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Analog Devices Announces 14-Bit, Low-Power A/D Converter in Chip-Scale Packaging

Industry's first 3 V, 14-bit, 80 Msamples/s A/D converter with sub-500 mW power consumption for wireless infrastructure applications.

The manufacturer says . . .

ChipCenter's Paul O'Shea says . . .

Analog Devices Inc., a provider of high-performance semiconductors for signal-processing applications and the market-share leader in data converters, introduced the industry's first 3 V, 14-bit, 80 Msamples/s A/D converter with breakthrough sub-500 mW power consumption. This low-power A/D converter augments ADI's family of high-speed A/D converters available in chip-scale packages (CSP), including pin-compatible 10- and 12-bit versions that were announced in September, 2002. ADI's CSPs deliver the same levels of performance in packages that are 87% smaller than previously offered packages. "Wireless-infrastructure manufacturers and carriers are looking to ease design challenges and cut cost as they drive the adoption of next-generation wireless standards," said Kevin Kattmann, product line director for High-Speed Converters, Analog Devices. "The low power and small size of our ADCs in chip-scale packaging allow wireless engineers to design more cost-effective radios while maintaining current levels of performance." The new chip, the AD9245, is suitable for pico-cell and micro-cell designs with multiple base stations on one tower, or locations where low power consumption is advantageous, such as distributed base stations for "hot spots" or in buildings where a medium network capacity is needed. It also enables migration from single-carrier to multi-carrier platforms, allowing designers to keep costs down while maintaining 14-bit performance. The AD9245 uses a multistage differential pipelined architecture with output-error-correction logic to provide 14-bit accuracy at 80 Msamples/s data rates, and guarantees no missing codes over the full operating temperature range. It operates with a signal-to-noise ratio of 72 dB and a spurious-free dynamic range (SFDR) of 85 dBc. It is pin-compatible with the AD9235 12-bit, 20/40/65 Msamples/s A/D converter, AD9236 12-bit, 80 Msamples/s A/D converter, and AD9215 10-bit, 65/80/105 Msamples/s A/D converter. The sample-and-hold amplifier features a proprietary input-sampling network that can be configured for single-ended or differential operation, thus eliminating the expense of a single-ended-to-differential conversion stage in a single-ended system. Other significant benefits include: High-performance—A clock duty-cycle stabilizer allows the AD9245 to maintain performance over a wide range of clock pulse widths. This is important in portable applications where the clock source may be less than ideal. Advanced pin-compatibility—Fully compatible with ADI's entire family of 32-pin LF-CSP packaged A/D converters, the AD9245 gives designers a simple upward migration path, allowing a single analog front-end signal chain to be used in various products, with performance that can be differentiated based on the A/D converter chosen. Increased IF sampling capability—The AD9245 supports input frequencies as high as 100 MHz, helping to eliminate a down-conversion stage and reduce the number of components needed to complete the design. In addition, components such as mixers and filters become unnecessary, ultimately lowering the total system cost. Multi-channel application advantages—Power-sensitive multi-channel applications such as ultrasound and high-end medical imaging also benefit from the AD9245's sub-500 mW power consumption. Analog Devices is a leading manufacturer of precision high-performance integrated circuits used in analog and digital signal-processing applications. The company is headquartered in Norwood, Massachusetts, and employs approximately 8600 people worldwide. It has manufacturing facilities in Massachusetts, California, North Carolina, Ireland, the Philippines, Taiwan, and the United Kingdom. Analog Devices' stock is listed on the New York Stock Exchange, and the company is included in the S&P 500 Index. Analog Devices, Inc. Ray Stata Technology Center 804 Woburn Street Wilmington, MA 01887 Tel: 800-ANALOGD (262-5643) Web: www.analog.com

Let's start with a little background for this A/D converter. The AD9245 is the newest member in a family of A/D converters. It has older siblings that offer 10-bit resolution at 65 MSamples/s and 12 bits at 80 MSamples/s. Customers can design a whole system based on this family of A/D converters, depending on the differentiation they want. For example, if they want a high-sensitivity radio receiver, they would choose the new 14-bit 9245 A/D converter, but on the lower end system design they could choose the 10-bit chip. The 9245 is a second-generation 14-bit, 80 Msamples/s A/D converter chip, and its claim to fame is its sub 500-mW power consumption, at 3 V, in a 3210 chip-scale package. The 9245 offers more precision, less power consumption, and faster sampling than previous family members, and you might wonder how ADI accomplished that. Certainly experience is a major point, and migrating to a different process technology is another. This new A/D converter uses the 0.35 µm CMOS process, which allows ADI to squeeze out more power. The net effect of riding the shrinking process is the decreased power consumption. But this means continual reinvestment in the technology—and that isn't free. So why does ADI do this? Simple—to remain the dominant player, and because power consumption is an important spec for today's designs. Oh, and did I mention that ADI thinks this low-power 500 mW chip will enable other applications that other higher power consumption chips prevented? The company thinks it will enable four markets (that need low power in pico and micro cells), including wireless infrastructure. For example, the service providers for pico and micro cells typically need to increase capacity and extend the range in a building. Low power is needed because the cells are small boxes that typically can't be in an air-conditioned space that would keep the components cool. The other markets (that need a smaller footprint and higher sample rates) ADI is looking at are broadband wireless and medical imaging (including ultrasound, PET scan, CAT scan, and MRI, which need multiple channels and low power), and for handheld test equipment (that needs to be portable and be able to work with low power). Under the category of experience is the use of creative tricks that ADI used for the pipeline converters. The company continues to optimize these pipelines so that power is conserved or optimized. In the past, a designer's first inclination was to throw power at the design to meet the specs. Now designers are trying to meet the specs with half the power, and the results are seen in the 9245. Maybe this is why it's no secret that ADI is the leader in A/D converters, with 33% of the market in 2002 according to Databeans Research. The company continues to push into the high-speed converter market with this 14-bit A/D converter, and now offers it in chip-scale packaging that reduces the previous chip size by 87%. ADI supports both single-ended and differential applications, and the design engineers work on optimizing and to achieve the performance you need for a truly differential input because everything is balanced in the sampling. At the same time ADI recognizes that some applications require single-ended inputs, and we need to convert that input into a differential input inside the chip to have the required performance. So it's converted to a differential input on-chip, and the pipeline is based on the differential sampling network. The integration is targeted at the cost-sensitive markets and what ADI can do for them. In general, ADI focused on a wide range of applications and making them easy to use. Ten years ago the state-of-the-art 12-bit 40 Msamples/s A/D converter was actually an MCM, which was the size of a small brick and took a car battery to power up (okay, maybe not that much power, but you get the idea). A lot has changed in that time, but there are still the same user problems such as clock jitter, noise suppression at board level, and coupling of noise back into the A/D converter. ADI has focused on those problems, and offers features such as a clock duty cycle stabilizer that simplifies or loosens the constraints that the system engineer has to worry about for the clock. The clock duty stabilizer is a neat thing because it only looks at the rising edge of the clock input and creates a 50% duty cycle internally to create the falling edge. Much is being done on both edges of the clock, not just the rising edge, within the A/D converter. For example, that stabilizer circuit was introduced with the 9226. There are other techniques used in the 9245, including matching elements within the A/D converter so the spurious-free dynamic-range performance is optimized using something called shuffling elements. That means, for example, if you run the 9245 at lower sampling rates, you will achieve lower power consumption. So there is a scaling effect in terms of dynamic power consumption. Finally, the old architecture for base stations used to be one signal chain per carrier. So you would have the entire signal chain, including the A/D converter and a digital chip per carrier, and if the base-station manufacturer had another carrier in that area, it would have to duplicate the entire signal chain. Migrating to a 14-bit A/D converter chip enabled the base-station manufacturers to reduce the duplication to just the A/D converter. It reduces the number of A/D converters in a base station, but the resolution needed goes up and simplifies the architecture of the base station. The AD9245 is packaged in a 32-pin CSP, and is priced at $38.00 per unit in 1,000-piece quantities. Samples and evaluation boards are available now. Full production is scheduled for April ,2003. Datasheet

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