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48 DESIGN007 MAGAZINE I JUNE 2020 Feature Interview by the I-Connect007 Editorial Team The I-Connect007 editorial team recently spoke with Kelly Dack about some of the chal- lenges designers face when dealing with app notes and datasheets. Kelly helps clear up some of this data confusion, and he offers advice to younger PCB designers and design engineers who aren't sure whether to trust this data. Barry Matties: Kelly, we often have design ex- perts standing up in front of large crowds of designers and telling them that app notes and datasheets are not reliable. Can you tell us what an app note is from your point of view? What is the difference between an app note and a datasheet? Kelly Dack: The term "app note" is short for "ap- plication note." It documents how the part per- forms in a given application. On the other hand, a datasheet typically documents the physi- cal properties of a part: the size and shape of its available package, its pin assignments, and quite often, a recommended footprint pattern Clearing Up App Note Confusion for soldering the part onto the PCB assembly. Manufacturers publish datasheets for all parts, but not all parts are supplied with app notes. Andy Shaughnessy: Why do some industry lay- out experts consider app notes unreliable? Dack: While I don't disagree with that perspec- tive from some of the expert designers of the world, I am aware of the manufacturer's re- sponsibility to define their product and the per- formance of their products responsibly in these app notes. I want to be able to trust them, but I've read enough horror stories told by our in- dustry experts to know that changing the cir- cumstances—working a complex part or chip- set into a layout which varies greatly from the app note's surface topology or materials stack- up—can lead to some gruesome results. There are so many stories regarding app notes and even datasheets being unreliable that I can see how it can be confusing to a new PCB engineer. Shaughnessy: How should an inexperienced PCB engineer move forward if they cannot trust an app note? Kelly Dack

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