ADI's data converter business reflects a mixture of standbys and custom brews

It's not so much that balance between standard linear building blocks and ASSPs (application-specific standard parts) has changed, said Dick Meaney, vice president of the company's precision data converters group. The business mixture of standard-and-semi-custom has been a consistent 60 percent to 40 percent since the mid-1990s, he said. Rather, the applications for ASSPs have themselves shifted, and are now demanding entirely different specifications, technologies and engineering tradeoffs.

Where engineers were once balancing resolution and conversion speed (along with power consumption and cost), Meaney said, they are now honing in on concepts like spurious-free dynamic range (SFDR), and only paying for the effective number of bits (ENOB) they need for their particular application - even if that number turns out to be something like 9 1/2.

New applications like Ultrasound Scanning, for example, demand high SNR and ENOB for high-image quality, but also something rarely specified before — over-range recovery — explained Kevin Kattmann, the product line director for high-speed converters (traveling with Meaney). Ultrasound imagers are effectively radar processors, using a phased-array antenna to bounce high frequency signals (256 of them) off of an object, and then creating an image based on the time it takes for each of these signals to bounce back to a sensor array at the antenna. Soft tissue will partially absorb and attenuate the signal and take a longer moment to return it; hard tissue, like bone, will show a much stronger reflected signal.

"The problem occurs when the scanner hits soft tissue right after encountering a solid object," Kattmann explained. "The front end gain amplifier must quickly reset, to crab the next set of samples. Otherwise, you'll have a blurred image." The front end of these converters need as much as 50 percent over-voltage range protection, with the ability to bounce right back to the proper input range, Kattmann said.

This is attention to the fine details of data converter applications is nothing new to Analog Devices, which holds a 45 percent share of $2.4 billion 2004 market according to recent assessments by Gartner Dataquest. Maxim Integrated Products (Sunnyvale, Calif.) is number two in this market, with a 15 percent share; Texas Instruments (Dallas) is number three with a 14 percent share. National Semiconductor Corp, (Santa Clara) and Linear Technology Corp. (Milpitas) continue to jockey for fourth and fifth positions.

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Other examples of the specialized markets ADI now serves with data converters include cellular basestations, set top boxes, digital still cameras and high resolution television systems. Cellular basestations require high SFDR (up to 16 bits), to capture weak phone signals in the presence of strong ones, and an extremely high sampling rate (100 Msamples/s) to simplify the job of down conversion performed by receivers.

Set top box (STB) makers are now asking for 12-bit resolution where they were once content with 8 bits — though the human eye will barely sense the difference in pixel light intensity between 6 and 7 bits, Kattmann said. But a 12-bit resolution helps STB makers interpolate legacy video material onto newer high-resolution screens.

AC linearity — low noise, for example — serves CCD image processing in digital still cameras and camera phones. In addition, manufacturers want a high degree of integration to accommodate miniaturization and low power consumption to support longer battery life, ADI said.

In these applications, multiple-chip packaging techniques like stacked die help camera phone makers get data converters, image processors, zoom and autofocus drivers all into one IC package, said Dick Meaney.

As a rule, ADI does not trade its highly-valued converter IP to SoC designers, Meaney insisted. But the company is not averse to building its own integrated SoCs or multi-chip modules for selected customers, he said. #