When is PCB design like a popular video game?

When is electronics work much like a popular video game? I'll wait... De-de-de-deeee... Give up? When it's designing an analog electronics circuit board! Laying out an analog electronics board, placing the individual devices is MUCH like playing a game of Tetris. Unlike digital layout, where "if the traces are all connected, it'll work*"; where one can place the components more or less anywhere regardless of trace length, placement on the board, etc. pretty much anything goes and the board will fire up.

In analog the goal is to move the components around on the board, rotating, moving again, minimizing the trace length between devices, keeping track of power, "naught 0", ground... This means that components can wind up being at odd angles to each other (minimizing inductor coupling or components and traces having inductive or capacitive coupling), some devices closer to each other than others (the devices around an op amp), all kinds of things that might look "messy or odd", of course following the standard PCB rules; pad sizes appropriate to manufacturing ability. If you think "all components should be lined up very neatly and look *nice*, you need to study analog PCB design more closely. If you've been in an airplane, looking at the layout of roads and cities thinking " That's a nice square symmetrical board layout, you're probably a PCB layout or design engineer in digital". However, look at the layout of a town in the New England area, like Boston (my home area) where they basically paved over horse trails, you think "That must be an analog board", you're on the right track...

Analog layout isn't a "black art" as some would have you believe; it's just that the "minor rules" are learned over time, with study in the area and if not followed, do so at your own peril. The PCB's must be designed to minimize EMI/RFI, paying close attention to the hundreds of little "antennas" and "capacitors" that are formed all over the PCB. Doing this, while also making sure that you can manufacture 100K of the boards, quickly, with none of the various issues that can creep in (placing components too close without the proper soldermask to keep them from turning into a "clump" is always fun).

There are some brilliant books (books!) out there on high speed design with much information that is applicable to most analog designs, and should not be ignored. If you're up for the challenge, look up many of the datasheets and data-books from Burr-Brown/National/Texas Instruments. There's priceless information in these books that one would be foolish to not look up. In my early days of design, doing low-noise/high gain amplifiers for electron microscopes would have been impossible without the information from Burr-Brown, such as explanations of "a resistor with capacitance" and how to mitigate it is always a balancing act. Analog/Linear Tech also have some fantastic white papers in just about every aspect of analog design. TI has some brilliant papers as well as videos!

Next time you're looking for some PCB design work, analog, mixed signal, digital and the people you've hired have put the input resistor on one end of the board and it's associated op amp input across the board, give me a call... (that, BTW, is a real world example of some of the designs I've seen...)

*Work, in this case, means the board fires up and everything is doing what is expected. Until you start doing FCC, EMI/RFI testing...

As always, Peace!

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Mike Tripoli

SCARY Design