Resourcefulness, or why good engineers (and good cooks) use the best available components.
Q.  Which (amplifier/switch/converter) is best in a (mobile phone/strain gauge/medical ultrasound system)?


A.   Whichever is most efficient and cost-effective, no matter what it was originally designed for. When choosing an IC, ask what it does, and how well it will work, not whether it was designed for the type of system you are building.

While at the butchers last week to buy ground beef for spaghetti bolognaise, I noticed some cheap stewing venison. So I purchased some, minced it, and made a delicious "spaghetti alla salsa di cervo." Later that week "chile con venado" was equally successful.

As engineers we must use the best available resources to design our systems. The word engineer is derived from the Latin "ingenium," which means ingenious, i.e. resourceful. Bolognaise and chili recipes specify beef, but venison has less fat and improves the flavor.

It is unwise to avoid an IC because its data sheet does not specify a particular application. Recently, we conducted research to find out why some companies that bought a lot of our analog switches for handsets did not buy one particular type which was more ideally suited in both performance and price. The switches that were selling listed "handsets" among possible applications, but the data sheet of the better suited switch did not, so it was not considered. This is not good engineering.

Asking fundamental questions helps us to choose components (ingredients) which, though not intended or specified for our application, are actually well-suited to it.

For example, a useful component that can be easily overlooked is the AD8210. Described as a "current shunt monitor" its data sheet lists its applications as "current sensing" followed by six automotive current sensing tasks. Potential users can be forgiven for assuming that the AD8210 is simply an automotive current sensor. In fact, the AD8210 is an in-amp with a CMR from 0 to +65 V when operated with a single +5 V supply. Developed for automotive high-side current measurement it is valuable wherever a small signal with a high positive commonmode voltage and reasonably low source impedance must be measured. It has been used successfully in industrial instrumentation, avionics, battery chargers and innumerable other applications, but only by engineers who see past the description on its data sheet.

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James Bryant Offers Intrigue, Interest and Technological Troubleshooting Ideas... engineer, applications manager, philosopher, humorist, columnist and radio ham (G4CLF), only a man with such an eclectic dossier could make the often drab world of semiconductors come to life with such color and imagination. James Bryant

For More Information:

AD8210 High Voltage Current Sense Amplifier (pdf, 13,874 bytes)

AN-815 Application Note

Designer's Guide to In-Amps

Current Sense Amplifiers

Ground Current Measurement (pdf)

How to Cook Venison

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