Wednesday, March 30, 2005

This week's new product releases

ADuM2400: Quad-Channel Digital Isolator, 5.0 kV (4/0 Channel Directionality)
ADuM2401: Quad-Channel Digital Isolator, 5.0 kV (3/1 Channel Directionality)

Sunday, March 20, 2005

This week's new product releases

AD5258: Nonvolatile, I2C-compatible 64-position, Digital Potentiometer
AD7656: 250 ksps, 6-channel, simultaneous-sampling bipolar 16-bit A/D Converter
AD7942: 250 ksps PulSAR 14-bit A/D Converter in SO/QFN

Tuesday, March 08, 2005

This week's new product releases

ADP1611: 20 V,1.2 MHz Step-Up DC-to-DC Switching Converter
AD5259: Nonvolatile, I2C Compatible 256-Position, Digital Potentiometer

Wednesday, March 02, 2005

A Smart Modem for Robust Wireless Data Transmission Over ISM Bands

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Enhance Processor Performance in Open-Source Applications

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Blackfin Processor’s Parallel Peripheral Interface Simplifies LCD Connection in Portable Multimedia Applications

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Editor's Notes—Volume 38, Number 4, 2004

You’ve opened the book on the final quarterly issue of 2004, our 38th sequential year in print—and 6th on-line, at Perhaps you’ve read all four issues cover-to-cover. Or perhaps this is your first acquaintance with Analog Dialogue. In any event, here’s your opportunity to spend a moment to be tempted to read an article you may have missed—or to contemplate a title that you’ve already read. You can find copies of all these issues on-line in the archives:

The year started—in Number 1—with PID control algorithms, fan-speed in temperature control, and video technology in automotive safety. In this column, you could have read a rambling historical discourse on (mostly—but not entirely—analog) multipliers.

In the following issue—Number 2—you (could have) read about current measurement in solenoids for automotive controls, bridge amplification with digitally programmed gain and offset, and practical techniques to avoid op-amp instability due to capacitive loading. There was also a description of techniques we use for in-package trimming of a low-cost CMOS amplifier with wide bandwidth, offsets less than 65 µV and drifts less than 7 µV/ºC.

The penultimate issue, Number 3, had an “Ask The Applications Engineer” (#33) feature on direct digital synthesis (DDS), plus articles on JPEG2000 image compression and a digitally adjustable cable equalizer. You also could have read about a reader’s discovery—in a NASA vehicle, in equipment designed before he was born—of an ingenious but deceptively simple hot-wire anemometer. Its design principle was described in a (still interesting) article on measuring fluid flow with a self-balancing bridge; originally appearing in our Volume 5, in 1971, it was reprinted in this issue.

And in these pages today you can read about our designer-oriented updated web site, a new software tool for memory-efficient real-time audio designs, and an “Ask The Applications Engineer” (#34) on wideband CMOS switches.

Thus we close the book on Volume 38 and look forward eagerly to Volume 39, which will commemorate Analog Devices’s 40th year of providing the electronic industry with innovative products, guidance, and ideas for analog- and digital real-world signal processing solutions.

Dan Sheingold []

Satellite Radio, MP3s, and Streaming Audio
Back in the days of analog LPs on vinyl, I owned over 500 record albums. Then, as an early adopter of compact discs, I bought all of my new music on CDs, and even started to replace some of my records. Soon I abandoned the turntable altogether and gave all of my albums to my brother. Sadly, a flood ruined all the records, but I shed nary a tear, exulting in the luxury of the newer, smaller, virtually indestructible CDs.

Yet lately I’ve realized that I rarely buy CDs anymore—and when I listen to them it’s almost always in the car. In my family room I usually listen to one of the dozens of commercial-free, CD-quality audio channels that are available over the digital cable. It makes available a much wider variety of music, and lets me view trivia, history, and other information on the song, album, and artist. When at the computer, I listen to streaming audio from one of several providers, using one of the available media players. The small annual payment for this service makes it possible to listen to high-quality audio from over 1000 stations and lets me download my favorite songs for a nominal additional fee.

At the gym, at the beach, or in the backyard, I listen to my MP3 player. Where do the MP3s come from? Most were ripped from my CD collection, but the newest ones are all downloads. Why buy the whole CD when I need buy only my favorite songs—for a fraction of the cost—and eliminate the storage problem at the same time.

In the car, I listen mostly to the radio, but am constantly annoyed and frustrated by the large number of commercials, especially at drive time. Although I listen to CDs in the car, those jewel boxes take up too much space and are too hard to open safely while driving. CDs in sleeves are more space efficient and are easier to handle, but they’re sometimes hard to identify without their covers. An FM modulator lets me listen to my MP3 player in the car, but the audio quality is not as good as a CD, and it’s sometimes difficult to find an unused radio frequency in Boston’s busy metropolitan market.

Thus, one option that now tops the priority list for my new car is satellite radio, either XM or Sirius. In the early days of cable, skeptics wondered why people would pay to watch TV when they could watch it for free. Today, many people feel the same way about radio, but I look forward to the day when I can give my CD collection to my brother and rely on streaming media wherever I go.
Why am I writing about this here? Because as I drive to work each day I can feel proud that Analog Devices offers amplifiers, converters, and processors that enable satellite receivers, set-top boxes, computer audio, and MP3 players to be small, flexible, power-efficient, and inexpensive—all the while providing high quality and functionality—plus the software that helps developers to quickly bring these products to market.
Your comments are welcome.

Scott Wayne []

Editor's Notes—Volume 38, Number 3, 2004

It’s interesting to observe that the three feature articles in this issue are highly representative of the currents that are basic to our businesses. Each illustrates a facet of what real-world signal processing (and Analog Devices) is all about—digital, analog, and the interface. They exemplify our long-held conviction that, although we live in an analog physical world, analog and digital must cooperate to solve each other’s problems.

Take, for example, JPEG 2000 Image Compression (page 3). The JPEG 2000 standard defines a new image-coding scheme that uses state-of-the-art compression techniques based on wavelet technology. Its architecture is useful for many applications, including Internet image distribution, security systems, digital photography, and medical imaging. The article highlights some of its benefits.

The technology involves applying the highly sophisticated wavelet transformation in a purely digital interpretation scheme for encoding, transmitting, receiving, storing, and selectively using pictorial material, Yet it starts with electrical samples that depend on light intensity (an analog quantity), and is intended for ultimate display in some form by modifications of light from a source to produce pixels of light whose intensity (an analog quantity) correspond more-or-less faithfully to an intended relationship to the original.

Consider now, if you will, Adjustable Cable Equalizer Combines Wideband Differential Receiver with Analog Switches (page 13). Category-5 unshielded twisted-pair cable, like any transmission medium, suffers from dispersion and high-frequency signal loss. This article presents an equalizer design that compensates Cat-5 cable at frequencies to 100 MHz and lengths to 1000 feet, making it suitable for KVM networking and high-resolution video transmission.

The subject of this article is, quite evidently, preserving the integrity of analog signals. But what do the initials, KVM, stand for? Keyboard, video, mouse! What could be more digital? Again, we have a scheme for preserving information, but this time the purpose of the design is to preserve digital information—subjected to the tender mercies of the analog world in the cable. Since KVM suggests computer, the source and destination of the information could both be totally digital in nature—starting with symbols and ending with symbols.

Finally, we have: All About Direct Digital Synthesis—Ask the Applications Engineer–33 (page 8). Direct digital synthesis (DDS) is a method of producing an analog waveform—usually a sine wave—by generating a time-varying signal in digital form and then performing a digital-to-analog conversion. Because operations within DDS devices are primarily digital, they can offer fast switching between output frequencies, fine frequency resolution, and operation over a broad spectrum of frequencies.

The operation speaks for itself! The properties of the waveform to be generated enter in purely symbolic form as numerical information (btw, the French word for “digital” is numérique). And lo! the device’s DAC—in cahoots with the clock that (along with the power supply) is essential to the device’s operation,—emits an analog waveform of the appropriate frequency and phase.

Dan Sheingold []

Analog gets a bad rap, even in popular culture. In movies, TV shows, and magazines, people are told that analog is dirty and old fashioned, and that digital is clean and modern. In an ad from one of the electronics superstores, for example, a guy gets dumped for being “too analog”. In The Teeth of the Tiger by Tom Clancy[i], readers are told that

The world was not digital, after all—it was an analog reality, always untidy, always with loose ends that could never be tied up neatly like shoelaces, and so it was possible to trip and fall with every incautious step. (page 172);
The world, one had to remember, was analog, not digital, in the way it operated. And analog actually meant sloppy. (page 286);
“I think that we can depend on that.” “Yeah, unless he got an unexpected phone call, or he saw something in the morning paper that caught his interest, or his favorite shirt wasn’t properly pressed. Reality is analog, Sam, not digital, remember?” (page 316).

Clancy is right—the world is analog. But that doesn’t make it dirty, unpredictable, or imprecise. While digital signals are limited by finite resolution, analog signals can have infinite resolution, limited only by noise or quantum effects. Analog signal processing can respond nearly instantaneously, without the computational delays inherent to digital signal processing. Analog circuitry can often operate at far lower power levels than digital circuitry providing the same function. Yet it is difficult to maintain the speedy, pristine nature of an analog signal through further signal processing for communications or storage, especially over long distances, in hostile environments, or over extended periods of time. Thus, the world needs precision data converters, high-speed operational amplifiers, power management components—and the expertise to use them.

The images in a digital camera are stored as 1s and 0s, but they are acquired by a CCD analog imager. Processing the CCD signal requires analog functions such as sampling, variable-gain amplification, and A/D conversion. Displaying the image on the liquid-crystal display requires analog functions, such as D/A conversion, filtering, and gamma correction. Many digital cameras include audio functions, and therefore require audio codecs and amplifiers to drive the speakers and microphones.

Wireless communication is also made possible by analog technology. Cellular carriers brag about their all-digital networks, but humans don’t speak in 1s and 0s, and don’t hear that way either. Voices must be digitized by A/D converters and reconstructed by D/A converters. And, while the data being transmitted is digital, the transmission medium is analog. 1s and 0s can’t be transmitted as-is—they must first be modulated onto high-frequency carriers. On the receive side, weak signals must be captured by low-noise amplifiers—and demodulated. Power for all of these functions must be supplied by a small battery that lasts for weeks between charges, can be recharged quickly, and can be used while it is being charged. This requires complex analog power-management techniques.

Analog Devices, with its technologies, products, application notes, data sheets, application seminars, design tools, web site, field application engineers—and publications such as Analog Dialogue—seeks to help foster both the technology and expertise that designers—trained in either analog or digital—can use to cope with the realities of a mixed-signal world.

Scott Wayne []

[i] Tom Clancy, The Teeth of the Tiger. New York: G. P. Putnam’s Sons, hardcover (2003).

Editor's Notes—Volume 38, Number 2, 2004

These words are being written in the second half of the thirty-eighth year of Analog Dialogue’s existence in print (Volume 38). That number, 38, is a relatively undistinguished number: it’s not a prime number—and even expressed as the product of two primes, 2×19, it is still not particularly interesting. One could perhaps stir up a little interest by noting that it’s also 2×(20–1) or 2×(2×2×5‑1)—or 2×(22(22+1)–1. But somehow, round numbers seem more interesting historically. Take, for example, 35 (=52)+5×2)), which is the number of years of service the undersigned will soon complete as the editor of this publication. For such occasions, in the same way as for alumni reunions, we celebrate only multiples of 5 years, while the in-between years, though equally long, go unrecognized (yet they inexorably accumulate the passage of time).

Much more interesting numerically, our editorial colleague, Scott Wayne, also celebrating a quintennium, has been at Analog Devices for a quarter century, 25 (=102/22) years. His personal reflections about that passage appear below.

In 1969 (Volume 3), the fourth year of existence for Analog Devices, our product catalog overwhelmingly comprised high-performance modular discretely assembled operational amplifiers; later augmented by our first data-converter family—inherited in our acquisition of Pastoriza Electronics, Inc. during that year. Five years later (Volume 8, 1974), solidly entrenched in the semiconductor op amp and analog-circuits business—and having become the world’s recognized leader in data converters—we introduced the AD7520, the first monolithic CMOS 10-bit DAC.

In 1979 (Volume 13), we acquired Computer Labs, in Greensboro, NC—extending our converter leadership into the high-speed market. (That year we also introduced a “box”—the ill-fated MACSYM integrated measurement-and-control system—which even had its own language—but within a few years, it had the misfortune to find itself in competition with products using the PC!). By 1984 (Volume 18), we had already introduced our first DSP ICs and were rapidly consolidating our lead in conversion ICs.

1989 (Volume 23) was the year in which we attained the across-the-board high ground in high speed, featuring the fast-slewing-and-settling AD843 and AD844 op amps, the 120-MHz AD640 log amp, 300-MSPS AD9028 8-bit flash ADC, and the 500-MHz AD834 analog multiplier. In 1993 (Volume 28), our highly successful SHARC®, entered the floating-point DSP fray, and ADI pushed the door open wider in high-speed RF analog with devices such as the 500-MHz AD831 mixer.
And just five years ago (1999, Volume 33), the communications world was revolutionized by the Othello direct-conversion radio chip set. Also in that year, we initiated joint publication of Analog Dialogue, on-line and in print, achieving at last the benefits of timely publication, and direct contact with our readers, while retaining the relative permanence of print.

Dan Sheingold

Dan Sheingold and I recently celebrated our respective 35th and 25th anniversaries at Analog Devices. At our service award dinner we learned that there were approximately 200 Massachusetts-based ADI employees who were also celebrating 15-, 20-, 25-, 30-, or 35-year anniversaries in 2004. This got me to thinking: If this were a typical year, at least 1,000 employees, or about 1/3 of ADI’s Massachusetts work force, would have more than 10 years’ tenure. How did this compare to other companies?

Consulting the US Department of Labor website, I was surprised to learn that this was not unusual. While the median length of time that employees have been with their current employer is only 3.7 years, fully 31% of workers have 10 or more years under their belt.

So, what makes an employee and a company want continue their association for such as long time? For me, it was a combination of such things as great co-workers, opportunities to do new things, constant challenges, continuous learning, and solid corporate management.

Trained as an electrical engineer, my first 20 career years were spent in design, starting with high-resolution converters in 2″×2″ modules. As customer demands changed and our technology evolved, I worked on our division’s earliest hybrid and compound-monolithic converter designs, later branching out into signal-conditioning and isolation products. I then transferred to the semiconductor division, working on bipolar and CMOS IC designs.

Five years ago I joined corporate marketing, where I am now doing teaching, editing, and publishing. Rather than feeling trapped in a single job for 25 years, I have progressed through a series of jobs, continually learning new things, encountering new challenges, and enjoying the benefits of closer contact with customers and a view of our products and fellow engineers with an extended horizon.

The biggest factor that many people cite as contributing to their longevity with a company is the people. (It may also be why people leave some companies.) Throughout my career at Analog I have been privileged to work with some of the best, brightest, and nicest people that you could hope to meet—people who seem more like friends or extended family than simply co-workers.
An additional way that companies motivate employees to stick around (and do their best) is by empowering them to make the decisions that they need to get their jobs done on a day-to-day basis with a minimum of oversight or bureaucracy.

There are of course more tangible considerations, such as salary, vacations, and other concrete benefits. They must be competitive with those of other employers. Although long-timers feel that they can get more spiritual satisfaction by staying with a company, yet others feel that they can get more material benefit (or eliminate sources of dissatisfaction) by leaving to join a new company.
We’ll welcome your feedback on what motivates people to stay with companies—or jump around—and to what degree they have that choice. In the newspapers, we seem to read only the horror stories—but perhaps that’s what sells papers!

Scott Wayne []

Editor's Notes—Volume 38, Number 1, 2004

Some 33 years ago, we noted the introduction of the AD530—the world’s first complete analog multiplier-on-a-chip—with a rambling historical discourse appropriately dubbed, “Multiplier Memories and Meanderings.” Eighteen years later, with many successful generations of multipliers—and a growing family of other translinear devices—in our portfolio, you could have read a column entitled, “Multiplier Meanderings—Revisited,” as we feted the arrival of the 500-MHz AD834. Now—and for no overriding reason, other than an implied promise buried in the last issue—we continue to meander and furnish the newer generation of readers with thoughts about multipliers—and related devices—originating farther up the stream of time, as well as to jog the memories of readers whose ripening with time may have paralleled our own.

An analog multiplier is in a special category of nonlinear electronic devices, since it can represent either an externally applied linearly adjustable (modulating) influence or a means of introducing a parabolic (i.e., 2nd-degree) function for analog computation—and can be connected in a feedback loop to perform division.

Although our earliest and ongoing primacy is in analog multiplier design, we should note that, as the world’s “house of multipliers” Analog Devices is no stranger to IC electronic multipliers of digital- and hybrid (“mixed-signal” in today’s lingo) provenance. One of our first DSP products was a fast digital multiplier in CMOS (1983) ; and our very first 10-bit CMOS D/A converter, the AD7520 (1974), was a multiplying DAC.

In the vacuum-tube years, well before silicon and the Gilbert approach, the design of analog multipliers with adequate linearity and bandwidth posed daunting challenges. Servos were accurate, but too slow for repetitive computation (and they had mechanical parts that could wear out). Linear modulator circuits were available, but the gain and biasing required to operate at the standard voltage levels and polarities needed for computing made them impractical for general-purpose applications. The elegant “quarter-square”
* relationship for a while seemed to offer the method of choice, since it offered a direct, symmetrical, mathematical solution—if one could only provide two accurately matched, stable squaring circuits and could accompany them with instantly responding accurate sums, differences, and coefficients at zero drift! This concept, elegant as it was, merely lacked accuracy in practice. As you may surmise, analog multipliers of that era were large and clumsy, hot, expensive, imprecise, and usually of undependable fidelity.

The hottest applications of ICs that involve multiplication (and its logarithmic cousins) are currently in RF, where one finds modulators, demodulators, log amps, mixers, power detectors, rms-to-dc converters, AGC, AFC, VGA, gain- and phase measurement. The strictures of our budget permit little discussion, in this cramped space, of the concepts and applications of multiplication and translinear circuits. The wisest use of the remaining space may be to provide you with pointers to some of the material we’ve published in these pages that you can find either on-line in our Archives
[1], elsewhere in a search of the web site, or in your library:

“Accurate gain/phase measurement at radio frequencies up to 2.5 GHz,” by John Cowles and Barrie Gilbert. Analog Dialogue 35 (2001), pp. 5-8. Archives: find it in Volume 35, 2001.

“Accurate, low-cost, easy-to-use multiplier,” by Barrie Gilbert. Analog Dialogue 11-1 (1977). Archives: Find it in (PDF) The Best of Analog Dialogue, 1967-1991.

“Complete monolithic multifunction chip,” by Lew Counts, Charles Kitcin, and Steve Sherman. Analog Dialogue 19-1 (1985). Archives: Find it in (PDF) The Best of Analog Dialogue, 1967-1991.

“Monolithic IC rms-to-dc converter,” by Lew Counts, Barrie Gilbert, and Dave Kress. Analog Dialogue 11-2 (1977) Archives: Find it in (PDF) ) The Best of Analog Dialogue, 1967-1991.

“Nonlinear circuits handbook,” edited by D. H. Sheingold. Norwood, MA: Analog Devices, Inc., 1976 (out of print).

“Now–True rms-to-dc measurements, from low frequencies to 2.5 GHz.” Analog Dialogue 34 (2000), p. 45. Archives: find it in Volume 34, 2000.

“X-Amp™, a new 45-dB, 500-MHz variable-gain amplifier (VGA) simplifies adaptive receiver designs,” by Eric J. Newman. Analog Dialogue 36, Part 1 (2002), pp. 3-5. Archives: find it in Volume 36, Part 1 (Jan-Jun), 2002.

Dan Sheingold []

We would like to thank the more than 4000 readers who responded to our recent on-line survey. Responses came from 48 states in the US and 66 countries all over the world, with 96% of our readers identifying themselves as designers. We learned that, despite the popularity and timeliness of the Internet: 54% subscribe to the print edition, 43% to the online edition; 61% save their print copies, 21% give it to a colleague. Among online viewers, 57% print online articles, and 12% forward their eNewsletters to a colleague. Most readers told us that they prefer applications articles and tutorials over product articles.

When asked how to improve Analog Dialogue or make it more useful, most respondents said that it was fine as-is, that they wanted more of the same, or that they wanted to subscribe. Some asked for better search capability. As a result, readers can now use Google™ to search the Analog Dialogue website from the Search page or from the navigation bar on most of the main pages. Readers asked for foreign-language versions, and we are happy to announce that Analog Dialogue is now available in Chinese. Readers also asked for a CD-ROM version of Analog Dialogue, so we are considering issuing one as a 40th anniversary bonus, coming up in early 2006.

As always, we value the opinions of our faithful readers, so please send us feedback when you like something that you read, or when you would prefer to see something else instead (or in addition).

Scott Wayne []


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