Power management solutions improve operating time in mobile handsets

July 26, 2010

Written by Wayne Seto, Technical Marketing Manager

With the proliferation of cellular mobile handsets, especially smartphones, in the world today where people are connected 24/7, consumers just can’t seem to get enough of the voice calls, emails, text messages and surfing the web. However, all of these activities greatly consume battery life in our handsets; as such, our handhelds lead to that one-bar battery power indicator very quickly. In this article from the June 1, 2010 edition of EDN Asia, Wayne Seto discusses what can be done to prolong the battery life for these handsets so that we can use them longer.

Read the complete article

Tags: efficiency, Energy Efficiency, Fairchild Semiconductor, power management

Reliable Reliability

July 20, 2010

  With an IQ of 181, you might think it’s hard for me to amuse myself, but it’s not true. I like a little light reading in the evening…things like Kreck and Lück’s The Novikov Conjecture (A group G is a-T-menable, or, equivalently, has the Haagerup property if G admits a metrically proper isometric action on some affine Hilbert space, page 205) or Carver Mead’s Collective Electrodynamics (Because the system spatial attributes of the system in an eigenstate are stationary, the system in an eigenstate cannot radiate energy, page 106.)

 Fascinating, riveting stuff, I’m sure you agree.

 This led me to think a little bit about semiconductor reliability, though I confess my thinking might have been influenced by the consumption of a bottle of Puligny Montrachet Grand Cru Domaine des Comtes Lafon. In case you’re unfamiliar, that’s a wine very similar in appearance to the Franzia Crisp White wine you can buy in a box at the local market.

 I mentioned Carver Mead above. Among his many accomplishments, he was the guy who contributed to Moore’s Law (which says transistor density on an integrated circuit will approximately double every two years) when Gordon Moore worked at Fairchild Semiconductor in the 1960s.

 In 1965, Gordon had just started making his plots, where he’d plot the logarithm of the number of transistors on a chip as a function of the year. They’re little hand-drawn plots. I still have some around. One day we were talking about his plots. He said “You’re working on electron tunneling that happens when things get really small, right?” Yeah. “Well, wouldn’t that limit how small you can make a transistor?” Yes. “Well, how small is that?” Gordon has a way of asking these very simple questions that you really think you should know the answer to, and I didn’t. I said, well, I have to go and think about it. I’ve been thinking about it ever since. Carver Mead, from a speech at Telecosm 2006

 The driver for Moore’s Law is the fact that as we make transistors smaller, they get cheaper to manufacture AND they work better. Isn’t that something? They work better. Think about that. And, what do we mean by working better? They consume less power and they can switch more quickly. This is the small miracle that fuels the marvelous advances of the digital revolution.

 Today Fairchild is a leader in power management and mobile technology and in our factories, over 50 years after Fairchild Semiconductor was originally formed, we continue to take advantage of the state-of-the-art in transistor lithography.

 There are not many businesses like ours where customers expect continuous improvement in products-with lower prices every year. Generally, if you buy the bargain brand at the big-box discount store, you expect lower quality…fewer features and less reliability. If you buy an inexpensive car, you expect it to be less comfortable and less reliable than a premium brand. But, that’s not how the semiconductor business works. Regardless of what you pay for our product, you expect high reliability…robust and rugged components.

 Year-by-year, we practice continuous improvement and do our part to produce parts with very low failure rates. As a semi-random example, we publish a 3.65 FIT (Failure in Time) rating for the n-channel FET NDT3055. This works out to one failure for 3,127 years of operation.

 Let’s take a closer look at what this means. We can’t build up a significantly significant number of parts and test them for 3,127 years. We’d love to, but we can’t. The FIT rating is based on accelerated testing of sample parts with numbers plugged into a formula.

 The basic idea is that by aging sample devices with high humidity and overvoltage stress, we can estimate the failure rate without waiting for tens of thousands of years.

 As I mentioned above, we do our part to create robust devices for our customers. However, is there also a role for the customer? Of course there is.

 In building up our reliability estimate, we use a temperature stress factor adapted from the Arrhenius equation-which includes this term:

eEa/k(1/Tu - 1/Ts)

Where:

Ea = Semiconductor activation energy

k = Boltzmann’s Constant

Tu = use temperature (K), or the die temperature in the design.

Ts = stress temperature (K) used in the accelerated life test.

 We control the stress temperature and it is based on the semiconductor process, generally either 150 degrees C (423K) or 175 degrees C (448K). You control the use temperature. Lower operating temperatures result in higher reliability. That’s your part of the job.

 So, let’s say you want to increase the reliability of a system. Using the free MTBF tool referenced at the end of this blog, we can see the predicted effect of reducing the operating temperature from 100 degrees C to 90 degrees C.

 At 100C, the calculated FIT is 1009.

At 90C, the calculated FIT is 860.

Is that enough of an improvment? That depends on your needs.

Please note I am not saying anything about the fundamental reality of these numbers. They are numbers, but there is a fair amount of speculation and unconsidered factors in a real life design.

 It’s getting late and I notice there is about a half a glass left in the bottle. I suppose I could put the cork back in and save that last bit for later.

 Or not.

 The unpublished papers referenced below are available by request.

 The author would like to thank Thomas Welch and Raymond Oakley who collectively contributed three unhelpful suggestions and two rude comments during the writing of this article.

 References

On Acceleration Factors used in Failure Rate Prediction - Unpublished paper by Thomas Welch, Director, Quality and Reliability, Fairchild Semiconductor

Secrets of Mean Time Between Failure - Unpublished paper by Raymond Oakley, Staff Customer Quality Engineer, Fairchild Semiconductor

Free MTBF tool from Advanced Logistics Developments, Free MTBF Tool

Failure Mechanisms and Models for Semiconductor Devices, JEDEC Publication, JEP122E

Reliability by Design, A. C. Brombacher, John Wiley and Sons

Reliability, Maintainability and Availability Assessment, Mitchell O. Locks, Hayden Book Company

Collective Electrodynamics, Carver A. Mead, The MIT Press

The Novikov Conjecture, Matthias Kreck and Wolfgang Lück, Birkhauser Verlag

Tags: Dr. FAE, Fairchild Semiconductor, reliability, semiconductors

Would you care for an IC?

May 7, 2010

Instead of answering one of the many technical questions that cross my desk, I hope you’ll indulge me while I digress to tell you about the party I attended in Manhattan last week. Perhaps you saw pictures from this gathering…it was hosted by the widow of a moderately infamous oil mogul and many of the single-name-only crowd were there: Angie and Brad, Jewel, Cher, Sting, Jen, Björk, Moby and others, as were a random collection of B-list partiers…rappers, lobbyists, literary agents, fashion models….and the ever-present John Q. Fields-you know, the ubiquitous actor with the very high IQ (but not quite so high as mine, thank you very much).

The first thing you’ll want to know is how an engineer gets an invitation to a party like this, but I can’t help you. That’s a path you’ll have to blaze on your own.

After a stare-down with the bartender who tried to insult me with an exceptionally average Cognac when, from a prior visit to this expansive apartment, I knew there was a bottle of Cognac Dudognon Héritage HENRI IV hidden in a secret storage nook behind the hallway Matisse print (Woman with a Hat, or rather, an inept counterfeit). I was minding my own business by the fireplace when a pretty TV actress planted the heel of one of her Jimmy Choo slingbacks directly on my instep. After accepting her profuse apology, we struck up a conversation and she asked what I do for a living.

“I work for a semiconductor company…a famous one with a long history of accomplishment and invention.” But it had no meaning or relevance to her. She looked at me as if I was speaking in tongues-until I explained.

“Unless you’re an electrical engineer, you might not be familiar with Fairchild Semiconductor, but it’s highly likely that you own many of our products. For example, do you own a brand name flatscreen TV? Then, most likely, you own numerous Fairchild components. Do you have a game console? The most popular ones are built with Fairchild parts. Do you drive a car with a navigation system? Do you have a cell phone with a digital still camera? Do you have a DVR? A computer? An Energy Star® air conditioner or washing machine? A printer? A music player? We’re everywhere and you are our customer! Your life is probably overflowing with hundreds of our tiny, energy-saving, feature-enhancing components. You might not know our name, but we reduce the energy consumption of your computer, provide the backlighting for your LCD TV, increase the talk time on your cell phone, and generally power your world.”

As you might imagine, she swooned-and peppered me with questions about our support for soon-to-be-released cell phone features and enhancements, which I will share later.

Then, eavesdroppers quickly spread the word. Many stopped by to shake my hand and kiss my cheek…and thank me for our contributions to their way of life…for helping to create and power all the beautiful things that enrich and enable our fabulous modern lifestyle.

Snifters of the secret stash of cognac finally came my way, but I could hardly find a quiet moment to enjoy a sip.

Oh, my friends, celebrity can be such a heavy burden.

But, have no worry.

I can handle it.

I’ll be fine.

Tags: Dr. FAE, energy-saving device, Fairchild Semiconductor, feature-enhancing components

Using high-voltage backlight inverters for better LCD TV performance

April 2, 2010

The adaptation of digital broadcasting throughout the world is offering consumers the screen resolution that they have not experienced before with CRT TV.

Digital broadcasting offers higher resolution, no motion blurring, larger panel size and lower price - features that consumers are demanding today. And the LCD TV is the next generation of appliances to benefit from the features of digital broadcasting.

The adoption of high-voltage backlight inverters, instead of the existing low-voltage backlight inverter, is one way to enhance the performance of LCD TVs and reduce total system cost.

The advantage of using a high-voltage backlighting inverter is that it can be connected to the power factor correction (PFC) directly without a DC-DC converter, while the low-voltage backlight inverter requires a DC-DC converter after the PFC stage. In fact, the DC-DC converter used with high-voltage backlight solutions to power other loads needs to process only around 30% of the total LCD TV power, because the typical power consumption of the backlight unit in an LCD TV power is 70% of the total. As a result, the high voltage solution reduces the cost of the transformer and the MOSFET in the DC-DC converter.

A half-bridge topology is typically used in high-voltage inverters. However, because it is difficult to achieve Zero Voltage Switching (ZVS) with the half-bridge for every condition, blocking diodes are usually connected in series with the MOSFETs and fast recovery diodes (FRD) are connected in parallel.

MOSFETs have built-in diodes, but if the half bridge circuit does not operate at the ZVS condition, then the reverse recovery current of the built-in diode flows into the other MOSFET when that MOSFET is turned on. This generates a tremendous amount of heat (through R_DS(ON)), and the resulting higher temperature will make the reverse recovery current in the second MOSFET even greater when it turns off. Then that high reverse recovery current will increase the power dissipation and reverse recovery current in the first MOSFET in the same way.

This positive feedback increases the MOSFET’s temperature until the amount of emitted heat equals the amount of generated heat.

Generally, the built-in diode of a typical MOSFET has a large reverse recovery current, so LCD TV makers use the half bridge solution with blocking diodes in series to prevent the built-in diode from conducting.

A solution to resolve the power consumption design issues in LCD TVs can be the Ultra FRFET™, a MOSFET with a lifetime control process of reverse recovery current.

Some advantages of using the Ultra FRFET are:

• Soft reverse recovery characteristics
• Small reverse recovery current which maintains good EMI performance in LCD TV applications
• Reduced switching loss (both turn on and off) due to low Q_g
• Supports high diode dv/dt immunity (20V/ns) compared to normal MOSFET (4.5V/ns)
• Good reliability at high temperatures and high frequency operation

The Ultra FRFET works well without blocking diodes and FRDs in LCD TV high voltage backlight inverter applications and is suitable for dimmable ballast applications.

Tags: digital broadcasting, Fairchild Semiconductor, high-voltage backlight inverters, LCD TV performance, MOSFETs, reverse recovery current, Ultra FRFET

Power Supplies Get Greener

January 18, 2010

Each quarter, Fairchild Semiconductor introduces new products, tips and tools for power and analog applications in the quarterly Benchmarks magazine. The following Benchmarks Volume 1, 2010 “Engineering Connections” article discusses flyback topology as an efficient solution for meeting today’s global demand for lowering power consumption in power supplies.

External power adapters are instrumental for the operation of virtually all small electronic devices. As many as 3.2 billion adapters are currently in use globally, according to industry estimates.

With this worldwide focus on energy savings, regulatory bodies are examining all ways to “go green,” and standards have been developed, specifying higher levels of efficiency for products such as notebook PC power supplies. Flyback topology has proven to be an effective solution, both in terms of cost and technology, for pulse-width modulated (PWM) power conversion in these products. Fairchild has a wide portfolio of PWM controllers  that enhance the performance of flyback converters.

As part of its global focus on energy savings, Fairchild has developed a portfolio of pulse-width modulated (PWM) controllers, which enable notebook power-supply designers to meet the stringent international energy-saving regulations. These include the ENERGY STAR External Power Supply (EPS) version 2.0 requirement that mandates 87 percent average active-mode efficiency to obtain compliance.

Integrated PWM controllers, like the FAN6754, offer designers high-voltage startup to improve energy savings at light load by 25 percent when compared to alternate solutions. It also eliminates external protection circuits by incorporating over-voltage, over-current and over-temperature protection plus brownout and line-compensation functions. Other advantages of Fairchild’s PWM controllers include frequency hopping, which reduces EMI emissions by as much as 5-10 dB, and internal soft start (8ms) to reduce voltage stress on the MOSFET at startup.

Additionally, Fairchild’s PWM controllers incorporate several design features that lower the overall power consumption of notebook adapters, such as a proprietary green-mode function that provides off-time modulation to continuously decrease the switching frequency under light-load conditions. Fairchild’s PWM devices offer a host of robust, accurate protection features built-in to protect the power supply and the load from failure, all without adding external components or circuitry.

Tags: Benchmarks, Energy Efficiency, Fairchild Semiconductor, flyback converter, green, PWM controller

What should we do to achieve high efficiency and power in LED street lamps ?

December 21, 2009

The power requirement of LED street lamps being used in China falls in the range of 100~250W. It is widely agreed that if used properly, these kinds of LED street lamps deliver many advantages. What I want to explain here is the ways to make it possible for these lamps to deliver those advantages. The key factors to be considered are high efficiency, power, reliability and cost-effectiveness.

Some low-power lighting requires PFC, while high-power lamps usually require PFC combined with DC/DC requirements. In China where the AC line voltage is 220V, Boundary-Conduction Mode (BCM) PFC controllers, such as the FAN7530 and the FAN6961, become the ideal choice to maintain a balance between the efficiency and performance-cost ratio. These solutions only need a few components.

Low Rds(on) SupreMOS(TM) MOSFETs, can further decrease switch and conduction loss. When used at the boost output, the HyperFAST 2 high voltage diode family with lower Vf can also lower the conduction loss of the diode itself.

For DC/DC topology, there are many choices such as quasi-resonant (QR), double transistor forward (DTF), active-clamp, LLC and asymmetrical half-bridge (AHB). High-power lighting applications, for example in a 100W lamp, where the output voltage is usually a little high, QR working with a synchronous rectifier can achieve up to 92.5% of total efficiency. Moreover, Fairchild has integrated QR and BCM PFC into one package (the FAN6921), reducing external components and simplifying the control.

Another popular topology is zero voltage switch (ZVS). Both an LLC and an AHB can have their two bridges working in zero voltage by implementing a simple circuit. When using Fairchild’s highly-integrated solution (for example, a LLC controller and two MOSFETs in FSFR; an AHB controller and two MOSFETs in FSFA2100), the circuit can be further simplified, with few external components. And the body diode of the MOSFET has good fast recovery characteristic, which can reduce the possibility of short-through, yet provide high reliability with high efficiency. When the output voltage is high, an LLC is the better option; when the output voltage is low, an AHB is more suitable for implementing a self-driven synchronous rectifier, and both can achieve over 93~94% efficiency.

The above solutions are highly integrated solutions and require just a few components, thus delivering high efficiency, high power density, optimized thermal performance as well as high reliability.

Click here for more information on LED lighting from Fairchild.

Tags: Energy Efficiency, Fairchild Semiconductor, LED Lighting

Perfect Sunrise, Great location, Wonderful people.

August 3, 2009

Arriving at Fort Williams in Cape Elizabeth, Maine on Saturday for the 12th TD Banknorth Beach to Beacon 10K, my breath was taken away. This didn’t happen from physical exertion but from the majestic beauty of the sunrise over the beautiful rocky coast. I had a feeling that this meant it would be a memorable day.

When the race started, we knew that people from all over the world and over 50 of our own employees were running the picturesque course. Anticipation rose as we awaited the arrival of the first finishers.

At first the runners trickled in but soon the field was flooded with participants of all ages. We congratulated everyone on their successful completion and were excited to spot the green shirts of our co-workers. The Fairchild Semiconductor men ended up finishing #2 in the men’s corporate challenge! Congrats guys!

In our Green Energy Sponsor tent, we had fun mingling with interested community members who took home free give-aways like green water bottles. Visitors of all ages rode the bicycle to charge their cell phone.

When I left at the end of the event, I thought how amazing the day was- perfect sunrise, great location, wonderful people!

A big thanks to my fellow employees at Fairchild Semiconductor who ran and helped man our Green Energy Sponsor booth. Our contributions will go to the 2009 beneficiary, Maine Handicapped Skiing. Thanks to everyone at Fairchild who made our Green Energy Sponsorship a success!

Tags: Fairchild, Fairchild Semiconductor, green, sponsor

Engineers on the Run

July 17, 2009

If you drove by the South Portland, Maine corporate site, on July 15, 2009, you may have been surprised to see a fleet of engineers running! Yes…that was us and one of Maine’s most recognized celebrities- Joan Benoit-Samuelson, the first Olympic Gold Medalist for the Women’s Marathon in 1984.

Joan led us for a memorable fun run to cap off the day! Prior to the run, Joan, who is also the founder of the Beach to Beacon 10k Road Race, thanked us for being the first Green Energy Sponsor of the race this year. Our sponsorship enables the race to expand its Green Program, which will include recycling, composting, using eco-friendly portable toilets, recycling shoes and paperless communications for the race.

On August 1, 2009, at the TD Banknorth Beach To Beacon 10k, you will see engineers on the run again! Over 50 of our employees are participants in the race, as well as many additional volunteers who will be manning our booth and helping facilitate the race.

Tags: Beach to Beacon, engineers, Fairchild Semiconductor, green energy sponsor, recycling

Cell Phone Connection Failed – AGAIN!?

July 17, 2009

Standing in the park, I have been checking emails, making phone calls and taking a few precious pictures of my darling dog. Wishing to send the pictures to a friend’s cell phone, I press the button and stare at the cell phone display. Suddenly, it says “connection failed.” What! I try again and realize that the cell phone battery is too low with barely one bar showing.

Does this sound familiar to you?

We all want to be connected via cell phone whenever and wherever we are. Unfortunately, our cell phone battery does not always keep up with our busy lifestyle.

Inside of every cell phone is a radio frequency (RF) transmitter. Every time you talk, text or send data, the transmitter drains power from the battery. Often the transmitter consumes only 10% of the phone’s total power. However, if you’re in a poor coverage location, surf the net or up-load photo/video, the transmitter’s battery consumption can top six times, sapping 60% of the battery’s charge. This transmitter can be a huge power drain and dramatically reduce your talk time on the cell phone.

Today’s feature-rich 3G phones require more power than ever before. The design challenge facing engineers today is how to improve efficiency in existing areas such as RFPA, display and increased talk time so more power is available for new features.

One solution is to install a step down DC-DC converter with dynamic voltage scaling to control V_OUT between the battery and the RF Power Amplifier (RFPA). This reduces current consumption by 30-50%, and makes power available for other functions (such as MP3, GPS and video). In addition to reducing current consumption, a step down DC-DC converter also reduces heat and increases talk time.

If you would like to check out Fairchild’s solution, please watch a short video demonstrating a solution to extend battery power for a 3G phone by improving the efficiency of the RFPA. More information on RF Power is available at www.fairchildsemi.com/rfpower.

Tags: battery life, cell phone, DC-DC converter, Fairchild, Fairchild Semiconductor, power, RF Power Amplifier, RF transmitter

The Race for Highest System Efficiency

June 15, 2009

By Guy Moxey, Low Voltage Power, Product Marketing

With the emergence of important climate saving legislation such as 80 PLUS, Climate Savers and EnergyStar® 5, analog designers for DC-DC power systems are striving to meet the challenge of increasing system level efficiency across all operating power states. From this, power silicon products such as power IC’s and power MOSFET’s are now very much in vogue as these devices create and dissipate the vast majority of any low voltage power conversion in-circuit losses that, in turn, directly relate to the system’s overall efficiency.

Take a typical notebook, typical peak efficiencies for a 46A, 2 phase Notebook VCORE solution with PWM controller and discrete MOSFET implementation are typically @90% peak at current ratings of 10A per phase, reducing down to @86% at full loads of 23A. This 10-13% loss in system efficiency is directly proportional to power and thermal dissipation. The complete notebook system is normally @ 50-60W output and running at 85% efficiency so that translates to a 9W power waste for every note book PC in the form of heat and battery life.

At start up or during a heavy processing sequence, the power system is dominated by conduction losses ( I2R) of the low side MOSFET. Here select a ultra high cell density low RDS(ON) FET housed in a dual sided cooled package so that the losses will be significantly minimized. However, as most PC s spend a majority of their operating life in standby or sleep states, it’s essential that the power system allows for light load efficiency management where gate drive and switching losses are predominant at low output currents below 10A. Here driver impedance and MOSFETs have to be carefully optimized. Gate drive voltages of 5V are preferred with MOSFETs with ultra low gate charge.

By careful MOSFET selection, close optimization with the driver IC, the design can start to move toward a higher level of overall system efficiency. Full load thermal design points can inch upward toward the 90% level, medium to light load levels can be touching 95% and ultra light loads don’t immediately take a dive southward with such velocity. But while we progress and save a few watts of loss over today’s designs, there is still some significant silicon research and development to be done before the utopian power curve can be seen.

Tags: DC-DC power systems, Energy Efficiency, Fairchild Semiconductor, MOSFETs, power IC’s