With customers' engineering ranks thinned by a sluggish economy, makers of high-performance analog-to-digital (A/D) converters are seeking to gain new business by adopting strategies that focus on customization. Competition now revolves around the value a vendor can add to an application, and not simply the raw processing speed or resolution of a "vanilla" device.
"Having the best speed or resolution is not always valuable, especially for high-volume applications. It's more important to understand the customer and the application, and to tailor a design to meet performance and cost parameters," noted Julian Hayes, marketing director at Wolfson Microelectronics Ltd. (Edinburgh, U.K.).
"The challenge among converter manufacturers is to make A/Ds as application-specific as possible without pigeonholing their devices into a one-time buy," said Mike Britchfield, product-line director of precision converters at Analog Devices Inc. (Norwood, Mass.). "We've come to follow a business case approach to providing solutions. Because many high-performance converters tend to be narrowly focused from an application or market perspective, the amount of engineering talent that we devote to developing a 'niche' product is something we seriously consider."
Britchfield cited as one example the trend toward integration of post-processing and analog front-end (AFE) signal-conditioning elements into A/D converters. Analog Devices' AD7725, based on a sigma-delta architecture, features software-selectable roll-off filtering and digital post-processing. The company is also addressing the need to integrate front-end (preconversion) signal conditioning. And, Britchfield added, "in addition to integrating voltage references or programmable gain amplifiers, which are commonplace today, we're building converters with on-board instrumentation amplifiers." The 12-bit, 16-channel, 1-Msample/second AD7490, with on-board sequencers, is another example of digital integration. The sequencers are used to select the order in which channels acquire signals.
Also employing an integration strategy is Datel Inc. (Mansfield, Mass.), which focuses on high-resolution (14-, 16- and 18-bit) converters operating at 1 Msample/s or more. The company has integrated correlated double-sampling front ends, according to marketing manager Bob Leonard, and is readying a dual 14-bit converter.
Another customization strategy, adopted by companies like Texas Instruments Inc. (Dallas), is to offer converter, operational amplifier and/or digital signal processor combinations that are designed to meet particular market requirements. Last summer, TI introduced the 10-bit, 40-Msample/s ADS5203 and ADS5204 A/Ds, each offering a 60-dB signal-to-noise ratio (SNR), for baseband communications, video processing, medical imaging and portable-instrumentation applications. An on-board programmable gain amplifier allows users to adjust the gain of each set of inputs in order to match the amplitude of an incoming signal. "When combined with our high-speed driver op amps, these converters allow TI to offer a complete solution for baseband, video and imaging applications," said Ed Fullman, marketing manager for TI's high-speed data converter products.
Emerging market demands are prompting converter makers to focus on particular figures of merit, among the most important of which are SNR and spurious-free dynamic range. "Both are important due to the performance demands of multicarrier 3G third-generation cellular basestations," said Maher S. Matta, business manager for the high speed data converter product line at Maxim Integrated Products (Sunnyvale, Calif.). "Also, tremendous cost pressures are driving the need for data converters that are able to capture and transmit high IF intermediate-frequency signals. Cost reduction comes from elimination of the components needed for one or two intermediate IFs."
Matta said that Maxim is working on several products that address that need, including the forthcoming 15-bit, 100-Msample/s MAX1430, which is expected to offer "best-in-class" dynamic performance.
National Semiconductor Corp. (Santa Clara, Calif.) is also addressing basestation requirements for high speed, high resolution and high bandwidth, according to Suresh Ram, product manager for high-speed converters. "We're currently offering 12-bit converters for those applications but are working on 14- and 16-bit parts with sample rates of 65 to 80 Msamples/s and higher," he said. "At the same time that customers want higher speed and bandwidth, they also want a higher level of integration and lower cost. We currently offer a dual 12-bit, 40-Msample/s A/D and are working on dual devices at higher speeds."
A balancing game
In order to satisfy customer demands, companies must go through the complex process of mastering multiple architectures. "The A/D converter equation balances speed and resolution within pipeline, successive-approximation-register and delta-sigma architectures, and we have to push the envelope within each one," said Todd Nelson, marketing manager for converters at Linear Technology Corp. (Milpitas, Calif.). His company is developing a new family of 16-bit converters.
Analog Devices Inc.
Linear Technology Corp.
Maxim Integrated Products
National Semiconductor Corp.
Texas Instruments Inc.
(800) 477-8924, ext. 4500
Wolfson Microelectronics Ltd.