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Design007-May2021

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20 DESIGN007 MAGAZINE I MAY 2021 then you need the series terminators to pre- vent reflections on the long data lines. Matties: Over the years, expert designers have told us that with high-speed design, there really is no substitute for experience. How does a young design engineer become an expert at DDR? Hartley: ey make a lot of mistakes. I certainly did early on. Olney: My wife says to me when I'm writing my articles, "Why are you giving all of your secrets away?" I say, "Because nobody can remem- ber them. I can't remember them." (Laughs) You've got to try to recall it all. Hartley: My wife asked me that about the classes I do, "Why are you telling everybody all the stuff you know?" I told her, "Well, I'm not going to live forever, for one thing, and I want the world to get as much of this as we can give them." Matties: Is there a role for EDA tools that helps in this regard? When does the tool come in and really help take the heavy load? Olney: First, you need to understand the tech- nology behind it. You can't just hand someone a simulation tool and expect them to simulate a board. ey have to know how it all works and understand it. It is the same with routing, placement, and positioning power supplies— they have to understand why they're doing cer- tain things. You have to teach them, but it's also experiences—you have to gain the knowledge over time. It doesn't matter how good your tool is if you don't know how to drive it. Hartley: To make matters worse, as we all know, there are not more than two univer- sities on the planet that teach circuit board design. Young people coming out of school have no understanding of this stuff, and young engineers are being pushed into board design. In our day, you could choose a path. Today, almost all the young engineers are doing the circuit design and the board design, and they're thrown into it with no knowledge of the things Barry is talking about; they've got to figure it out quickly. Shaughnessy: Could you guys teach a new EE how to do DDR design in one month? Or six months? Hartley: I think it is possible within one design cycle. What do you think, Barry? Olney: Yes, I've trained many PCB designers. I have taught a lot of people how to design high- speed boards and they usually become excel- lent aer a year; I check their work and they make no mistakes; they just follow the process. ey probably need at least two design cycles to be a proficient independent designer, as each board is different. Hartley: If you want to learn the whole high- speed design philosophy, it takes about a year. But if you just want to learn how to design DDR, you will have that down in one or two design cycles. Olney: If you want to simulate it, that's a differ- ent story altogether as there are a lot of issues. Models are the biggest issue, and I've actually developed soware that can help me, in par- You can't just hand someone a simulation tool and expect them to simulate a board. They have to know how it all works and understand it.

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