Analog alive and well but gets digital boost

Electronic News, March 2, 1998 by Kerry Lacanette

Question: The death of analog has been predicted---even announced for years. Now analog is getting increased attention as the critical element in the next generation of information appliances and other consumer electronic products. What happened?

Answer: Analog is alive and growing, and that's never been as obvious as it is today. The world is analog. Information is analog. Digital techniques are great at processing huge amounts of data, and we'll continue to need more and more of that, but the interface with the real world is, and always has been analog. As a result, analog is stronger than ever.

However, major changes are taking place. Analog is losing its purity. Traditional analog circuits like amplifiers, temperature sensors, and voltage regulators increasingly have digital input or output pins for shutdown, output enable, microprocessor reset, or communication. Mixed-signal techniques for trimming, self-calibration, and noise rejection are improving analog performance, reducing prices, and making real analog compatible with digital processes for system chips. As the mixed-signal system-on-a-chip becomes more widespread, the analog environment will change even more. So, while analog is growing at a rapid pace, pure analog functions may not grow as quickly as those that take advantage of digital techniques. It's not just analog anymore.

Q.: Does this mean that analog will soon be found only on big, mixed-signal system chips?

A.: Absolutely not. It's true that a system-on-a-chip makes a system designer's life better. It speeds system development time, it ensures proper performance in the system environment, and it reduces cost and space. However, many first-generation products will use analog building blocks until system chips become available. In addition, there are many products that don't have the volume to justify a dedicated system chip.

But even those products that won't have single-chip solutions will benefit from analog-digital integration. Mixed-signal subsystem chips, which combine several analog and digital functions but don't integrate the entire system, will provide low-cost, high-performance alternatives to multi-chip designs in a variety of systems. An example is the mixed-signal IC shown in the figure. This subsystem chip combines a temperature sensor, an analog-to-digital converter with seven external voltage inputs, two fan speed counters, numerous registers, and an I2C interface. This one chip replaces several ICs with a single system monitor chip. This sort of "system health monitor chip" helps protect many types of products from excessive temperature, fan failure, and other problems, and thus serves as a protection subsystem. Other mixed-signal subsystem ICs perform such functions as sensor signal conditioning in document scanners and digital cameras, dramatically reducing parts count and improving performance.

Q.: But isn't there a performance gap? Can a system-on-a-chip ever have the performance of separate analog building blocks built on dedicated analog processes? Will poor analog performance prevent the system-on-a-chip from meeting the needs of target systems?

A.: A performance gap often exists, but it will usually favor the system-on-a-chip. Even when a separate analog block is necessary, overall performance is almost always better when it is used with a system chip rather than other general-purpose analog components. System chips are simply better tuned to the needs of the target systems. Interface issues among, and between, analog and digital blocks generally disappear. And analog performance on system chips is enhanced by the availability of digital calibration and error-correction techniques.

Q.: How will the system-on-a-chip change analog?

A.: It will increase the demand for the best mixed-signal engineers. Because mixed-signal system chips require uncommon skills to define, design, test, and manufacture, they will dramatically increase the demand for the most talented mixed-signal engineers.

It will also change the way analog is designed. Designers are learning new techniques for squeezing the highest possible analog performance from low-voltage, mixed-signal CMOS processes that are optimized for very high-volumes. They are also learning how to make those analog functions coexist with noisy digital circuitry on the same chip. And they're learning to make those designs production-worthy faster than ever before. And it will increase the size of the analog market. By reducing cost and development times, the system-on-a-chip will put more analog in the hands of more consumers than ever before. It will increase the total volume of analog circuitry on chips and in systems. In doing so, it will cause a shift in the analog center-of-gravity from standard building blocks built on specialized processes toward specialized analog subsystems built on high-volume mixed-signal processes.

Q.: But won't this be a disaster for manufacturers of standard analog components?

A.: No. Because much of the growth in mixed-signal system chips will be in products that didn't exist before, the growth in system-chip analog will have little or no negative effect on the sales growth of standard analog ICs. For the analog market as a whole, the system-on-a-chip will drive a bigger, better business.