Wild River ISI-56 Platform Accelerates SerDes Testing

Estimated reading time: 13 minutes

Neves: The issue I have with the connector companies is that you have two products: you have good products and bad products, but what you have for both of those is they generally don’t know how to use their own products (laughs). If you rely on most of the connector companies to help you do your electrical optimization into the PCB, you end up with a horrible result. There are exceptions to that. Molex is pretty good, and Samtec is very good, but most of the other connector companies relegate the customer optimization to junior engineers that don’t have the experience or time to get it right. I’ll deal with a connector company and they’ll throw some junior engineer who’s just learned HFSS, and I look at the result and I think, “You haven’t even begun to understand this problem. That poor young guy, or gal, is suffering under a lack of technical leadership.” Most of the connector companies are befuddled with that right now, and the encrypted HFSS model approach with poor stackup design, along with not setting up HFSS correctly is killing them.  

I know that my statements are pretty strong, but when you think about this, we’re trying to achieve stellar signal integrity past 70 gigahertz. It’s a very difficult game. Everything has to be done perfectly, and you have to understand the problem. It’s not a compromising or easy space to be in.

Shaughnessy: It’s good to tell it like it is. So, who is the typical audience for the ISI-56? Who is typically going to say, “I’ve got to have this?” Is it for any specific segment?

Neves: Really, it’s anybody who’s developing SerDes and characterizing SerDes, both at the silicon level and the intellectual property level. Synopsys is a great customer, and Cisco, NVIDIA, etc. But it’s also OEMs, SerDes manufacturers, people who are buying SerDes to evaluate them, and the incoming quality control folks. If they’re buying a SerDes, they can use our test platforms to verify, not just whether it meets the performance, but also to say, “What’s the true performance of it?”

Shaughnessy: Right. SerDes seems to be a big thing. Barry Olney writes about SerDes in his column sometimes and he’ll get thousands of reads right away. Everybody’s hungry for information about SerDes.

Neves: That’s the fundamental of the physical level. That’s where the actual 1s and 0s, the actual data is occurring—at its physical level. That’s fundamental to the performance metric of the system.

Shaughnessy: So, for the ISI-56, is there a learning curve for this? Can a signal integrity engineer just pretty much jump on it and hit the ground running?

Neves: We have measured S-parameters that are ready to be simulated. I run a one-hour training class. What I like about the product and our test fixtures is that we throw out a lot of energy on the front end in an integrated solution. We have a Keysight ADS simulation kit that we give our customers. We have measured S-parameters so they can run that in MATLAB. We have a comprehensive user’s manual. We have graphs. Recently we came up with COM metrics for all the channels and we provided that as a report. We have COM metrics for 32G NRZ, 56G PAM4. COM is a figure of merit for those data rates, so that’s really helpful. We also have good application support. The WRT product training that we do really helps our customers. We don’t really get a lot of application issues after the training, so there’s no real learning curve.

Shaughnessy: That’s great. Is there anything you want to add? Anything we haven’t covered?

Neves: When you’re deciding on a solution, there are a host of things that are really important. The homogeneity of the platform is important. The materials that you select when you build your test fixture—that’s called weave—there’s been a lot of discussion on that. We talked about launch integrity, which is measured by TDR impedance. The return loss is measured by a VNA and what that return loss looks like. Again, there are two other solutions on the market right now. One is a USB solution that I would consider poor to very poor signal integrity. It’s magnetically introduced ISI, and I don’t really know how the industry is using that platform effectively because the signal integrity is poor. It’s convenient, it’s USB-controlled, and you can control the channel loss with a USB computer, but it doesn’t relate to how a backplane works with dielectric and skin effect losses.

The Keysight platform was released fairly recently, and our test platform is twice as good if you compare the S-parameters that they published versus the ones that we published. Their platform is probably good out to about 10, 12 gigabits per second, certainly not 56G PAM4 as they claim. You just have to look at the power spectral density and the Nyquist. I don’t want to get too technical with that, but these platforms either meet the requirements or they don’t. It’s not really that complicated.

Shaughnessy: That’s great. So, what’s next? What are you guys working on for 2021?

Neves: We’re working on the complete family of 70-gigahertz test fixtures. Then there’s a company working on 1.35-mm connectors up to 90 gigahertz, and we’ll be working on that Q4 2021. Then we’re going to work on some test fixtures that torture the SerDes in some very novel ways, introducing mode issues and resonance. We’re coming up with a whole series of products to do that in Q2 of 2021. We’re getting calls right now, as I mentioned earlier, from our customer base going up to 224 G. The next thing that’s happening in the industry is that mil-aero is coming on strong. They’re trying to do PCIe gen 4 and the military’s problem is pretty intense because they have to build Class 2- and 3-compliant systems. Their signal integrity is not as demanding as the commercial, but let me give you an example. With some of the stuff that my company makes, if you put it in a tank and a tank round went off, some of the compression mounted connectors might not work. Their problem is pretty challenging, actually. We’re getting a lot of business right now from the mil-aero folks because their signal integrity requirements have gotten pretty extreme in the last year or two. They’re going up to 32 G, and they’ve been at 10 G with issues, so this is a big step up for them.

Shaughnessy: That’s a good segment to be in. The checks don’t bounce from them.

Neves: It’s the circle of life, right? My company’s doing well, so I pay too much in taxes, but that money goes to the federal government. The federal government then pays mil-aerospace companies and then the mil-aerospace companies give me that money back again. It’s the circle of life (laughs)!

Shaughnessy: That’s a great point to end on! Thanks for talking with me, Al.

Neves: It’s always a pleasure talking with you, Andy. I hope we can get together next year.

 

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