefit in what people might also call signal integrity. It's the same thing. You can see some crosstalk and coupling happening due to a poor design of the power distribution network, or the PDN.
Shaughnessy: So, are you going to write any more books?
Deek: Hopefully if the opportunity comes. There are a few more topics we'd like to present and help explain more, and certainly, we’ll use a variety of examples in order to explain the principles and theories. A lot of people who are reading these books just don't have an opportunity to see demos that come up from real life in the industry.
Shaughnessy: Is there anything else you want to mention?
Deek: Well, I would like to thank I-Connect007 again for the opportunity. It was a pleasure writing these books and working with the team.
Shaughnessy: Thank you, Fadi.
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