Lee Ritchey Returns to AltiumLive with 32 Gbps Design Class
Lee Ritchey was one of the instructors for last year’s inaugural AltiumLive event, which drew hundreds of PCB designers. Now, Lee is back, teaching a high-speed design class at next week’s AltiumLive in San Diego. That class is sold-out, but you can catch Lee teaching the same class at the January AltiumLive event in Germany.
I asked Lee to explain what he plans to cover in this course, and why PCB designers and design engineers should consider attending one of the events.
Andy Shaughnessy: Lee, why don’t you tell us about what you're teaching this year at AltiumLive.
Lee Ritchey: Well the course is a one-day seminar, and the title is “Getting to 32 Gigabits Per Second.” We're trying to go up the speed curve again. It's not a question of whether we need to; it's because we can. Many in my class are already doing that. Not everybody is, but lots of people are doing PCI Express, which is more or less the same technology.
Ritchey: And so I realize that in my two-day course, I actually have to cover that topic, because people are afraid of it, like it’s something mysterious. The goal is to take some of the mystery out of that. Because—and I may regret saying this—but it's not as hard as it looks. But you can always say that if you've already done it, right?
Shaughnessy: That’s how it goes.
Ritchey: I mean, as you well know, every year we push the envelope, and so my course is sometimes modified twice a year. What's new? We thought, what the heck? We might as well take this thing and dance it around to the designer. I mean, the engineers are getting a lot of this, the designers not so much. You're not surprised by this, I'm sure. There are lots of myths in circulation that someone needs me to take care of. I kind of think that's my job.
Shaughnessy: Right. What are some of the challenges you run into at that level?
Ritchey: Well, as you might guess, you have to have a sharp pencil. For the last four or five years, if you went to DesignCon, you'd see that we were doing everything we know to reduce the loss in the laminates. The reason for that was that the SERDES were not all that great.
And in between times when we have struggled like crazy to get lower-lost laminates, the people who design the ICs have made them better and better and better. Let's say six or seven years ago, we had to figure out how to deal with only an allowance of 10 db of loss. Which put us right on the edge all the time. Now the latest round of SERDES from companies like Xilinx are able to deal with 38 db of loss, which is massively different. And so now the struggle for below loss is not at the top anymore. A thing called skew is. Skew is a misalignment of the two edges as they come up and enter the receiver.
Ritchey: And it could be caused by two traces not being the same length, but our designers are good at that. This is something that took the industry by surprise: The glass weave, if it’s not the correct weave, will cause that problem. With E glass, there are two styles that have been used historically for 3 and 4 mil cores (106 and 1080, respectively). And the spec on them is so loose almost anything if you have the right number threads you can call it that. That’s not enough anymore. So what we need is what we call flat glass, meaning that the fibers in the glass have been spread out so that they are uniform across the surface. That happens right now, but not for signal integrity, but for laser drilling. And laser drilling has not as high a requirement as we do for signal integrity. Are you familiar with the problem with laser drilling on glass cloth?
Shaughnessy: Well, I know it’s a hassle.
Ritchey: If you look at a piece of glass cloth that goes into a laminate, normally you'll see that there are glass bundles that are more or less tightly twisted and in between there will be openings that are all resin. And if you're not doing high speed, nobody cares. If you are doing real high-speed signals and your trace is on top of one of those glass bundles, you get one dielectric constant if it’s in between where you are, and in all resin you get a different one. And those result in two very different velocities such that the one that is on the glass bubble is slower than the one that is in the resin.
And it's so bad that at 10 gigabits we have links that simply will never work if you don't have the right glass. By the way, I'm just reviewing a design guide from one of these houses that does contract board layout. And it said to let the fabricator do your stackup. That just becomes a recipe for failure.
Shaughnessy: They can't possibly know everything that they need to know to do a good stackup.
Ritchey: Well at the most fundamental level, very few of them get the impedance right. In fact I just reviewed a stackup from a client who got a test report from a fabricator saying that all the trace layers were 50 ohms. It was a measured report. I've taught the customers to put their own test traces in and measure, and two of the signal layers were 44 ohms. They should have been 50, and the test report said they were 50. I took the fabricator stackup and went through the field solver and it told me it would be 44 ohms, so the fabricator faked everything.
Ritchey: I'm trying to be polite here. It’s unconscionable how badly that was done. Now this particular fabricator, I have a history with them and if you challenge them, here’s the kind of response you get. “Well, nobody ever checks so it must not matter.” It must not make any difference, because they're not checking. What's really happening is they're having trouble; the customer is having trouble with these boards being marginal and they don't know why. But that's unconscionable for someone to do that. The guy looked me in the eye with a straight face.
Shaughnessy: You could write another book just detailing horror stories.
Ritchey: I don't have enough room! Now, this particular vendor has this history for the last 15 to 20 years. I've lost count how many times I've had to troubleshoot where they've done it wrong. But the engineers let them do it, so you could argue that that's what the engineers deserve for not paying attention.
Shaughnessy: So you taught a class at AltiumLive last year. What did you think of that event? I heard they had more than 200 designers attending, and we never see that many designers even at designer events. Plus many of the courses had nothing to do with Altium tools.
Ritchey: You know, I encouraged them to do that. There isn't enough of that being offered to designers, and I said, “You’ve got all of these people together, so offer them something besides how they use your tool.” I got that from working with engineers in Europe; the engineers complain all the time that they don't have access to good information to keep up with the state of the art. And that's why I'm still working. That's why Rick Hartley is still working. We're both sold out!
Shaughnessy: It’s as if Altium is trying to facilitate or take the place of organizations like IPC, because sometimes IPC doesn't really seem to know what to do with designers, and they are a hard segment to monetize.
Ritchey: Well, right. IPC used to be good at it. I used to do classes at IPC. I don't know why, but it’s not that way anymore. I have some theories but I'm going to keep them to myself. But whoever is running Altium now is actually adding a lot of value. I just taught a class at Sandia and about half of them are switching to Altium. And they are switching because they don't have big complex designs, and so to spend $100,000 a year on a big complex tool is not a bargain. And the big guys won't accommodate that.
Shaughnessy: Did the “big three” EDA companies give up on that market?
Ritchey: Yes they have. I have a good idea why. For a very long time, if you wanted a complex product you had to have a complex boards and you needed a tool to go with it. Think about how much stuff you get in one integrated circuit now. I have a graphic I use in my class. I show a terabit router we did in 2002. It weighed 350 pounds, with 61 circuit boards. In 2007 we did that with one board weighing 22 pounds. So you don't need the monster tools anymore to make most products.
Shaughnessy: That’s nuts…in just five years.
Ritchey: It’s the same problem with SI tools. You don't use them every day and if you have to drop 100 grand for something you use every six months, that's hard to do.
Shaughnessy: Are you teaching at both AltiumLive events this year?
Ritchey: Yes, San Diego and then Munich in January. I’m doing the same course in both places. Within a week of opening, the class sold out. They are paying attention more, but they don't really have a choice. We are designing 56 gigabits in the next line of products.
Shaughnessy: Are you seeing anything related to 5G yet?
Ritchey: Supporting 5G is what we have to do in the routers, and the switches, and the Internet. And the boxes we've done with 28 gigabits per second are doing 5G. Which really means just hellishly higher bandwidths. My partner John Zasio and I have decided that when they ask us for 100 gigabits per second, we're retiring! That’s damn microwave.
Shaughnessy: Right. Yeah, that's something else. So, any thoughts on the long lead times on these components, and some laminates? Some of these EMS companies are having to stockpile certain components.
Ritchey: Well here's a piece of news we got about a month ago, and I don't know what we're going to do about it. The suppliers of our ceramic capacitor packages will no longer make the 0603 package. Because the cell phone industry is buying so many 0402s they can't change their line over. How many thousands of boards are designed with 0603s on them? Most of mine.
Shaughnessy: Never a dull moment. Lee, is there anything else you want to talk about that we might have missed?
Ritchey: The big deal is, of course, running up the speed curve and that is why I'm doing this course. It’s all about different signaling at high data rates which are invading everyone's products. Pretty much every level you want to look at, this is showing up. The HDMI cable on your TV, the USB connection, all that stuff.
Shaughnessy: That's great. Well, thanks for your time, Lee. I’ll see you in San Diego.
Ritchey: Thanks for the opportunity, Andy.
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