Analog Circuit Design to Go

Let’s pretend for a moment that you’re a design engineer at a company making an industrial control device or a medical instrument.  You’ve got the digital portion of your design pretty well nailed, but there is a 4mA to 20mA process control loop and some isolation issues that you’re a little concerned about.  Although you could design some analog circuits to solve these problems, you’re really a digit-head.  It would take a lot of your time, and you’re not sure you would get it right the first time.  What to do? Analog Devices, Inc. (ADI) has solved your problem.  ADI has recently introduced an expanded version of the company’s Circuits from the Lab^TM reference circuits.  These are not reference designs.  They don’t tell an engineer how to design an entire system.  Rather, they provide lab-tested circuit designs for some common analog circuits that give design engineers problems.  Some examples are ADC drivers, DAC outputs, RF or IF circuits or isolation circuits.  A complete list is available on the ADI website. In addition to the circuit design, ADI also provides circuit documentation test data and is now offering PCB layout files, software device drivers and, in some cases, evaluation hardware.  The purpose is to provide a deeper understanding of the circuit so that an engineer can easily trouble-shoot any glitches that might crop up. It is often said that designing analog circuits involves a bit of black magic.  That’s because unexpected resonances, feedback or other problems can cause an analog circuit to not work properly.  Eliminating those problems can involve hours of bench test work even for an experienced analog engineer.  The purpose of the Circuits from the Lab^TM reference circuits is to eliminate those problems as far as possible and to provide troubleshooting understanding if there should be a problem. The level of integration is increasing for almost all semiconductor end-use products.  NRE costs are rising and the amount of design expertise required has exceeded the scope of the design staffs of all but the largest semiconductor companies or end-use product manufacturers.  In the digital domain, these problems have been addressed by the re-use of blocks of logic, spreading NRE across several designs, and by use of IP (Intellectual Property), blocks of logic designed by small, independent companies.  Semico has been publishing studies about this trend in a series of SoC studies, listed at http://www.semico.com/studies/default.asp. ADI’s reference circuits are, essentially, an extension of these solutions into the analog domain.  By using one of these reference circuits a design engineer is obtaining, for free, a piece of IP; and ADI is spreading the cost of the design over the applications of many of its customers.  This is the continuation of an industry trend, but in the analog domain. Morry Marshall VP Strategic Technologies Semico Research Corp.