Monday, November 27, 2006

Ferrite Out Better Core Materials For Your POL Design

Power architectures with nonisolated voltage regulation continue to evolve, and power inductor designs are fundamental to the success of the new product designs. The trend toward two-stage conversion with nonisolated point-of-load (POL) modules is fueling the demand for low-profile, high-power surface-mount inductors with current ratings up to 25 A. Power system design engineers have a wide variety of power inductors at 8 A and higher to choose from when working on a new design. This can be rather overwhelming for a new designer because datasheets can be confusing, and an experienced designer may not be aware of some of the newer core materials available such as powdered iron and ferrite materials. These materials can help reduce size, cost and power losses.

The Right Material for the Right Job

As power densities and current levels continue to increase and more competitors enter the market, product performance becomes critical for successful product sales. For the magnetics design engineer seeking to minimize power losses, the core material selection and physical package size are critical. The job becomes even more difficult as the size of the device decreases and the current increases.

The Right Material for the Right Job

The most common core materials are listed in Table 1. These materials have been around for a long time, but manufacturers are continuously developing new ones. The basic core material ingredient is iron, but it is the alloy blends or oxide formulations and the process controls that give materials their unique performance characteristics. Even though there are many categories, the majority of the materials are considered powdered irons. Categories 1 through 5 in Table 1 outline powdered irons.

Each material category occupies a niche where it is the best material for a given design application. If cost is the critical factor in the design application, then powdered iron is the traditional choice. Table 2 depicts a core material cost comparison using standard powdered iron as the benchmark.

The cost multiplier has been declining in recent years for the ferrite, powdered alloy and high flux materials, because more vendors are developing new materials and selling this type of product. The molypermalloy (MPP) material is cost-restrictive for most applications; however, it is often used for low-volume, height-restrictive applications where a toroidal shape is required. MPP manufacturers are starting to expand their MPP offerings into EIR core shapes, but this product will probably remain too expensive for most high-volume, high-current inductor designs.
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Friday, November 10, 2006

FDA Introduces New Technology to Improve Food Security

The Food and Drug Administration today announced further steps to use modern technology to provide new protections for America’s food supply. First, FDA announced that its new electronic registration system for food facilities, foreign and domestic, will be “live” today at 6 p.m. Eastern Daylight Time. This registration system, available online at and designed to bolster the safety and security of America's food supply, will help with quick identification and notification of food processors and other facilities involved in any deliberate or accidental contamination of food. Second, FDA issued a report to Congress on its progress toward developing more rapid, easier, and less costly tests to detect food contamination.

FDA’s registration system, one of the key provisions of the Public Health Security and Bioterrorism Preparedness and Response Act of 2002 (the Bioterrorism Act), is part of an interim final rule announced by Secretary of Health and Human Services Tommy G. Thompson October 9 and published on October 10 that requires domestic and foreign food facilities to register with the agency by December 12, 2003. As a result, FDA will have for the first time an official roster of foreign and domestic food facilities, allowing timely notification and response in the event of a food safety threat.

“FDA is committed to developing new, more efficient ways to enhance food security, and the new electronic registration system we are inaugurating today reflects that commitment,” said Mark B. McClellan, M.D., Ph.D., Commissioner of Food and Drugs. “Registering online will be fast and simple. Our site will be open 24 hours a day, seven days a week, available to anyone in the world with access to the internet. This new system will permit 400,000 facilities to register worldwide in 60 days, and will give FDA new capabilities to work with everyone involved in our food supply to keep it safe and secure.”

FDA is encouraging electronic registration because it is faster and more efficient than paper registration. Each firm registering online will instantly receive its unique registration number, which will be required for doing business in the U.S. beginning December 12. (Paper registration may be submitted via regular mail or fax.) Facilities will not be charged for registration, which is a one-time procedure.

In addition to the registration rule, FDA last week published a second interim final regulation to enhance the safety and security of the food supply. That rule requires that FDA be provided advance notice of shipments of human and animal food being imported or offered for import into the U.S, also effective as of December 12, 2003.

In arriving at the interim final rule, the FDA worked closely with the Bureau of Customs and Border Protection (CBP) to ensure the new regulations promote a coordinated strategy for border protection. FDA and CBP continue to collaborate intensely on making the new safeguard of prior notice as efficient and effective as possible.

For example, FDA and CBP have worked together so that most notices can come in through the existing CBP system. In addition, FDA and CPB have signed a Memorandum of Understanding to commission CBP employees to serve on FDA’s behalf at ports where FDA may not currently have staff or to augment FDA staff in the enforcement of FDA’s prior notice regulation. FDA plans to co-locate its Prior Notice Review Center and staff at CBP’s National Targeting Center. This will ensure that the agencies maximize their joint assets and provide consistent enforcement. It further engenders a common bond, so that the two agencies most responsible for protecting the nation’s imported food supply can interact in person.

FDA and CBP are also working together to develop enhanced information systems and programs to keep food imports secure without imposing unnecessary costs or delays. FDA and other federal agencies continue to contribute to the development of CBP’s state-of-the-art automated commercial environment system to screen products and to support FDA’s public health mission.

“Not only have FDA and the Bureau of Customs and Border Protection forged a stronger working relationship, but we have also listened carefully to stakeholders across the board to provide an unprecedented level of food security as efficiently as possible,” said Dr. McClellan. "We will continue to work with all affected parties to help them understand how to do their part in assuring food safety at the lowest possible cost.”

FDA has already begun an extensive domestic and international outreach and education about the new rules. In the coming weeks, FDA will conduct national and international meetings and other programs to provide a comprehensive picture of the rules. As part of this effort, FDA also will hold a satellite downlink public meeting on Oct. 28 to discuss the two regulations. Information about this meeting, including domestic and international viewing opportunities and registration, is available at

In another step to improve the technologies available to keep the nation’s food supply safe and secure, FDA today sent to Congress a report detailing progress it has made in research to develop rapid tests and sampling methods to improve the agency’s ability to identify contamination of food.

The report, entitled “Testing For Rapid Detection of Adulteration Of Food,” responds to provisions in Section 302(d) of the Bioterrorism Act. That section charged FDA with developing faster methods to detect adulterated foods and animal feed at U.S. ports of entry so as not to delay unduly the flow of food to domestic markets. This is the first annual report to Congress as required under the Bioterrorism Act.

“Improving FDA’s inspection, detection and monitoring capabilities of food imports is a top priority,” said Dr. McClellan. “With our research partners in private industry, other government agencies, academia, trade associations, and others, FDA is conducting a considerable amount of research intended to develop new test methods and innovative test kits. Our goal is to make them faster, more economical, and more accurate, so that we can be better prepared at a lower cost.”

According to the report, FDA currently has over 90 different active research projects involving test and sampling methodology development. This is an FDA-wide effort and involves many FDA scientific experts and partners in academia and consortia to achieve this important and strategic research goal. Some of the research highlights are provided below:

Center for Food Safety and Applied Nutrition

Developing and validating effectiveness of rapid testing technology and methods for detecting potential biological, chemical and radiological threat agents in foods
Developing and assessing processing technologies and systems that may mitigate or eliminate potential biological and chemical threats to the food supply
Center for Veterinary Medicine

Successfully validated an analytical method using polymerase chain reaction (PCR) tests to detect bovine-derived materials in animal feeds to ensure compliance with FDA’s regulation designed to protect the U.S. against bovine spongiform encephalopathy (BSE, or “mad cow disease)
Worked to expand the number of species that the current PCR method is capable of detecting from bovine to include other ruminant species.
Office of Regulatory Affairs

Developed an immunoassay method for detection of botulism toxin in food.
Developed a mass spectrometry-based method for detecting a wide variety of chemical toxins in food.
National Center for Toxicological Research

Developed a novel approach to rapidly identify biomarkers of toxicity using a mass spectrometry-based method for detecting microorganisms that could be introduced into otherwise harmless organisms to cause intentional adulteration.
“The one-time allocation of $5 million provided last July by the Office of Management and Budget is allowing FDA to strengthen this research program,” said Dr. McClellan. “Because testing select agents in food represents a new field of scientific inquiry, the research needs are quite substantial and will need to be sustained over several years.”
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Cheap, Superefficient Solar

Technologies collectively known as concentrating photovoltaics are starting to enjoy their day in the sun, thanks to advances in solar cells, which absorb light and convert it into electricity, and the mirror- or lens-based concentrator systems that focus light on them. The technology could soon make solar power as cheap as electricity from the grid.

The idea of concentrating sunlight to reduce the size of solar cells--and therefore to cut costs--has been around for decades. But interest in the technology has picked up in the past year. Last month, Japanese electronics giant Sharp Corporation showed off its new system for focusing sunlight with a fresnel lens (like the one used in lighthouses) onto superefficient solar cells, which are about twice as efficient as conventional silicon cells. Other companies, such as SolFocus, based in Palo Alto, CA, and Energy Innovations, based in Pasadena, CA, are rolling out new concentrators. And the company that supplied the long-lived photovoltaic cells for the Mars rovers, Boeing subsidiary Spectrolab, based in Sylmar, CA, is supplying more than a million cells for concentrator projects, including one in Australia that will generate enough power for 3,500 homes.

The thinking behind concentrated solar power is simple. Because energy from the sun, although abundant, is diffuse, generating one gigawatt of power (the size of a typical utility-scale plant) using traditional photovoltaics requires a four-square-mile area of silicon, says Jerry Olson, a research scientist at the National Renewable Energy Laboratory, in Golden, CO. A concentrator system, he says, would replace most of the silicon with plastic or glass lenses or metal reflectors, requiring only as much semiconductor material as it would take to cover an area the size of a typical backyard. And because decreasing the amount of semiconductor needed makes it affordable to use much more efficient types of solar cells, the total footprint of the plant, including the reflectors or lenses, would be only two to two-and-a-half square miles. (This approach is distinct from concentrated thermal solar power, which concentrates the heat from the sun to power turbines or sterling engines.)

"I'd much rather make a few square miles of plastic lenses--it would cost me less--than a few square miles of silicon solar cells," Olson says. Today solar power is still more expensive than electricity from the grid, but concentrator technology has the potential to change this. Indeed, if manufacturers can meet the challenges of ramping up production and selling, distributing, and installing the systems, their prices could easily meet prices for electricity from the grid, says solar-industry analyst Michael Rogol, managing director of Photon Consulting, in Aachen, Germany.

But the approach has been difficult to implement. "It has not delivered on the promise, mostly because of the complexity of the systems," Rogol says. The goal is to engineer a concentrating system that focuses sunlight, that tracks the movement of the sun to keep the light on the small solar cell, and that can accommodate the high heat caused by concentrating the sun's power by 500 to700 times--and to make such a system easy to manufacture.
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Tuesday, November 07, 2006

Cognitive Radio

Growing numbers of people are making a habit of toting their laptops into Starbuck's, ordering half-caf skim lattes, and plunking down in chairs to surf the Web wirelessly. That means more people are also getting used to being kicked off the Net as computers competing for bandwidth interfere with one another. It's a local effect -- within 30 to 60 meters of a transceiver -- but there's just no more space in the part of the radio spectrum designated for Wi-Fi.

Imagine, then, what happens as more devices go wireless -- not just laptops, or cell phones and BlackBerrys, but sensor networks that monitor everything from temperature in office buildings to moisture in cornfields, radio frequency ID tags that track merchandise at the local Wal-Mart, devices that monitor nursing-home patients. All these gadgets have to share a finite -- and increasingly crowded -- amount of radio spectrum.

Heather Zheng, an assistant professor of computer science at the University of California, Santa Barbara, is working on ways to allow wireless devices to more efficiently share the airwaves. The problem, she says, is not a dearth of radio spectrum; it's the way that spectrum is used.

The Federal Communications Commission in the United States, and its counterparts around the world, allocate the radio spectrum in swaths of frequency of varying widths. One band covers AM radio, another VHF television, still others cell phones, citizen's-band radio, pagers, and so on; now, just as wireless devices have begun proliferating, there's little left over to dole out.

But as anyone who has twirled a radio dial knows, not every channel in every band is always in use. In fact, the FCC has determined that, in some locations or at some times of day, 70 percent of the allocated spectrum may be sitting idle, even though it's officially spoken for.

Zheng thinks the solution lies with cognitive radios, devices that figure out which frequencies are quiet and pick one or more over which to transmit and receive data. Without careful planning, however, certain bands could still end up jammed. Zheng's answer is to teach cognitive radios to negotiate with other devices in their vicinity. In Zheng's scheme, the FCC-designated owner of the spectrum gets priority, but other devices can divvy up unused spectrum among themselves.

But negotiation between devices uses bandwidth in itself, so Zheng simplified the process. She selected a set of rules based on "game theory" -- a type of mathematical modeling often used to find the optimal solutions to economics problems -- and designed software that made the devices follow those rules. Instead of each radio's having to tell its neighbor what it's doing, it simply observes its neighbors to see if they are transmitting and makes its own decisions.
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Monday, November 06, 2006

Electricity from Sugar Water

A new way to make hydrogen directly from biomass, such as soy oil, reported in the current issue of Science, could cut the cost of electricity production using various cheap fuels.

Researchers at the University of Minnesota have developed a catalytic method for producing hydrogen from fuels such soy oil and even a mixture of glucose and water. The hydrogen could be used in solid-oxide fuel cells, which now run on hydrogen obtained from fossil-fuel sources such as natural gas, to generate electricity. Further, by adjusting the amount of oxygen injected along with the soy oil or sugar water, the method can be adapted to make synthesis gas, a combination of carbon monoxide and hydrogen that can be burned as fuel or converted into synthetic gasoline. The method can also produce chemical feedstocks, such as olefins, which can be made into plastics.

Although the results are preliminary, the new catalysis process represents a fundamentally new way to directly use soy oil and other cheap biomass as fuels; such biomass now needs to be converted into biodiesel or ethanol in order to be used as fuels. "Generally, people have steered clear of nonvolatile liquids--materials that you cannot vaporize," since these typically produce a carbon residue that stops the process of producing hydrogen, says Ted Krause, head of the basic and applied research department at Argonne National Laboratory, in Argonne, IL. By eliminating the need to process soy oil and sugar water to make volatile fuels such as ethanol, the new method "opens up the number of available biomaterial feedstocks," he says.

The process begins when the researchers spray fine droplets of soy oil or sugar water onto a super-hot catalyst made of small amounts of cerium and rhodium. The rapid heating combined with catalyst-assisted reactions prevents the formation of carbon sludge that would otherwise deactivate the catalyst. And the reactions produce heat, keeping the catalyst hot enough to continue the reaction. As a result, although fossil fuels are used initially to bring the catalysts up to the 800 °C working temperature, no fossil fuels are needed to continue the process. "One of the virtues of our process is it requires no external process heat--it drives itself," says chemical-engineering and materials-science professor Lanny Schmidt, who led the research.
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Super-vivid, super-efficient displays

Your next MP3 player may sport more-vivid color displays and longer-lasting batteries. That's because a major manufacturing effort by South Korea's Samsung SDI could help bring a display technology called organic light-emitting diodes, or OLEDs, into the mainstream. Until now, OLED displays have not been manufactured in high volumes, and applications have generally been limited to Asian markets.

OLEDs are based on a light-emitting conductive organic molecules that consumes one-half to one-fifth of the power of liquid-crystal displays (LCDs). Displays using OLEDs present more-vivid colors and allow for clearer videos, thanks to a faster "refresh rate." As the technology matures and cheapens, it could ultimately replace current computer-monitor and television technologies.

While other electronics companies are in the planning stages for ramping up manufacture and adoption of OLEDs, Samsung is spending $500 million to build an OLED factory that will begin production next year. Samsung hopes to churn out between one million and two million displays per month, initially for cell phones and other mobile devices that would move beyond Asian markets, says Barry Young, an industry analyst.

The Samsung effort (see Samsung's technology explainer here) includes technology from Universal Display, of Princeton, NJ, which pioneered an OLED variant that uses phosphorescent molecules to produce the reds, blues, and greens necessary for a color display with very high efficiency.

Stephen Forrest, vice president of research at the University of Michigan, whose research group (originally at Princeton University) licensed its OLED technology exclusively to Universal Display, believes the Samsung factory is a huge milestone. "We are at a very critical frontier," he says. "This is a good technology, and people know it, so now it's a matter of getting more companies committed to entering into manufacturing. To make a better, cheaper, more efficient display is a very important part of our everyday life."
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LED Driver Supports Multi-Mode Operation

Catalyst Semiconductor’s high-power, 500-mA inductive boost LED driver is designed for Movie/Flash mode applications. The CAT4134 offers a fully integrated Movie/Flash switching function, which allows designers to set the exact Flash and Movie modes required via a single resistor, minimizing the need for external circuitry. Capable of driving up to six white/color LEDs, the CAT4134 is ideal for increasing efficiency and simplifying the design of video lighting applications.

The new Catalyst inductive boost LED driver offers dual channel outputs, which provide matched LED currents of up to 250 mA per channel. Output current levels are controlled by one of two resistors, RSET or RFLASH. When the flash input pin is low (Movie mode), RSET controls the LED current. When the flash input pin is high (Flash mode), the resistor RFLASH controls the LED current. Each channel drives two or three white LEDs in series and provides a regulated current to control LED brightness. Input supply down to 3 V is supported, making the device ideal for Li-Ion battery applications.

High frequency, low noise operation allows the CAT4134 to be used with small external inductors and ceramic capacitors while retaining up to 85% efficiency. When disabled the device can be placed into a “Zero” quiescent mode via a shutdown pin, eliminating battery drain when not in use.

The CAT4134 is available in a 3-mm x 3-mm, 12-pin TDFN RoHS-compliant package. Pricing for 10,000-piece quantities is $0.88 each. Samples and evaluation kits are now available.
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Friday, November 03, 2006

Thermal Solutions Provider Licenses Heat Transfer Technologies

Celsia Technologies has entered a multi-year agreement with Taiwan-based Yeh-Chiang Technology (YCTC), a manufacturer of heat pipes. Under the terms of the agreement, YCTC will manufacture Celsia’s thermal management products in China. YCTC will also license Celsia’s patented thermofluidic technology to offer to its key OEM customers.

“Celsia’s technology is exactly what the market needs today,” said John Yang, founder of YCTC. “With Celsia’s new vapor chamber technology and its thin, flat form factors, customers can have greater flexibility and simplicity in their electronic designs and assemblies. We believe this technology is the next step for electronics heat transfer, and it will provide great differentiation to our customers.”

“We are building partnerships across the electronics supply chain so that in addition to our strong technical position, Celsia is equally strong in its distribution and supply network,” said George Meyer, Celsia’s chief marketing officer and general manager of the Americas and Europe. “YCTC is an excellent heat pipe manufacturer with a laser focus on manufacturing two phase heat transfer products. The combination of Celsia technology and YCTC manufacturing will be a formidable force in the market.
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Thursday, November 02, 2006

Rerouting Brain Circuits with Implanted Chips

New, implantable and wireless brain chip can create artificial connections between different parts of the brain, paving the way for devices that could reconnect damaged neural circuits. Scientists say the chip sheds light on the brain's innate ability to rewire itself, and it could help explain our capacity to learn and remember new information.

"We have a chance of manipulating and repairing [specific] regions of the brain that might be damaged," says Joseph Pancrazio, director of the neural-engineering program at the National Institute of Neurological Disorders and Stroke in Bethesda, MD. "To be able to repair these kinds of lesions on a neuron-by-neuron basis is extraordinary."

In stroke and spinal-cord injuries, neural circuits may be damaged, leaving patients with profound problems in movement or speech. In recent years, scientists have begun developing brain-cognitive interfaces, which record neural signals and transmit them either to a computer, to another part of the brain, or to another body part in effort to get around the neural blockade.

In the new study, researchers from the University of Washington, in Seattle, showed for the first time in live animals that an implantable device could record signals from one part of the brain and transmit that information to another part, reshaping neural connections in the process. "We essentially set up an artificial-feedback loop between two different parts of the cortex," says Eberhard Fetz, the scientist who led the study.

The device, built entirely of off-the-shelf parts, consists of tiny wire electrodes surgically implanted into a monkey's motor cortex. (Neurons in this area are active when an animal makes a voluntary movement.) The wires record activity from these cells and send the signals to a tiny printed circuit board, which amplifies and processes the signal. That information is then sent to a neighboring circuit board and electrode, which uses the signal to stimulate cells in another part of the motor cortex. The entire apparatus is encased in titanium and attached to the monkey's head, allowing the animal to go about its normal daily activities.

According to research published online in Nature, the device was able to reshape the neural circuits that control muscle movement. At the start of the experiment, neurons at the recording sites triggered movement of the wrist in a different direction than when neurons at the stimulating site were activated. After running the record-stimulate sequence for 24 hours in freely behaving monkeys, researchers found that underlying neural circuits had changed: the wrist movement associated with neurons at the stimulating site more closely resembled the movement associated with neurons at the recording area, indicating that the neural connections between these two areas had strengthened.

The findings support a long-held theory in neuroscience: that activating different brain cells at the same time strengthens connections between those cells. Scientists believe this concept underlies our ability to both learn new information and recover some motor and cognitive function after strokes and other brain injuries. "The findings show that the current conception of long-term strengthening is very much on the right track," says Krishna Shenoy, a neuroscientist at Stanford who is also developing neural implants
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TPS40140 Synchronous PWM Controller

Although new technologies based on digital power control promise to be disruptive technologies in the long run, mainstream analog control technology can still have a significant and immediate impact on power system designs. Such can be said for this year's Power Electronics Technology Product of the Year award winner. The TPS40140 synchronous PWM controller from Texas Instruments (TI) is, at heart, an analog controller. However, because of its clever design techniques, the chip simplifies the potentially complex task of paralleling voltage sources to create scalable point-of-load (POL) power designs.

The TPS40140 features a unique characteristic that the vendor calls “stackability.” That term describes the way multiple controller ICs can be combined in a single design either to scale current levels on a given output or to add additional voltages. A single TPS40140 can be configured to generate two independent outputs or configured as a 2-phase controller with a single output. Then, by stacking or paralleling controller chips, designers can increase current output on a given voltage rail. The controller supports up to 16 phases of interleaved operation for up to 320 A of output.

The resulting design can be a mix of single- and multi-phase outputs (see the figure). Interleaved operation not only permits the scaling of current levels, but also reduces ripple current and requirements for input and output capacitance.

Although existing multiphase controllers can be cascaded to scale the number of phases, they typically employ an analog interface to control phasing of the different outputs. In contrast, the TPS40140 employs a unique digital interface to control phasing, which makes the designs less sensitive to noise and eases pc-board layout.

In a multicontroller, multiphase design, one channel generates a master clock (CLKIO). This clock is distributed to the slave channels, which use it to generate their PWM clocks. The master clock runs at eight times the frequency of the slave PWM clock. In other words, within each master clock signal there are eight frames (seven clock pulses plus a missing pulse for synchronization), and each PWM slave clock will trigger on a different frame depending on the phase number assigned to that PWM channel. That phase number is programmed using a simple voltage divider connected to the phase select pin on each channel.

In designing this part, TI overcame several design challenges. According to Stefan W. Wiktor, dc-dc controller design manager at TI, one of the most difficult was achieving good current balance among phases when the phases are generated across multiple controller chips. This is because of the difficulty in matching PWM ramp signals from chip to chip. TI addressed this problem using a frequency-to-current converter that makes the PWM ramp signal independent of semiconductor process-related parameters, except for reference voltage, which is very controllable.

Though just introduced in August 2006, the TPS40140 has already experienced design wins at two major power-supply companies, a large server manufacturer and a test equipment manufacturer. However, Tim Goodrow, product marketing manager for dc-dc modules at TI, observes that customers are adopting the TPS40140 because of the ease with which this controller implements multiphase control, more so than for its flexibility in generating multiple voltages.
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Wednesday, November 01, 2006

Rectifier IC boosts

Increasing system efficiency by 1% over discrete solutions, the IR1166 SmartRectifier IC simplifies the design of mid-power secondary synchronous rectification (SR) circuits of resonant half-bridge converters and flyback converters designed for 50 to 150-W discontinuous conduction mode, critical conduction mode, and continuous conduction mode. The part uses a technique for precise, direct sensing of voltage thresholds across the SR MOSFETs.

Specifications include a VCC of 20 V, a VFET of 200 V, a maximum switching frequency of 500 kHz, a gate drive of 1/–3.5 A, a VGATE clamp voltage of 10.7 V, and a maximum sleep current of 200 µA. The part is housed in an SO-8 package and will soon be in a DIP-8 package. The IRAC116-100W flyback reference design is also available. ($0.70 ea/10,000—available now.)
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