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Design007-June2020

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12 DESIGN007 MAGAZINE I JUNE 2020 Rick Hartley: I start all my classes with a com- ment I heard Lee Ritchey make 27 or 28 years ago, that app notes produced by IC manufac- turers should be assumed wrong until prov- en right. A few people questioned him and said, "They're not all wrong." Lee responded, "I didn't say that. I'm telling you that enough of them are wrong that you should not as- sume they're right; you should assume the other way and prove they're right if you be- lieve they are." When Lee made the statement, I giggled, and he asked, "Do you disagree with me?" I said, "No. I've believed that for some time, and I'm glad to see there are two of us." And then we both laughed. Dan Beeker is the one who made me understand. I had always had heartburn with app notes, but I never thought about why until I attended one of his class- es. Somebody asked Dan, "What's wrong with them?" because he made a similar comment in the class that app notes aren't always good advice. He said, "App engineers all understand circuit theory. They all have a circuit back- ground and can talk about schematics all day long, and they're right 99% of the time. What Feature Interview by the I-Connect007 Editorial Team If you're a PCB designer or design engineer, you're probably familiar with app notes—doc- uments produced by the chip makers and oth- er suppliers that are supposed to provide de- sign teams with vital information for creating better circuit boards. But do app notes do what they're supposed to do? There's a disconnect in the design segment. Some designers say they follow app notes ev- ery time, but a growing number of designers approach app notes with a wary eye. Many of the leading voices in the design communi- ty have been advising designers not to rely on app notes without running the numbers first. We decided to ask PCB design instructors Rick Hartley and Dan Beeker to help us shine a light on this issue. Andy Shaughnessy: A couple of years ago, while Rick was doing a class, somebody in the class stood up and said, "We're required to follow the app notes." Rick, you almost had a heart attack. What is the Proper Role of App Notes?

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