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ADI revs up high-speed data conversion

Posted: 02 Jul 2008 ?? ?Print Version ?Bookmark and Share

Keywords:high-speed data conversion? 16bit SAR ADCs? data converter?

The sleepy data converter sector is suddenly heating up, as Analog Devices Inc. has leapfrogged the competition to help enable a new class of industrial, medical and related equipment in the marketplace.

ADI, the world's largest data converter supplier!has rolled out what it claims are the industry's fastest 16bit successive-approximation register (SAR) ADCs. The two new members of ADI's PulSAR family of precision 16bit SAR ADCs are targeted for a new generation of digital X-ray systems, magnetic resonance imaging (MRI) equipment, computer tomography and related gear. The AD7625 operates at 6MSps, while the top-of-the-line AD7626 runs at 10MSps. The PulSAR family is based on CMOS technology and an ADC architecture that has a zero data-latency rate, which is critical in precision data-acquisition systems, according to ADI.

Previously, ADI's fastest 16bit SAR ADC operated at 3MSps. With the new products, ADI reportedly has regained the 16bit SAR ADC speed record from rival Texas Instruments Inc. Last year, TI rolled out a 16bit SAR line said to operate at 4MSps.

'Analog' Moore's Law
Data converters, which include ADCs and DACs, are critical signal blocks that connect the separate analog and digital worlds. In one of the more specialized data converter categories, SAR-type products are fast, general-purpose devices said to have little or no pipeline delay.

A general rule of thumb is that converters running in excess of 40 or 50MSps are high-speed devices, while those operating at lower speeds are focused on "precision" applications. In this case, the AD7626 is the fastest 16bit converter in its class (SAR), and the end applications are focused on "precision-like products" such as digital X-ray equipment.

Industrial applications remain the biggest market for data converters. Within that space, the booming medical field is pushing suppliers of data converters to new limits, said Dick Meaney, VP of precision signal processing at ADI.

Meaney described the phenomena as the analog version of Moore's Law. In digital, the amount of transistors in a chip is supposedly doubling every 18 months, although there are signs that the cycle is slowing. There is also a shift toward new processes every two years.

In analog, device density isn't doubling every cycle, and the process migrations tend to move at a snail's pace. But as in the digital sector, analog vendors are under pressure to "fit more and more in the same space" with lower power consumption and at cheaper prices, Meaney said. And unlike most digital markets, the data converter market "remains a steady business," said Susie Inouye, research director, president and CEO of Databeans Inc. In total, the data converter market is projected to jump 18 percent in 2008, but it will slow and grow by 12 percent in 2009, she said. That's still a better outlook than the semiconductor market, which is projected to see single-digit growth in 2008. On the downside, there are some falling ASPs for data converters, especially for low-margin temperature sensor products, she said.

In 2007, ADI had a 47 percent share of the overall data converter market, followed by TI (19 percent) and Maxim (10 percent). Other suppliers include Linear, National, Fairchild, Intersil and ST.

ADI's Meaney is slightly "more cautious" about the data converter market, saying growth could be closer to 10 percent this year. In its most recent quarter, ADI's data converter business was up 6 percent sequentially, which exceeded expectations, said Doug Freedman, an analyst with American Technology Research Inc. Data converters represent 46 percent of ADI's total sales.

While ADI is expanding its core analog, data converter, DSP and related markets, it is bailing out of others. In the past year, Taiwan's Mediatek Inc. acquired ADI's baseband chip products and On Semiconductor Corp. acquired ADI's voltage regulation and thermal monitoring lines.

Market opportunities
Meanwhile, to keep its lead in one segment, ADI is chasing after a slew of different data converter markets. The SAR-based market is especially appealing, as the ASPs are holding steady and "pretty close to the list price," Inouye said.

One high-margin market appears to be medical, especially computer tomography (CT). X-ray CT!including conventional, helical and electron-beam forms!provides cross-sectional images of the chest, heart and vessels, according to the American Heart Association. Today's advanced CT systems from GE, Toshiba, Philips and others are so-called 64-slice machines. For example, Toshiba Corp.-s Aquilion 64 is based on the company's 64-row Quantum detector technology. The Quantum detector enables the Aquilion CT scanner to acquire 64 simultaneous slices!or views of 0.5mm with each 350ms gantry revolution, allowing isotropic imaging of any region of the body during a single breath-hold,!according to Toshiba. In March, Toshiba rolled out the world's most advanced CT system. The so-called Aquilion One is said to be a 320-slice machine. The Aquilion One can give physicians all the information they need to diagnose and treat a patient in less than 20mins and with a significantly lower contrast and radiation dose, Toshiba said.

It's unclear if ADI is supplying the data converter to Toshiba, but the SAR-based products are playing a key role in enabling new medical gear. ADI is also targeting these devices for traditional applications, such as automatic test equipment and other products. Based on 0.25?m CMOS technology, ADI's AD7626 PulSAR ADC achieves a new level of 16bit data-capture performance, with 15bit ENOB (effective number of bits) and 10MSps throughput. The ADC has a 92dB SNR, which is 8dB (1.3bits) better than any ADC in the market, according to ADI.

For applications that don't require a full 10MSps data rate, the AD7626 can be multiplexed. ADI is offering the AD7626 in a two-channel configuration, where each channel operates at 5MSps. This would allow OEMS to lower materials costs by reducing data converter component count by 50 percent.

The AD7626 consumes 130mW of power. The AD7626 also uses a self-clocked low-voltage differential serial bus, which reduces the number of external components required to address board-level noise concerns. ADI also rolled out the AD7625 16bit PulSAR ADC, which operates at 6MSps. The AD7626 and AD7625 ADCs come in 32-lead QFN packages and are priced at $34 and $32 per unit, respectively, in 1,000-unit quantities.

In addition, ADI new sigma-delta ADC features the industry's best combination of data rate and noise-free resolution. ADI's 24bit AD7190 sigma-delta ADC achieves greater than true 16bit noise-free resolution of up to 2.4kHz across all input voltages from 40mV to 5V.

- Mark LaPedus
EE Times





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