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Interested in achieving extended battery life in portable measurement applications?

MaryMcAuliffe — Wed, 22 May 2013 18:48:20 GMT

Blog by William Cooper

Interested in achieving extended battery life in portable measurement applications? Give our MSP430AFE2xx devices a try!

Cable equalization 101 – Automating your design

Hooman Hashemi — Tue, 21 May 2013 22:47:00 GMT

Judging by the number of views on a post related to numerical cable equalization, on the High Speed E2E forum (more than 3,700 at last count!), I would guess that it’s a pretty interesting topic for many folks. Since TI is one of the leading manufacturers of current feedback amplifiers (CFA), the workhorses for cable equalization, this two-part blog is devoted to giving you everything you need to implement your custom design, with a list of best devices to use and simulation techniques to boot. In this post, I will present some background information on equalization and a spreadsheet that allows you to automate the design. In part 2, we will use TINA to simulate the design and look into methods of improving the stability of the stage.

Xavier Ramus, a frequent contributor to Analog Wire, does a great job in his Application Note, A Numerical Solution to an Analog Problem, of explaining how to use a spreadsheet like Excel to do the hard work of placing the poles and zeros of Figure 1 high frequency (HF) gain boost banks (R_A, C_A, etc.) at the right frequencies to match the cable so that the cable + amplifier exhibits a flat frequency response. The reason this task is not trivial is these poles and zeros interact with each other if they are spaced close enough, making it difficult to “tune” the total arrangement. With the spreadsheet you can manipulate the component values and see their effect instantaneously.

Figure 1: Typical equalizer schematic where R_A, C_A, etc. boost gain at high frequency

In the below Excel file, I have implemented the spreadsheet that Xavier has explained. It is set up for four boost banks (R_1, C_1 through R_4, C_4) capable of 25dB of boost. For more boost or longer cable lengths, you can cascade more identical stages. The spreadsheet has an entry for the number of stages “N” in cell M6, default set to “2”. This enables you to increase the total boost (e.g. 50dB of boost for two cascaded stages, etc.) for longer cables. For additional information, check out the below PowerPoint.

(Please visit the site to view this file)

Earlier I mentioned that CFA is the architecture of choice for an equalizer. The reason is that the high frequency noise gain (1+R_F/Z_G where Z_Gis the total impedance from the inverting input to ground) increase that you need for equalization has much less unwanted impact on loop gain (and subsequently closed loop response) for a CFA than for the traditional voltage feedback topology. Furthermore, a CFA with lower internal buffer output impedance (R_I,see OA-13) holds an advantage because of the same reason. Table 1 below is a list of TI CFA amplifiers with pertinent specs, ordered from lowest R_I to highest:

Device	Devices / Package	R_I (Ω)	R_Fnominal (Ω)	Large Signal BW (Av=+2) (MHz)	Slew Rate (V/µs)	Max Supply Current / channel (mA)	Supply Rails Range (V)	Output Current (mA)	Packages	TINA Model?	1k price ($)
THS3201	1	11	768	880	6,700	18	6.6-15	100	SOT23 SOIC-8 VSSOP-8 MSOP-8	Y	1.95
THS3001	1	15	1k	300	6,500	9	9-33	120	SOIC-8 MSOP-8	Y	3.38
OPA695	1	29	402	450	4,300	13.3	5-12	120	SOT23 SOIC-8 VSSOP-8	Y	1.48
OPA2695	2	29	402	400	2,900	13.3	3.5-12	120	SOIC-8 QFN-16	Y	2.98
LMH6733	3	30	390	1,000	3,750	7.3	3-12	80	SOIC-16	Y	2.47
LMH6738	3	30	549	400	3,300	11.7	10-12	90	SOIC-16	Y	2.60
OPA694	1	30	402	675	1,700	6	7-12.6	80	SOT23 SOIC-8	Y	1.38
OPA2694	2	30	402	670	1,700	6	7-12.6	70	SOIC-8	Y	2.58
LMH6703	1	30	560	750	4,200	12.5	8-12	90	SOT23 SOIC-8	Y	1.35
OPA3695	3	37	402	440	1,700	13.3	3.5-12	120	SSOP-16	Y	3.73
LMH6714 / LMH6722	1/ 4	180	390	400	1,800	7.5	10-12	70	SOT23 SOIC TSSOP WSON SOIC	Y	0.73 1.41
LMH6723/ LMH6724	1/ 2	500	1.2k	100	600	1.4	5-12	110	SOT23 SOIC-8	Y	0.79/ 1.00
LMH6702	1	N/A	237	720	3,100	16.1	10-12	80	SOT23 SOIC-8	Y	1.45

Table 1: TI High speed CFA portfolio

Once you’ve selected a proper device from Table 1, enter its recommended feedback resistor “R_F nominal” value in Excel cell C6. To get your design (Excel row 6 final values), follow the instructions in the PowerPoint file (pages 4-9) and use Excel Solver function to minimize the difference between the computed response of your amplifier from the computed attenuation of your cable (the Excel file is already set up for that in Column P). You can find “minimize” (called “min”) in Excel under data > solver. The solver function does this by manipulating the values of gain elements in row 6 to find the best solution. You do this at low frequency and work your way up to the highest frequency of interest, and when you’re done you will end up with a plot in Excel, such as the one in Figure 2 where the amplifier response overlaps the cable attenuation plot (up to 100MHz and with ~55dB of boost from 2 identical cascaded stages).

Figure 2: Amplifier gain superimposed on cable loss

This allows you to equalize the losses in your cable for a flat overall (cable and amplifier) response. Figure 3 shows the schematic of the circuit designed by Excel:

Figure 3: Excel Solution_ One of Two LMH6733 Stages Used as Cable Equalizer

Stay tuned for Part 2, where I will discuss how TINA can be used to simulate this circuit in order to shed more light on its stability. In the meantime, please use the comments field below to fill me in on some of your biggest challenges with numerical cable equalization. Also, let me know if you found this useful and if there is additional information you feel I should cover in Part 2 of this 101.

Grounding Principles

Bruce Trump — Tue, 21 May 2013 17:26:00 GMT

In a previous blog on supply bypassing, I cautioned that poor bypassing could increase distortion of an amplifier. A reader, Walter, asked an interesting question… where should you connect the ground of a bypass capacitor to avoid problems?

This raises questions regarding proper grounding techniques. Wow. Big topic, but I may be able provide some insight with a couple of simple examples.

Figure 1 shows inverting and non-inverting amplifier stages with unintended, parasitic resistance or inductance in the ground connections (highlighted in red). The nodes A, B and C are all intended to be ground. But if current flows in parasitic ground impedances, these nodes will not be at the same potential. It is these parasitic ground impedances that can allow distorted ground currents to contaminate signals.

Walter’s specific question was, “where should you connect the bypass capacitor [the ground side].” It’s an important point. The currents flowing in op amp supply terminals (and therefore the bypass capacitors) may be distorted because they represent only half a sine wave. If distorted (or other interfering) current flows into a vulnerable ground node it can increase the distortion (or other errors) of the amplifier.

An interfering or distorted current flowing into node_A directly affects the ground reference of the input signal, summing in an error. Likewise, a ground current injected into node_B serves as a direct input to the amplifier stage (inverted, in the first circuit). Ground current flowing into node_C directly sums an error with the output voltage. This node may be less vulnerable because the error signal is not amplified by the circuit gain.

The bypass capacitor should be connected to node_G. Though there may be additional parasitic impedance on its way to other ground points, variation in voltage at node_G affects the critical nodes equally, so it does not inject an error or distortion. I’ve shown an op amp with a single power supply. The ground connection of the op amp (shown on top of the op amp) should also connect to Node_G. A dual (±) supply op amp circuit would have another bypass capacitor for the negative supply and it, too, should connect to node_G.

A solution is to create a circuit board that establishes a ground with the characteristics of node_G. The principle is simple—the circuit trace from the input ground terminal to the ground side of R1 should be a clear path with no connections to contaminating sources of current along the way (figure 2). This input ground trace can join a larger ground connection or ground plane where they meet. With some gain in this stage, output errors are less critical, but you still may want a separate trace to the output terminal connections.

The input ground connection should not connect to equipment chassis at an input connector. This would create an opportunity for other interfering ground noise (such as AC mains ground currents) from impressing current on the clean input ground trace.

A single blog cannot begin to cover all the issues relating to the art of grounding. Woops… did I call this an “art?” It’s science, not art! While, at times, may seem like black magic, Ohm’s law is always at work. Considering where ground currents flow and how they could affect the circuit is always a good start!

Thanks for reading. Comments welcome below,

Bruce

60 other interesting The Signal topics.

OpenMP - All aboard!

Debbie Greenstreet — Tue, 21 May 2013 16:50:45 GMT

With so many end products today relying on multicore DSPs for optimized solutions, I find it very encouraging to see that our multicore customers are leveraging the power of OpenMP as part of TI’s KeyStone software/tool suite. While some multicore engineers have learned to evolve single core programming through hand calculating and trial and error mapping of the software program, this approach is quite time consuming and will not scale well.

I am reminded of a time that some of our younger readers might find baffling, but the more experienced engineers may recall it well. Before Windows launched, avid PC users were well adept at DOS command line. The DOS command line memorized functions that enabled navigation around one’s own PC. When Windows was unveiled, some of the PC users rejected it - “Not me, I will not adopt. I will not give up direct access to the operating functions,” they said. Certainly, as PC applications continue to grow and performance increases, Windows offers a far more scalable means of managing the PC environment. This is why these PC users eventually learned to adopt the new operating system.

Similarly, in the multicore development environment, tools like OpenMP are necessary for time to market, productivity, product line scalability and optimizing product development costs. And, that is exactly what we at TI are witnessing. Our multicore customers who are using OpenMP with the TI KeyStone Code Composer Studio (CCS) tool set, including the recent compiler update that has performance enhancements for high data sets, see all of those benefits I mentioned above. So, to all of you multicore developers, are you on board?

To learn more about OpenMP, I invite you to check out our latest Ask the Expert video by Dr. Arnon Friedmann, where he answers why every multicore developer should be an OpenMP user. Also, if you are going to be attending the Multicore Developer’s Conference, be sure to check out the keynote by TI’s Andy Fritsch, Director of Foundational Tools, on Tuesday, May 21, at noon PT, where he will discuss how software RULES the world! Additionally, TI’s Alan Ward, Distinguished Member Technical Staff, will invite attendees to “Look where OpenCL™ is now!” on Wednesday, May 22. Alan will also be on a panel Wednesday evening to discuss Manycore or Anycore: Exposing the Limitations and Advantages of Manycore in Embedded Systems.

We hope to see you there!

Field Oriented Control Just Got WAY Simpler!

Dave (Wisconsin) Wilson — Tue, 21 May 2013 16:00:00 GMT

Dave Wilson, Motion Products Evangelist, Texas Instruments

At 6:31 a.m. on Feb. 26, if you were wearing your motor control goggles, you would have seen a bright flash in the skies over Texas. TI finally announced its long-awaited new sensorless Field Oriented Control (FOC) algorithm that it had been working on for the past couple of years. Called “TI InstaSPIN™-FOC,” this new technology promises to make FOC a lot easier to use while at the same time improving controller performance over a wider range of operating conditions. While the flash of this initial announcement is over, the motor control community will continue to feel the rumble from this big-bang for years to come!

I’m trying to think of how to communicate my excitement about this technology without sounding like a cheerleader. I’ve been in the motor control industry for 34 years. From fuzzy logic to the switched-reluctance craze of the late 90s, I have seen a lot of promising motor control technologies come and go. But in all that time, I can’t recall a technology announcement that had the potential to shake the motor control world like this one. But, enough flag waving. I will resist the urge to write using superlative phrases and grandiose keystrokes. Instead, let me bring it down to the bench level and explain why I think this announcement was so significant and why it will continue to rock the motor control world for years to come…

The first point I want to make is not related to the technology at all but how it is implemented. It is actually embedded within select C2000™ real-time control microcontrollers (MCUs) and is directly accessible as C-callable library routines. This exemplifies a growing business trend within TI to re-evaluate how we think about our products. At the last semiconductor company I worked for, I made the statement that “any processor company that still thinks its main product is silicon will be out of business within a decade.” Although my comment was not well received, I still believe it is true! In many cases, our silicon is just one component of our real product, which is our intellectual property. In my past life as a field applications engineer, having a superior piece of silicon almost always resulted in a sale. But today our customers demand more than just good silicon – they expect applications leadership and innovation. And THAT must be the prism through which we evaluate future products. I think it is safe to say that you can expect to see more innovations like this from TI in the future.

Second, TI InstaSPIN-FOC can make your job easier. A LOT easier! At the risk of overdramatizing my point, let’s just say that you can now go to your child’s music recital or sporting event after work instead of fighting with your motor control code until midnight. The research is done. The coding is done. The porting is done. All you have to do is call the functions you want. Whether you are an expert at FOC or even if this is your first motor control project, TI’s InstaSPIN-FOC can get you to the finish line much faster than trying to write the code yourself.

But even the best written code is worthless if it doesn’t perform. So let me highlight a few observations about what this technology can do for you. At the heart of TI InstaSPIN-FOC is a new sensorless engine that works like nothing I have ever seen before. You are probably aware that there are lots of different sensorless observers available today. In fact, TI has code examples of most of them already available on our website. But if you pop the hood on this engine you won’t see a sliding-mode observer. You won’t see a traditional back-EMF observer. And it doesn’t require you to inject any signals into the motor. It is something totally new. The result is a unified observer structure that works with almost any motor, over a speed range that spans over four orders of magnitude using today’s processor capabilities! We have already demonstrated practical examples of an eight-pole motor running down to five RPM without a shaft angle sensor, and a two-pole motor running up to 50,000 RPM. Unlike dual-mode observers that require extra bandwidth and mode switching between different speeds, the TI InstaSPIN-FOC observer requires no mode switching and no parameter adjustments regardless of motor speed.

We have named the observer “FAST,” which is an acronym derived from the four outputs of the observer: flux, angle, speed, and torque. Arguably, the angle estimate is the most important output since it drives the controller’s synchronous frame axis into alignment with the machine’s flux axis. It is the accuracy of this parameter that allows such elegant control over such a wide speed range. Another improvement that we have observed is how robustly the angle estimator behaves during transient conditions. While sliding mode observers we tested could easily be confused by sudden speed transients, FAST was able to track the same transients with ease.

Now that TI’s InstaSPIN-FOC has been released, don’t expect TI to just sit back and enjoy the fruits of its labor. We realize that this is a hugely competitive market, and we must continuously earn your business. To that end, we are already busy working on next-generation innovations that will enable this technology to perform even better in the future. There are many other features in TI’s InstaSPIN-FOC that I plan to address in future blogs. But for now, you can get more information about this new technology at our website.

Time will tell whether this technology really does change the motor control world. I am betting that it will. But for now, I just wanted to let you know that the sound you just heard is the collective cheer from motor control designers the world over as they just realized how easy and fun their next motor control project is going to be. :-)

Keep Those Motors Spinning,

www.ti.com/motorblog

TI and MIT collaborate on researching material that could be the next big thing that powers devices – including yours.

Around TI — Tue, 21 May 2013 13:00:00 GMT

Imagine a charger that powers your laptop – but it’s the size of a cell phone charger. It’s smaller and lighter, but still packs the same power punch. This is just one way that new material being researched today could save energy – and impact your life.

TI has been working with students and professors at the Massachusetts Institute of Technology (MIT) on the use of the material gallium nitride (GaN) in powering devices in homes and offices, to name a few areas of use. “Everyone hopes it’s the next new material for power devices,” says Dave Freeman, a TI Fellow and chief technologist for power supply solutions in analog. “Right now, it has some attractive features, but there are some challenges with it.”

Those challenges are what Freeman and other TIers have been working on, with the help of MIT students and professors. The material could help reduce the power loss– while reducing the total size of the circuit solution (it can run at a higher frequency, which would reduce the size of components). In other words, it could create high-power chargers that are small in size.

“It translates to an enormous amount of power saving,” says Saurav Bandyopadhyay, who did research on the material while pursuing his PhD at MIT. Bandyopadhyay started working on GaN studies during his second TI internship in the summer of 2011. The excitement behind the material had just sparked, and Bandyopadhyay spent time in TI’s research facility Kilby Labs, studying GaN’s potential in solid-state lighting.

His goal was to create a more efficient driver (or the device that powers LEDs) using a GaN transistor. “I was trying to come up with circuits that could do this efficiently,” Bandyopadhyay says. “I was working on the proof-of-concept to verify that it could be done. The goal was to make a product that people will actually use.”

At the end of the summer, he headed back to MIT to continue his research. “Everything I did at Kilby Labs was used later, and gave me an idea of what could and couldn’t be done,” he says. Working with Anantha Chandrakasan, head of MIT’s electrical engineering and computer science department and a pioneer on energy efficient circuits and systems, Bandyopadhyay successfully designed an efficient driver. It’s a final product that he applied to his thesis in order to earn his PhD (he just received his degree last week). He has published his study at International Solid-State Circuits Conference (ISSCC 2013), in San Francisco in February 2013.

“This was a new project and a new direction for me,” Bandyopadhyay says. “It was a really great learning experience. I was exposed to different devices and new concepts. It’s one thing to learn it in school, but when you have to build something in the lab, the concepts get instilled deeper. Book knowledge is one thing; implementing it is another.”

His project is, however, just the beginning -- many students and researchers are studying other ways GaN can be used (for instance, another MIT student Dina El-Damak spent time at TI researching integrated high voltage isolated power that can be used as part of the GaN ecosystem).

“I’m hoping to look at applications other than energy drivers,” says Bandyopadhyay, who just joined TI full-time. “The device has a lot to offer, and in order to get the full benefit, there are a lot of other things that need to be done.”

New book focuses on Battery Power

MattMcK — Tue, 21 May 2013 12:00:00 GMT

I sat down this week with Yevgen Barsukov and Jinrong Qian, two of TI’s leading battery technology experts to discuss the release of their new 240-page book, Battery Power Management for Portable Devices (by Artech House publishing -- available now on Amazon). The book provides comprehensive coverage of the latest battery management components and technology used in portable electronics, ranging from smartphones to ultrabooks and tablets and many other designs.

According to the authors, there is a growing need to educate battery pack makers and portable electronics manufacturers about the characteristics of batteries and battery chemistries.

“Over the last 10-12 years, we saw a large number of customers who tried to implement newer battery types and chemistries, from lead-acid to NiMH and NiCd and then higher-capacity lithium batteries,” said Qian, who is product line manager for TI’s battery chargers. It became really important to help clarify battery management concepts and outline the characteristics of different types of chemistries. Even though TI is the leading provider of power management integrated circuits, we have some of the best battery chemistry experts on staff.”

“We hope this book will be useful to a range of readers from engineering experts to students in related fields,” said Barsukov, IP development manager and chemist in the battery management systems group. “Our goal is to help them better understand power design techniques and battery characteristics – so that end consumers will ultimately experience portable electronics with long battery life, faster charging and safer batteries.”

Battery Power Management for Portable Devices discusses how to use new innovative charging circuits for faster and cooler charging; how to design with battery gauge technology that provide the longest possible run-time, while ensuring data protection; and utilize safety circuits that provide multiple independent levels of battery protection. The book provides real-world perspective of battery management systems, and covers:

Battery Chemistry Fundamentals and Characteristics
Battery Charger Techniques
Battery Safety and Protection
Cell-Balancing Techniques
Battery Fuel Gauging (state-of-charge and remaining run-time indication)
System Battery Power Management Solutions

The book already received a couple of notable reviews from other industry experts.

“This book provides valuable insights into why batteries behave the way they do so that you can understand how to use them in an optimal fashion. Recognized as industry experts, Jinrong and Yevgen have compiled a comprehensive set of information using their extensive experience in practical battery management. This book will certainly be perched on my desk, and I expect to refer to it often.” – Andy Keates, battery technologist at Intel Corporation. (As referenced in the Foreword of the book).

David Andrea, author of “Battery Management Systems for Large Lithium-Ion Battery Packs,” reviewed the book on his blog.

I hope my colleagues find great success with their first book!

MSP430@Maker Faire

William Cooper — Tue, 21 May 2013 01:44:50 GMT

We know that not everyone could make it out to Maker Faire, so check out our Make the Switch blog for updates from this past Saturday. The TI booth was hopping and we even had some of our own resident authors out for the event!

Want more? Read up on how you can create real solutions (wireless light switch displayed at the event) using Energia and the MSP430 LaunchPad.

A look back: Two years of Multicore Mix

Lauren Reed1 — Mon, 20 May 2013 16:09:21 GMT

A big thank you to everyone who participated in our contest last week! We loved hearing about how our blog posts have inspired you. Congratulations to David Hoelscher for submitting the winning response: “I found the three-part series about Multicore Navigator Tips 'n Tricks very helpful in understanding the various ways it can be used. In particular, using the Queue Manager for Notification purposes as a means to avoid moving data and improve efficiency was very appealing.”

We have had a great two years on the Multicore Mix. We thought it would be an appropriate time to take a look back at a few of our top blog posts and the accompanying comments over the years.

Do we really need ‘Transactional Memory’? (By one and zero) explained what Transactional Memory is, how it works and asked the question do we need it?
Anybody got tools? (By Tom Flanagan) helped familiarize our Multicore Mix readers with the next steps after selecting a snappy new multicore device!
Happy Anniversary, Multicore Mix! Celebrate by entering a MONTH of contests! Everyone loves a contest! Last year, we celebrated our first anniversary by giving away a prize bag to a fan of the Multicore Mix. We chose our favorite answer from readers who wrote why they were a Multicore Mix fan in 50 words or less.
Share your love of MULTICORE – and win BIG! This contest was all about our LOVE for the readers of the Multicore Mix. In celebration of Valentine’s Day, we asked readers to tell us why they loved multicore for a chance to win a $100 Visa gift card and a box of chocolates!
The answer is “42.” What was the question? (By one and zero) discussed programming language and how to know which is best suited for multicore architecture.

If you didn’t enter the contest last week, don’t worry! Since it’s our SECOND anniversary here at the Multicore Mix, we are going to have TWO contests this month. This time we want to know what you would like to see covered in our third year. Do you want to see more about tradeshows, design tips, tutorials or even trends in vertical markets? We want to know!

To enter this contest, comment on this post to let us know what you want to see in the next year, and our bloggers will select their favorite suggestion based on which one they feel is most relevant and interesting to our multicore audience. You have until midnight CST on Sunday, May 26, to enter! The winning comment will get a $100 Visa gift card and a multicore T-shirt. The winner will be announced on Tuesday, May 28.

CONTEST DETAILS: This contest is open to all residents of the United States. TI employees and their family members cannot enter the contest. Prizes will be shipped via Fedex Ground and cannot be shipped to P.O. Box addresses. Entries will be judged based on what our Multicore Mix bloggers consider to be the best comment on what they want to see in the Multicore Mix this next year. The selected winner must respond to the email notification within 72 hours or they will forfeit the $100 Visa gift card and multicore T-shirt. If the selected winner does not respond within 72 hours, an alternate winner will be chosen based on originality and content of response by Multicore Mix bloggers.

Call for Innovation – Part II

Ravikumar C.P. — Mon, 20 May 2013 09:42:09 GMT

Call for Innovation – Part II

What can you look forward to, if you are taking part in Texas Instruments Innovation Challenge: India Analog Design Contest

C.P. Ravikumar, Texas Instruments

Listen to what the winners of last year’s contest have to say about Texas Instruments Innovation Challenge: India Analog Design Contest!

"This is taking it too far! Even the winners' stand is analog!"

The cake and the icing

I remember the evening of April 5, 2013 distinctly. About 700 people had gathered in the “Silicon Hall” of NIMHANS Convention Center, Bangalore. The atmosphere was charged with excitement. Twenty three teams who had been shortlisted for the second round of the “TI India Analog Design Contest” waited with bated breath for the award announcements. Foot-tapping music played as student teams and mentors climbed on to the stage to receive the awards.

I wish to reiterate what I said at the beginning of this award ceremony in my capacity of the host of the event. Every student who took part in the contest and completed the project is a winner. The true reward of participating in the contest is the learning that the students derived. The awards are only the icing on the cake.

I have already disclosed who the winners of the contest were in an earlier blog post (see [1]). The purpose of this post is different. We had a chance to interact with the winners of the contest when they visited TI’s Bangalore campus and made seminar presentations about their projects to an invited audience. We used the opportunity and asked them to describe their overall contest experience. I will share their secrets with you, if you promise me that you will share it with at least five others.

Fruitful Learning Experience

“It was a fruitful learning experience … made us improve our intellectual and engineering skills.” This is how Dinesh P, an undergraduate student in the Department of Electronics and Communication Engineering, National Institute of Technology, Tiruchirapally, sums up the experience of his team. Incidentally, his team won the top prize in the contest.

What was the challenge their team faced? “Designing and debugging the hardware system was the challenging part,” says Dinesh. ”But we learnt a great deal. While we picked up a lot of knowledge in the application domain (solar inverter), there was much to learn about the ICs we used - power electronics ICs, op-amps, voltage regulators.”

His teammate Bhaskar adds to this list. “We learnt to design high power printed circuit boards. We also became adept in using the TI MSP430 series of microcontrollers.

“Working as a team was great fun! And of course, winning the competition was the sweetest experience!” Our project was an exercise in system design. We had to address many concerns, such as power consumption, self sustainability, reliability etc. Now we are planning to patent our idea.”

Their message to next year’s contest aspirants is “Give in your best effort folks! It will definitely be one of the best learning experiences in college.”

Hello, Real World

“Through this contest we experienced what real world electronics system design is!” says Varun Reddy of NIT Surathkal, whose team shared the top award with NIT Trichy. “It gave me a reason to tinker around and experiment with things I normally wouldn't have done.”

“In our project, we touched upon all the aspects of system design starting from hardware aspects (PCB design and sensor design) to software aspects (Linux and C coding.) We also had to think of system integration which involved putting all of these individual components together into a single usable product. I feel final system integration, making every part work together after individual testing was most challenging.

“The technical learnings that we obtained through this project include: PCB design, RTOS coding, various communication protocols such as Zigbee and WiFi, and to some extent, Linux coding. In the initial stages of the contest, TI’s e2e community was very helpful when we needed information on how to get started with the development kits provided by TI. Our faculty mentor was very helpful and provided lot of helpful guidelines on how to make our project better.”

“I am planning to apply for higher studies abroad, and the contest has provided me with exactly the kind of experience to succeed in the chosen field of my study. Winning the contest will definitely help in the admission process, as it is a very important achievement and I can use it to showcase technical capability.”

Felt like Entrepreneurs

“The contest was the best platform to pick up skills in electronic system design,” says Raghav A. His team from BNMIT, Bangalore, won the First Runner-up Award. “Students who are interested in product design seldom get this kind of unique opportunity. I have participated in other contests also, but the kind of support TI provides by giving components, offering tutorials etc. is phenomenal”

“We enjoyed demonstrating our project at TI India Educators Conference! We felt like entrepreneurs!” added Raghav. His team mate Shashanka D agrees. “We enjoyed explaining their project to educators and industry professionals who visited our booth at TI India Educators’ Conference.”

Shashank believes he learnt a great deal during the contest. “I learned a lot about analog ICs and microcontrollers from TI, MSP430. I understood the differences between different IC packages and their importance. I also learnt a PCB design tool and the PCB manufacturing process, and autocad for designing the case for our safety lock.”

“Getting all the components from TI was great encouragement for us. We also appreciate the sharing of project videos and conference pictures through social media and blogs. It was a motivating factor for us.”

“We used C2000 microcontroller from TI - Piccolo F28027 in our project. Learning this controller and interfacing it with MATLAB was a great experience,” said Harshitha N of BMS College of Engineering.

Soft Skills

“Apart from technical skills, the contest helped us in learning lots of non-technical skills such as team management, coordinating with team members, personality development and working under deadlines,” said Prem Sagar, a student member of the team from Netaji Subhas Institute of Technology, New Delhi.

“I have participated in many contests which are generally open-ended. But the TI contest has clear guidelines & directions, which were very helpful. A unique feature of the contest was project demonstration through video which tested our creative skills. We were thrilled to win the best video award for our video demonstration” says Hitesh Mittal from Chitkara University, Punjab. His team mate Jai Aditya said “We are planning to productize our project prototype and in this regard we are talking to our college for support.”

“The contest exposed us to a wide variety of technologies that has inspired us to pursue higher studies,” said Kishore P of NIT Tiruchirapally. He advice to the next year’s contestants is, “Manage time. Make sure you carefully select a project that you should be able to finish in given time period while managing your academics.”

Innovation Challenge

The purpose of writing this blog post is to encourage students to take part in the next year’s contest, which we have renamed “Texas Instruments Innovation Challenge: India Analog Design Contest.” I hope the positive experiences of the participants who took part in previous contests will motivate more students to take the plunge! I know many of you are completing your semester now and looking forward to a summer break. It would be useful to form your team now and start thinking about your project proposal, which is due by August 15. In the next part of this blog series, I intend to write about selecting projects.

After reading the first part [2] of this blog series, a few students wrote to me. Some of them incorrectly think that the contest is about making new inventions. I want to reiterate that our contest challenges students to “innovate.” Read the article [3] to appreciate the difference between innovation and invention. You may also benefit from reading the interview at [4] and the article available in [5]. You will benefit from the “Guidelines” document we have posted at [6]. The contest website anchored at [7] is also a great resource from where you can get information about the colleges which were shortlisted in the previous years, the links for their video demonstrations, etc. Happy reading!

References

[1] C.P. Ravikumar. Innovation Premier League!

[2] C.P. Ravikumar. Call for Innovation – Part I - Top Ten Reasons for participating in Texas Instruments Innovation Challenge: India Analog Design Contest 2014 http://e2e.ti.com/blogs_/b/designproject/archive/2013/05/16/call-for-innovation-part-i.aspx

[3] English Wikipedia. Innovation. http://en.wikipedia.org/wiki/Innovation

[4] C.P. Ravikumar’s interview published in Electronics Maker, May 2013. http://www.uniti.in/images/interview.pdf

[5] System-level Design: Nurturing College Students to Innovate through TI India Analog Design Contest http://www.uniti.in/images/system-level-design.pdf

[6] Guidelines Document for Texas Instruments Innovation Challenge: India Analog Design Contest. http://www.uniti.in/adc/texas-instruments-innovation-challenge-india-analog-design-contest-2014

[7] Website for Texas Instruments Innovation Challenge: India Analog Design Contest. www.uniti.in/adc

RS-485 - Who says you can't teach an old dog new tricks?

Neel Seshan — Fri, 17 May 2013 20:37:00 GMT

Would you agree that RS-485 has turned out to be one of the most versatile communication standards when it comes to industrial applications? It’s very reliable for long distance communication and very popular. In all the years that the RS-485 standard has been around, RS-485 transceivers have undergone a lot of changes. Just like we crave more "apps" on our phones, RS-485 users want more features in the transceivers making it safer and robust.

With safety and protection in the forefront for industrial applications, transceivers today have a bunch of safety features packed into the same package. If you fear the common-mode voltage in your system is going to violate the standard (-7 to 12V), then simply choose one that has two times wider common mode range, such as the SN65HVDHVD20. By the way, we call these SUPER-485 devices because they are the true super-stars when it comes to industrial applications/harsh environments where there is likelihood of ground movement.

For cases when there is a possibility of over-voltage faults due to accidental shorting of wires to power supplies or mis-wiring, one could use transceivers, such as the SN65HVD1780, which are high-voltage fault protected. As long as the voltage on the bus lines in not greater than 70V, the device will survive. Once the fault is corrected, the system will work as expected.

Lastly, if there is clutter on the board surrounding the transceivers such as ESD diodes or transient voltage suppression (TVS) diodes, why not clean them up with the SN65HVD72 family or the SN65LBC184 devices? These devices, especially the SN65LBC184, will ensure that a lightning strike does not damage your transceiver. Yeah, it's that robust; we call it our SUPER-DUPER485.

Oh!! Did I mention each of these transceivers is backward compatible to the basic RS-485 transceiver without any frills? So upgrading your old solution should be as easy as hitting the easy button at Staples. Well, maybe not, but as easy as un-soldering the old device and soldering in one of these super-stars. Then watch your old RS-485 system breathe a new robust life.

Make our day - Meet our Makers at Maker Faire!

Susan Barr — Fri, 17 May 2013 15:53:00 GMT

Quirky robots, fire-breathing metal dragons, and a parade of amazing prototypes can mean only one thing - Maker Faire is finally here! Maker Faire is a family-friendly festival filled with a mix of innovative and creative designs and is a place where Makers of all kind can gather together to celebrate their creations. This year at the San Francisco Bay Area Maker Faire, we will be demonstrating MCU LaunchPad-based projects, holding a few giveaways and sharing some exciting news for the Maker community! Come by and see us in booth 504 – it will ‘Make’ our day. Want a sneak peek of the show? Read below for more details!

We’ll have a few things to share at the TI booth, including:

Energia – Simple code editor for the LaunchPad

We are excited to share Energia with the maker community at Maker Faire! Energia is an open-sourced, community-developed integrated development environment (IDE) developed with MCU LaunchPad and BoosterPack designers in mind. Energia breaks down and simplifies coding, making development easier for engineers, hobbyists, and students to start creating code for our LaunchPad ecosystem. Energia is also supported by a large, active, and friendly online community. Users can share ideas, ask and answer questions, and get integrated into one of the best maker communities at www.43oh.com. Robert Wessels, the founder of Energia, will be at our booth to answer questions and demonstrate this new IDE at Maker Faire. Learn more about Energia by stopping by our booth or by visiting www.energia.nu

Energia Library for the CC110L RF wireless BoosterPack

Our third party partners from Anaren will also be at the TI booth to announce a new Energia library for the 430BOOST-CC110L RF Air BoosterPack! This kit includes 2x RF BoosterPacks for just $19! Wireless development has never been more accessible when you pair affordable hardware with this new easy-to-use Energia library. Learn more about the Anaren CC110L BoosterPack here!

Modkit – Graphical programming on the LaunchPad

A third party graphical user interface (GUI) based tool for programming that utilizes drag and drop code blocks to make designing on your LaunchPad a breeze. Having Modkit running on the LaunchPad will help anyone interested in designing with TI MCUs the ability to start blinking LEDs and programming their LaunchPads' in seconds. Stop by our booth to meet the Modkit founders and experience Modkit for LaunchPad! Learn more about Modkit in our booth or online via blog.modk.it

Meet our friends from www.43oh.com

But wait, there’s more! Just when you thought we were finished, Gerard Sequeira, the founder of the 43Oh community, will be on hand to answer questions about the 43Oh community and showcase some neat community-developed BoosterPacks and demos.

BeagleBone Black and the BeagleStache

What Maker Faire is complete without BeagleBone Black open-source Linux computers? The Maker Shed booth will have 200 of these boards, based on our Sitara™ AM335x ARM®\ Cortex™-A8 processor, available for purchase. Our own Jason Kridner will also be at the show with his BeagleStache cam, so track him down if you want to electronically “grow” an irresistible mustache and show it to your friends on Twitter. These BeagleStaches look great on men, women and babies alike!

Of course what would a show be without awesome giveaways?! We will have buttons, t-shirts, carrier bags, copies of Getting Started with MSP430 LaunchPads and even a LaunchPad or two as giveaways.

As always, stay connected to all things ‘MAKE’ through Twitter (@TXInstruments) , TI Facebook page and MCU Facebook page to get all the current Maker Faire action at your fingertips.

Unable to make it to Maker Faire? Participate online with our #NameThatMaker contest – look for hints describing famous Makers on our social media channels (Twitter, Facebook and Google+ ) for the chance to win one of each MCU LaunchPad in the lineup or a BeagleBone Black! See the full list of rules and regulations for this contest here.

Getting to TI on two wheels

Around TI — Fri, 17 May 2013 13:00:00 GMT

TI was recently included as one of 63 new Bicycle Friendly Businesses (BFB) from across the country from The League of American Bicyclists. And with spring in the air and May being Bike to Work month, it’s the ideal time to hit the pavement on two wheels.

"Texas Instruments sees great value in supporting alternative commuting solutions for employees," said David Thomas, vice president and manager of Worldwide Facilities at TI.

"We've invested resources to build bike paths that connect to local trails, added bike racks, repair stations and onsite showers, and created social networks that support TI bike commuters. We want to make it easy for our existing bike commuters to get to work safely and to encourage more employees to try biking to work.”

To read more about TI making the Bicycle Friendly Business list, visit our Corporate Citizenship News site.

#NameThatMaker Social Media Giveaway

Susan Barr — Thu, 16 May 2013 18:10:00 GMT

Our team is excited to participate in Maker Faire and we’d like to share our excitement with you! From May 17 – 19, we are hosting the #NameThatMaker contest on our Google+, Twitter and Facebook pages. Stay tuned for hints appearing on these channels referencing an influencial Maker. Respond back with the name of the Maker we’re describing and you could win an MCU LaunchPad ecosystem or a BeagleBone Black!

See below for official contest rules.

Good luck and happy Making!

MAKER FAIRE: #NAMEThatMaker GiveAWAY CONTEST RULES

For purposes of these Rules, “TI” shall mean Texas Instruments Incorporated and its subsidiaries.

1. To be eligible to compete, each entrant must read and agree to abide by the Contest rules.

2. Each entrant must correctly respond to the hint with a comment on Facebook, a tweet with the #NameThatMaker hashtag on Twitter, or a comment with #NameThatMaker on Google+.

3. Entries must be in English.

4. The Contest begins May 17, 2013 at 12:00 p.m. (CDT) and ends May 19, 2013 at 10:00 p.m. (CDT). No submissions submitted after May 19 at 10:00 p.m. (CDT) will be considered. The award recipients will be contacted before 6:00 p.m. (CDT) on May 20, 2013 and will have until 6:00 p.m. (CDT) on May 24, 2013 to claim their prize by messaging TI his/her address. TI reserves the right to cancel this Contest phase before the end date at its sole discretion, and decline to award prizes if there are no eligible entrants.

5. Only one entry per person is allowed on each TI social media platform for each hint given during the Contest.

6. Odds of winning are determined by the total number of eligible entries received.

7. TI reserves the right, at its sole discretion, to disqualify anyone found to have tampered with the Contest.

8. The contest is offered and participation is limited to only RESIDENTS OF the united states, Canada and MexicO.

9. To be eligible, entrants must be eighteen (18) year of age or older.

10. THERE IS NO ENTRY FEE.

11. ENTRANTS DO NOT RECEIVE BY WAY OF OR UNDER THE CONTEST ANY INTELLECTUAL PROPERTY RIGHTS IN ANY COPYRIGHTS, PATENTS, TRADEMARKS, TRADE NAMES, TECHNOLOGY, TRADE SECRETS, OR KNOW-HOW OF TEXAS INSTRUMENTS OR ANY THIRD PARTY.

12. Entrants must agree to these terms and conditions to be eligible to participate in this Contest. Entries must be submitted by the deadline to be considered. Entrants will not be allowed to change or supplement their submissions once they have been submitted.

13. All entrants agree to follow and abide by the judging criteria.

14. All entrants warrant and represent that their entry is entirely original and that entrant is the owner of said entry. This representation is a requirement of participation in the Contest. By participating in the contest, all entrants represent and that there is no third party of any kind, whether an academic institution, commercial company, individual, or governmental legal entity which has any proprietary or other interest in, claims or rights to, any intellectual property rights, including trade secret, “know-how,” copyright, patent, trademark or trade name, in any material submitted under the Contest.

15. All entrants agree, represent and guarantee that there are no obligations of any nature, legal or otherwise, which would prohibit, restrict, or interfere with their participation in the Contest. All entrants agree to obtain any necessary clearance or approval from any necessary third party participation in all Contest activities and any such approvals, which are required as a condition of participation.

16. No confidential relationship is established between TI and the entrant as a result of entering this Contest. None of the content submitted by the entrants will be treated by TI as trade secrets, confidential information, or as protected data under any obligation.

17. Taxes (United States federal, state and local) and other obligations are solely the responsibility of the winners. Prizes may be subject to reporting for tax and other purposes. Winners agree to supply TI with any information necessary for tax reporting purposes and to cooperate in fulfilling all applicable legal requirements.

18. The entrant that is chosen for consideration for any award, as a condition of award, may be required to submit further information concerning employment and residence. Also, as a condition of award, the entrant may be required to sign a liability/publicity release.

19. The non-exclusive license to TI of intellectual property rights, as described herein, is free of charge and without remuneration of any kind. All entrants agree that the opportunity to compete for prizes and receive publicity represents full and adequate consideration for license of these rights by all entrants. Prizes do not represent fixed-sum monetary remuneration of the licensing of intellectual property.

20. All entrants grant to TI the right to publicize their names, likeness, any information provided on their Facebook profile, their Google+ profile, or their Twitter handle in whatever manner without reservation or compensation. Entrants further agree to execute, at TI’s request, a publicity release related to TI’s use of an entrant’s name, likeness or information.

21. Entrants will not be reimbursed for any costs incurred or for efforts expended in connection with their participation in the Contest. Such costs are the responsibility of the participants.

22. NO PURCHASE IS NECESSARY.

23. Decisions by the Contest judges are final. TI reserves the right to refrain from awarding any prize if there are no or minimal qualified entries.

24. PRIZES: Three (3) winners of the first contest each day will receive C2000™ Piccolo LaunchPads valued at $17.05, EK-LM4F120XL Stellaris LM4F120 LaunchPads valued at $12.99, and MSP430 LaunchPad Value Line Development Kits valued at $9.99. Three (3) winners of the second contest each day will receive BeagleBone Black boards valued at $45 USD each. Total approximate value of all prizes: $255.

25. In the event of unavailability of any of the stated prizes, TI reserves the right to substitute items of equal or greater value.

26. If a winner cannot be reached by 6:00 p.m. (CDT) on May 24, 2013, TI reserve the right to deem the prize forfeited.

27. Employees and agents of TI and such individual’s immediate family (including spouse, children, parents, siblings, grandparents, grandchildren, step-children, step-parents and in-laws) and members of the same household are prohibited from entering this Contest.

28. THE CONTEST SHALL BE CONSIDERED VOID WHERE, AND TO THE EXTENT, PROHIBITED BY LAW.

29. TI reserves the right to use information regarding contestants for future mailings subject to applicable laws and regulations and privacy policies. TI’s privacy policy can be found at www.ti.com/home_f_privacy.

30. Subject to verification of eligibility and compliance with all Contest rules, one person who correctly responds to each hint will be randomly award a Prize during the contest.

31. No entries will be returned to participants, regardless of whether they are accepted. The winners’ names will be published on TI’s websites and media outlets.

32. If there is a dispute regarding the identity of the entrant, TI reserves the right to deem the account holder of the e-mail address as the entrant.

33. THE CONTEST AND ITS RULES AND CONDITIONS SHALL BE GOVERNED BY THE LAWS OF THE STATE OF TEXAS AND ANY DISPUTE ARISING OUT OF THIS CONTEST SHALL BE BROUGHT IN, AND YOU HEREBY CONSENT TO EXCLUSIVE JURISDICTION AND VENUE IN, THE FEDERAL DISTRICT COURTS SITTING IN DALLAS COUNTY, TEXAS.

34. If any aspect of the Contest or any rule or condition be found by a court of competent jurisdiction to be invalid, illegal or void, participants agree to allow TI to change such provision and, upon notice, to make it valid. Also, in such case, the remaining Contest provisions shall remain in full force and effect and the Contest shall proceed accordingly.

35. Winners will be notified by TI by 6:00 p.m. (CDT) on May 20, 2013. The prizes will be shipped to the winners no later than 6:00 p.m. (CDT) on July 26, 2013.

36. By entering this Contest, each entrant agrees to release and hold TI harmless from and against any losses, damages, rights, claims and actions of any kind arising from (i) an exclusion or disqualification of an entrant pursuant to these Rules; (ii) late, lost, misdirected, or unsuccessful efforts to notify winners of any prize; (iii) forfeiture of a prize and the selection of an alternate winner; (iv) late, lost, delayed, damaged, misdirected, incomplete, illegible or unintelligible entries; (v) telephone, electronic, hardware or software program, network, Internet, or computer malfunctions, failures or difficulties of any kind; (iii) failed, incomplete, garbled or delayed computer transmissions; (iv) any condition caused by events beyond TI’s control that may cause the Contest to be disrupted or corrupted; (v) any injuries, losses or damages of any kind relating to a contest prize, or acceptance, possession or use of the prize, or from participation in this Contest.

37. TI reserves the right to cancel, terminate, modify or suspend this Contest if it becomes corrupted or if for any reason the Internet portion of the Contest is not capable of running as planned, including infections by computer virus, bugs, tampering, unauthorized intervention, fraud, technical failures or any other causes beyond the control of TI, which corrupt or affect the administration, security, fairness, integrity or proper conduct of this Contest.

38. A list of the winners will be available after May 24, 2013. For a list of the winners, send a self-addressed, stamped envelope to:

Tara Stratton

GolinHarris

13155 Noel Road

Suite 750

Dallas, TX 75240

39. Sponsor:

Texas Instruments Incorporated
12500 TI Boulevard
Dallas, Texas 75243

Dave's Powertrip: Big Numbers, Big Confusion

Dave Freeman — Thu, 16 May 2013 17:26:00 GMT

It seems that big numbers carry with them big confusion. Big numbers from the age of the universe to the national debt can lead to interesting conversations at the lunch table. The magnitude of such numbers draws our attention, and the engineer in us leads us to make some use of these numbers. For example, the recently updated estimated age of the universe is 13.82 billion years, an increase of about a million years.¹ It is interesting that the reported value doesn’t even have 1 million as a significant digit in the reported age. The real point of the change is that the universe is expanding slower than originally thought.

In my last post, I talked about the power drain on my cell phone when comparing 3G to 4G networks. In April of this year, Centre for Energy-Efficient Telecommunications (CEET) published a report titled, “The Power of Wireless Cloud.”² This is an excellent report and quite easy reading. The report makes several interesting points and predictions. For example, the wireless cloud consumes about 9.2 TWh in 2012, and is expected to grow by 460% to 43 TWh by 2015. Another point is that only about 9% of the wireless cloud energy is consumed by data centers. With all the focus on data center energy efficiency, I would have thought that data centers are a far bigger energy hog.

An earlier report by Dr. Jonathan Koomey states that data centers consume between 1.1 to 1.5 percent of global electricity.³ This is a very large number. The World Bank estimates that the global production of electricity is about 21.49e12 kWh or 21,490 TWh.⁴ Even 1.1 percent is about 236 TWh. This is considerably more than estimated by CEET. So where is the confusion?

Figure 1. From smart phones to the cloud and the energy need.⁵

Alcatel-Lucent reported on the power and energy of worldwide base stations and their connected systems.⁵ This analysis shows that the big energy appetite comes from wireless base stations. Figure 1 shows that the estimated energy consumed annually by wireless base stations is about 60 TWh, while the server and related services consumed is about 14 TWh. This ratio is not quite what was reported by CEET. The Alcatel-Lucent report also addressed the power amplifier’s (PA) power efficiency, showing a range of efficiencies from 6 to 40%, depending on the output power.

Filter for thought

Soufiane Bendaoud — Thu, 16 May 2013 14:45:00 GMT

Have you ever wondered how engineers designed active filters before the birth of software? They were able to do it using nomographs - but before we talk about what these are, let’s refresh our memory a little bit on active filters.

Magnitude is the amplitude of the output. Phase is the angle of the output. Every pole adds -90° at high frequencies. Theoretically, a fourth order filter would phase shift through 360°, though the magnitude would be very small.

Group delay, on the other hand, is the derivative of phase with respect to frequency. It’s a measure of the time delay (filter’s time) in frequency. A filter with a flat group delay means that the output signals come out with the same relative phase as the input signals. In essence, everything is delayed by the same amount.

Before you decide on your filter design consider the tradeoffs between the various implementations and types. Let’s review a few important ones:

Narrower transition regions require higher filter order filters. That is, you’ll need a higher component count - active and passive. If you can tolerate more ripple in the passband, you can get a smaller transition region for the desired attenuation. However, a monotonic passband gives you a smoother phase response which yields a constant group delay in the passband, important in multi frequency communication.

Now that we touched on some of the tradeoffs, let’s take a look at some of the most common types of active filters.

The Butterworth has a monotonic passband and stopband. It’s optimal with respect to passband ripple, also known as maximally flat but has a wide transition region. It’s often chosen for anti aliasing.
The Chebyshev has an equal amount of ripple in the passband and a monotonic stopband, providing a fast transition region.
The Elliptic, sometimes referred to as a Cauer filter, has equal-ripple in both the passband and the stopband and gives you the fastest transition band of any filter. It does, however, have a long tail of settling time and requires a more complex implementation including poles and zeros in the transfer function.
The Bessel, also known as Thomson filter, offers the most constant group delay in the passband. It’s optimal with respect to group delay and is also called a linear phase filter, not to be confused with zero phase. The Bessel has a monotonic passband and stopband but has a wide transition region.
The Inverse Chebyshev gives you a monotonic passband and equal ripple in stopband, with the same transition region as the Chebyshev .

Take a look at figure 1 below to see the different filter bands described above.

Figure 1. Representation of different filter bands

So now what about those nomographs?

Suppose you want to design a low pass filter, assuming an active filter with -3dB at 300kHz and -60dB at 1.2MHz. Once you’ve decided which filter type you’re going to use, you’ll need to determine the minimum filter order.

Suppose you want to design an anti-aliasing low pass filter where your goal is to minimize ripple. You’ll need to look at the Butterworth nomograph and follow these steps:

Determine Ω= Ω_S/Ω_P
Extend a line to connect between M_P and M_S
Draw a horizontal line across graph to intersect Ω
The higher number represents the minimum filter order

In this example, you’ll need a fifth order.

If you plug the same numbers into FilterPro, you get the same answer. See the below figure.

Suggesting a “good” op amp for an active filter is not a trivial task and depends greatly on the implementation as well as the application. If you have a low voltage design and are in need of good settling time and low ripple the OPA320 is a good candidate. If your design uses higher voltages and requires good linearity consider the LMP8671 or OPA211.

For more info on how to ensure measurement set-up is properly calibrated and matched to avoid measurement errors due to ripples check out Habeeb Ur Rahman Mohammed’s “How to understand ripples in RF perfomances” Engineer It video.

Welcoming TI's summer interns. Wise words from TI's Dave Freeman.

Around TI — Thu, 16 May 2013 13:00:00 GMT

“We have quite a few summer interns come into our lab and they certainly bring a new level of energy with them. The students find that not only are they assigned to engaging and interesting projects but they are surrounded by many different and attractive technology developments. This gives them opportunities to collaborate outside their day to day work. A common comment at the end of the summer term is how fast their time in the lab has gone by. I think this is what happens when you are very focused on technology development and the future while having fun.” - Dave Freeman, Texas Instruments Fellow and Chief Technologist for Power Supply Solutions in the Power Management business unit

TI extends a warm welcome to its summer interns! And to check out more from Dave Freeman and his work with students, visit Dave's Powertrip series on the Power House blog.

Call for Innovation! - Part I

Ravikumar C.P. — Thu, 16 May 2013 11:20:00 GMT

Call for Innovation!

Part I - Top Ten Reasons for participating in Texas Instruments Innovation Challenge: India Analog Design Contest 2014

C.P. Ravikumar, Texas Instruments

The student walked towards the department's notice board, where a small crowd had gathered. They were peering at a new colorful poster about "Texas Instruments Innovation Challenge: India Analog Design Contest." There was a palpable excitement in the air.

"Should I enroll in this contest too?" the student wondered. Several questions raced through the student's mind. What does it mean to "innovate?" What skills are needed to take to participate in the contest? Am I expected to invent something? Will I be able to manage the contest-related work along with my academic load? How do I select team mates? What project should we select? What components will I need? Who will guide me through this process?

Thousands of Indian students may be going through a similar experience as I write this. We have been organizing the “Analog Design Contest” in India for four years in a row, and we are only too familiar with the frequently asked questions. We decided to help the students a little more this year, and that is the genesis of this blog series.

We decided to begin at the very beginning, a very good place to begin: Motivation! Why should you take part in Texas Instruments Innovation Challenge? Each year, we ask several participants, including winners of the contest, what prompted them to take part in our contest. Sagar has helped me summarize their answers in the table below. If you are that student who stopped by the notice board, wondering if the design contest is your cup of TI, the answer is yes! After you read the "Ten Reasons," I will recommend that you read the guidelines document which we have put together! (This document can be accessed from http://www.uniti.in/adc/texas-instruments-innovation-challenge-india-analog-design-contest-2014).

So here they are, ten practical reasons for which our past participants gave us a for our Analog Design Contest.

	I don’t have to pay any enrollment fee! TI provides to my team semiconductor components (ICs and hardware kits) free of cost!
	The knowledge and experience of the contest will boost my resume – whether I am interested in a job or in higher studies!
	TI provides a comprehensive “Semiconductor Tools Selection Guide” … this will make my job of selecting right TI components for my project a lot easier!
	With about six months for the project, I and my team can do some serious innovation! I can balance my coursework with contest-related work!
	I, my team members and my college get recognized by TI in various forums like contest website, social media etc.
	TI will provide me opportunity to showcase/demonstrate my project in a summit that will be attended by industry professionals, educators and students of Indian engineering colleges across India. This will be a great learning experience for me!
	After the contest is over, TI will allow me to patent my project idea, present it as my final year project, and even publish it in external forums.
	I can improve my non-technical skills like writing a good project report; making a good project video, working in a team, working under deadlines, time management, communication skills etc .
	It will be a lot of fun to work in a team! I am allowed to pick team mates from other departments! A team can have a mix of UG and PG students!
	There are also loads of tangible benefits! 1. Participation certificates for all participants! 2. Cash Prizes for teams shortlisted in First Phase! 3. Opportunity to do internship in TI 4. Cash prizes for winners in Final Phase - Top Prize of $10,000, First Runner-up Prize of $5,000 and Second Runner-up prize of $2,000 5. Chance to win other prizes!

I plan to cover several other aspects of participating in the Texas Instruments Innovation Challenge in the next part of the blog series. Meanwhile, I encourage you to start forming your team and start thinking about writing a proposal!

Teaching Your PI Controller to Behave (Part X)

Dave (Wisconsin) Wilson — Wed, 15 May 2013 22:13:00 GMT

Dave Wilson, Motion Products Evangelist, Texas Instruments

Throughout this series we have discussed a practical and efficient way to tune the PI controllers in a cascaded velocity loop by simply choosing a factor that determines the desired damping of the system. From this information, plus a rudimentary knowledge of some of the motor and load parameters, the PI coefficients for the velocity loop and the inner current loops can be calculated. We developed this technique by first ignoring certain aspects of the control loop, such as the pole of the current controller. But in blog 6 we reintroduced the current controller’s pole back into the discussion, and evaluated its impact on system performance.

Today, let’s look at the other end of the frequency spectrum. At low frequencies, viscous damping may affect your velocity loop response times by changing the phase margin at the unity-gain frequency. When viscous damping is present, it siphons off part of the motor’s torque to do work to move fluid. Since viscous torque is directly proportional to the speed of the load, we can rewrite the load’s transfer function to be:

Equ. 1

where k_v is the viscous damping factor

As you can see from Equ. 1, adding the viscous damping term moves the pole that was at s = 0 to s = k_v/J. Figure 1 shows how the addition of viscous damping changes the load’s Bode plot.

Figure 1. Effect of Viscous Damping (k_v) on the Load Bode Plot

From Figure 1, we see that as viscous damping increases from zero, low frequency gain plateaus to a value of 1/k_v. The net effect on the phase plot is to add more phase margin at lower frequencies, since the phase lag of a load with viscous damping will always be less than a load with inertia only. As a result, stability should actually improve for non-zero values of k_v. However, the response time may take a hit, depending on where the velocity open-loop unity-gain frequency is with respect to the pole frequencies shown in Figure 1. So if your system response is sluggish and the motor doesn’t seem to put out as much torque as it is rated for, you might want to investigate how much viscous damping your system has.

Before closing out this series, I want to address one more important topic. I have seen and experienced situations myself where the PI coefficients were calculated correctly, but when they were incorporated into the code, the motor either screamed like a banshee or sat there like a lump and did nothing. So what happened? In many cases, it was one of the following problems:

1. Forgetting to account for the sampling frequency effect on the GAIN of the integrator term. Figure 2 shows how to implement a typical integrator for a digital PI controller. To scale the output to match what an analog integrator would provide, we must first multiply the input signal by the sampling period “T”. In order to avoid two separate multiply operations, most code examples simply lump T together with the integrator gain term. If T is not accounted for, you will end up with an integrator gain that is MUCH higher than you anticipated.

Figure 2. Typical Implementation of a Digital Integrator

2. So far we have assumed there are no limitations on the number format itself. If you are using a floating-point processor, then you don’t have to worry about the fractional component of your PI terms. But most motor control applications are implemented on fixed-point machines for cost reasons. The good news is that TI has developed a linkable library that is in the ROM of most of our C2000 processors which solves this problem for you. It is called the “IQ Math” library which stands for “Integer Quotient”. This allows you to handle floating point values with ease on a fixed-point machine without suffering from the performance hit you typically get with a full-blown floating-point package. IQ math creates a new variable type in your code which is designated by a “Q” followed by a number. For example, let’s say you have a 32 bit variable which is typed as a “Q24” variable type. This means that any variable of this type is assumed to have a 24-bit fractional component, and an 8-bit integer part. But what occasionally happens is that someone copies TI example code into their design without realizing that our coefficients are represented in IQ format. For example, if you calculate your I-gain to be 10,000 ($00002710 in Q0 format), but you didn’t realize that the TI code assumes the variable is in Q24 format, you will end up with an integrator gain of 0.596E-3 instead of 10,000. Obviously, a big difference! If you make the same mistake for all of the PI coefficients, the motor will most likely just sit there and do nothing since all the gains are way too low. So, a word to the wise; make sure you know what numerical format your coefficients are represented by.

3. In some cases, the PI coefficients for an AC Induction Motor drive are calculated correctly and the motor runs just fine… until the motor speed exceeds its rated value, at which point the controller response becomes underdamped. The reason for this can be found back in blog 3 of this series. The motor transfer function between q-axis current and electromagnetic torque for an AC induction motor is repeated below.

Equ. 2

For speeds up to the rated speed, Id usually stays constant. But to achieve speeds beyond the rated speed, you need to reduce the flux in the machine by lowering the value of Id. You can probably see where I’m going with this. When you reduce Id, you reduce the gain of the entire velocity loop gain. If it is reduced too much, you can end up moving the unity-gain frequency to a lower value where the effect of the two poles at s=0 have more effect on reducing the phase margin. To keep the system response from changing, the Kc (or Kp) term in the speed PI controller can be increased in direct proportion to the reduction in Id.

4. Finally, the scaling of the PI coefficients throughout this series has been done assuming we want to represent real system values throughout the signal chain. For example, the output of the velocity PI controller equals the actual input reference current in amps for the current controller. The output of the current controller equals the actual voltage applied to the motor winding. But in many designs, the PI controller outputs are normalized to “Per Unit” (PU) scaling where a value of 1 represents the maximum value possible, and a value of -1 represents the minimum value possible. For example, a current regulator’s output might be scaled in such a way that 1 corresponds to 100% PWM, and -1 corresponds to 0% PWM. The advantage of this approach is that you can quickly adapt your code to different systems by simply changing your per unit scaling values. To convert from real-value scaling to PU scaling for Ka, Kb, Kc, and Kd (including the sampling period for the integrators), use the following formulae:

Equ. 3

where: Iscale is the actual current value corresponding 1.0

Vscale is the actual voltage value corresponding to 1.0

Equ. 4

where: T_i corresponds to the sampling period of the current loop.

Equ. 5

where: Vel_scale = the actual velocity value in rad/sec corresponding to 1.0

Iscale = the actual current value corresponding to 1.0

P = the number of rotor poles on the motor

Equ. 6

where: Tv corresponds to the sampling period of the velocity loop

The PU scaling for traditional parallel PI structures is:

Equ. 7

Equ. 8

where: Vel_scale = the actual velocity value in rad/sec corresponding to 1.0

Iscale = the actual current value corresponding to 1.0

P = the number of rotor poles on the motor

Tv corresponds to the sampling period of the velocity loop

To assist you with the design of your FOC based speed controller, I have created a VisSim simulation (FOC.vsm) which accepts inputs from an Excel spreadsheet (Motor.xlsx). If you open the spreadsheet, you can see the parameters for several different motor/load examples as well as the PI controller coefficients which are automatically calculated. You can also add your own motor and load parameters in the spreadsheet if you want. To create a text output file which is required by the VisSim simulation, you must perform a “Save As” option, and in the “Save as Type” field, select “CSV (Comma delimited) (*.csv).” Assuming that this file is in the same folder as "FOC.vsm", you can then open "FOC.vsm" and simply click the run icon on the toolbar at the top of the page to run the simulation. You can see the speed response (as well as plots of other system variables) by scrolling over to the right side of the simulation window. The simulation creates a step change in the commanded velocity at t=0 which saturates the system, and another step change at t=0.5sec which doesn’t saturate the system, allowing you to evaluate the system response under both conditions. If you would like to evaluate another motor /load example, simply double-click on the Motor/Load Selector Block in the bottom-left corner of the simulation window and choose a different option, as shown below.

Figure 3. Motor/Load Selector Block in the FOC.vsm Simulation File

If you would like to take this simulation out for a test drive, but you don’t have VisSim installed on your machine, simply follow the instructions below:

1. Go to Visual Solutions’ website.

2. In the top right of the browser window, click on “Create account”

3. After you create an account, click on the “Downloads” tab, and select “VisSim Software”.

4. Click on the first link on the top of the page that says “VisSim – Core simulator + UML State Charts + Analyze”

5. Run the installer program. This will install the free 60 day trial version of VisSim.

Congratulations…we made it! Thanks for investing your time with me as we have looked at different ways to make your PI control loop behave. I hope you learned some neat tricks that can help you “stay in tune” with your motor control design.

By the way, if you have suggestions for other motor control topics you would like for me to address in a future blog, I would love to hear from you. :-) And of course…

Keep Those Motors Spinning,

www.ti.com/motorblog

Android joins the Bluetooth low-energy movement

Sid Shaw — Wed, 15 May 2013 14:00:00 GMT

Without a doubt, the Bluetooth low energy market has been growing, but without broad support from the Android community there was a gap. At Google I/O, the company announced what the industry has been waiting for—support for the Bluetooth v4.0 standard, which includes Bluetooth low energy, with Android API version 18.

More manufacturers are looking at Bluetooth low energy technology to attach their “appcessories” (an accessory device that uses apps to share information) to smartphones and tablets. In fact, ABI Research predicts that there will be nearly one billion Bluetooth appcessories in 2016.

Thanks to today’s announcement, any appcessory that is Bluetooth low energy capable will be able to support Android once the APIs are available – and the good news is that it should be a fairly fast upgrade process. We will be updating our SensorTag kit to include an Android app to help speed the development of new Bluetooth Smart appcessories. And all manufacturers using TI’s CC2541, CC2540 or CC2564 will be able to update their offerings and increase the number of smartphones and tablets they can “talk” to over Bluetooth low energy.

For further assistance, the Bluetooth Special Interest Group (SIG) has launched an enablement initiative, which includes a web portal with resources for the developer community. They will also offer a Bluetooth Applications Accelerator to speed time-to-market for new appcessories that you can pre-register for on the portal.

So what does Google’s support mean for the future of Bluetooth low energy? Quite frankly, the sky’s the limit now that manufacturers can deliver Bluetooth v4.0 devices for Android, iOS, Windows 8 and Blackberry operating systems.

I hope you’re excited for the new Android-based Bluetooth Smart devices on the horizon. We can’t wait to see the innovative appcessories and other Bluetooth low energy connected devices that the Android community will dream up. Cowboid, our Android mascot, is so excited he turned Bluetooth blue and is ready and waiting with his SensorTag!

What Android Bluetooth Smart appcessory would you create?

Industrial Strength Design – Part II

Richard Zarr — Tue, 14 May 2013 19:13:00 GMT

In part 1 of this blog series I talked about harsh environments which include mines, mills, chemical plants, et. al. Designing for those environments means taking into consideration extremes which normal products (e.g. consumer goods) would never experience. We covered (briefly) some thermal issues found in these environments, but beyond high temperatures, corrosives and dirt there are dangers lurking that even humans cannot sense. I’m talking about Electromagnetic Interference or EMI susceptibility.

Most engineers think about EMI damage caused by electrical overstress. A good example of that is lightning damage - but equipment doesn’t need to be hit directly to take it out of commission. The lighting that does the actual damage may occur many miles above the equipment and may not even be seen!

In large networks where wire is strung out over miles, there can be damage caused by electrical overstress due to a phenomenon called “Cross Striking” (see the figure). This occurs when two electrically charged clouds drift near one another. An electrical potential appears between these two enormous capacitors and grows stronger as they get closer. On the ground, an opposite charge appears on the cabling caused by the static charge in the cloud above. It appears very slowly so no apparent problem is seen – yet.

Once the electric field strength between the two clouds exceeds the break-down voltage of the air between them, a bolt of lightning forms and rapidly dissipates the charge. This rapid discharge has now left an extremely large charge on the wires below with nothing holding it. This charge also rapidly dissipates causing extremely high voltage spikes on the cable which typically will destroy anything unprotected on either end. I know this… I’ve seen it first-hand. Nothing but ashes and a hole where my transceivers used to be! It just makes you go “hummmm… wow!”

To protect against this type of “invisible” damage, gas discharge tubes, spark gaps and ESD diodes need to be placed on either end of the cables to provide a path for the current to travel as the charge dissipates. This will keep the voltages seen by drivers, receivers or amplifiers within absolute maximums and prevent damage.

Another type of EMI susceptibility doesn’t damage the circuits, but actually causes them to fall out of specification. This problem often manifests itself in industrial environments where strong RF fields are used (e.g. microwave heaters in processing plants). It can also be caused by deliberate transmissions such as radio towers. This phenomenon can be seen by placing a cell phone next to most speaker phones while a call is active. A humming or clicking is often heard in the speaker phone due to interference with the transmitter in the cell phone. This is caused by the RF energy impinging on parasitic (or intentional) diode structures within amplifiers and injecting currents into the circuit.

The rectified signals can show up as offsets in the output of precision amplifiers as well. This is the critical problem in industrial systems which make very precise measurements in processes that require extremely accurate temperatures or pressures. To combat this, semiconductor designers add additional circuitry to harden the device against these external fields. An example of this is the LMP2021 or LMP2022 (dual) which is EMI hardened for precision measurements. For more detail on this topic check out application note SNOA497b – A Specification for EMI Hardened Operational Amplifiers. This white paper discussed a new parameter called the EMIRR or Electro-Magnetic Interference Rejection Ratio which is used to quantify the susceptibility of op-amps to EMI.

I hope this post sheds some light on some of the unseen perils that can damage or derail your precision circuits. For more information on industrial components, see TI's industrial offering page. I’ll cover some more ideas on helping build industrial strength designs in my next post… I welcome your comments or ideas as well. Till next time…

Xiaolin Lu First Woman and TIer Named Co-Chair of Jonsson School’s IAB

Around TI — Tue, 14 May 2013 13:00:00 GMT

Tier Xiaolin Lu, currently the smart grid R&D manager, has made history twice: she’s both the first woman co-chair and first TI employee to be appointed to the University of Texas at Dallas’ Jonsson School Industrial Advisory Board.

The IAB is a council of more than 60 representatives of close to 40 companies and organizations. Their purpose is to provide an industrial perspective on the direction and strategy for the school’s curricula, as well as to promote the school among local industry, school districts, and North Texas overall. With 17 years of experience at TI and over 22 U.S. patents under her belt, Lu is in a prime position to guide students looking to break into her industry.

"Being an IAB co-chair gives me the opportunity to serve the community by helping to build a state-of-the-art, high-tech engineering and education facility for Texas," Lu said. "In this board role, I will also be able to strengthen the relationship and impact that companies like TI have with UT Dallas and help to further develop the students' critical innovative skills by influencing the direction of the school's science, technology, engineering and math programs."

TI’s founders, Erik Jonsson, Eugene McDermott, and Cecil Green were responsible for the establishment of the Erik Jonsson School of Engineering and Computer Science with the goal of providing TI’s engineers and scientists with the best, most advanced training. Fostering the next generation of engineers is and has always been a top priority for TI. Lu’s involvement with the IAB is yet another example of TI’s longstanding partnership with UT Dallas.

New MSP430 Tool Deal Available!

William Cooper — Tue, 14 May 2013 04:36:00 GMT

Interested in achieving extended battery life in portable measurement applications? Give our MSP430AFE2xx devices a try!

We will make it a little easier... for the next two weeks you can purchase the MSP-TS430PW24 target board for only $30 (new price reflected in cart). Order today!

LaunchPad + Energia = Wireless Light Switch

William Cooper — Tue, 14 May 2013 04:07:00 GMT

Have you ever hesitated to implement your ideas for fear of the long road ahead? Never again! The LaunchPad and BoosterPack ecosystem was a great place to start when implementing an idea in hardware, but until recently it was lacking a development environment that matched its simplicity and ease of use. I'll walk you through this below, but for a first hand experience visit Maker Faire on the West Coast!

Now that is a thing of the past. Energia is a community created and driven software platform based on the Wiring framework. This platform simplifies programming to the use of high level functions, so you can say goodbye to hunting through datasheets and changing register values just to blink an LED.

What now? With LaunchPad and Energia, you can create a prototype in minutes! To demonstrate this, I decided to create a wireless light switch. On the hardware side, I created two pieces: A MSP430 LaunchPad connecting to a TRIAC circuit, for turning the light on and off, and a MSP430 LaunchPad with a Cap Touch BoosterPack and a community developed battery BoosterPack for remote control. Now, the most important part of a wireless light switch…Wireless! I used two Air BoosterPacks featuring the CC110L sub 1 GHz radio and created by Anaren.

On the software side, I used only Energia. I leveraged a cap touch library created by a 43oh community member and a library Anaren created for their Air BoosterPack. Check out the result!

(Please visit the site to view this video)

Rapid prototyping and fun projects are just a little easier with Energia around and I am so excited to create more projects like the wireless light switch above! Please leave a comment below to share your experiences with the great combo of LaunchPad and Energia. I can’t wait to see what else is out there!

Handy Gadgets and Resistor Divider Calculations

Bruce Trump — Mon, 13 May 2013 23:34:00 GMT

Handy gadgets make our engineering life easier—the little special purpose computer programs or spreadsheets that you might find or create yourself.

Back in the old days, engineers used nomographs. These are graphical aids that solve common multivariable problems of all sorts. Calculators and desktop computing caused their decline so you seldom see them today. I still use a variant of one—an old cardboard R-L-C reactance slide rule given to me in my first electric circuits class back in the ‘60s. It helps me find approximate values in the right impedance range when I’m positioning poles and zeros. I think better with it in my hands.

I believe that the graphical nature of a nomograph can aid in visualization and optimization. Has something has been lost when we just plug numbers into a computer?

In previous blogs, I’ve provided gadgets for calculating op amp noise and 1/f noise. Here is another, an Excel sheet that calculates resistor values for a three-resistor divider with a voltage reference to offset the output voltage. For example, if you have a -10V to +10V input and you want attenuate and shift it to a 0 to 3V output, this gadget calculates the resistor values.

(Please visit the site to view this file)

It’s a sub-circuit that is often needed in signal processing. The math is a bit messy, so if you solve it once you probably don’t want to do it again. It’s the type of task that is worth the time to create a gadget. The equations are in figure 2, if you don’t want to use the worksheet. I refined it a bit, adding some checking for out-of bound values and minimum required value for the reference voltage. Try it and see. With the annotations I think you’ll find it easy to use.

Excel (or equivalent) is pretty handy for calculations like this but I find it awkward for some types of programs. I have some gadget programs that parse long files to manipulate data. I’ve used various forms of BASIC for this through the years but now I use Excel’s Visual Basic (macros), loading data into the associated worksheet to use its graphing capabilities. I wouldn’t publish these gadgets. Excel macros are so easily written or modified to create serious damage that they’re scary. I only give them to close associates and I’m not even sure they trust me. :-)

What handy gadget design aids have you made? What ones do you wish you had? Do you use any old-style nomographs or slide-rules like mine?

Thanks for reading and your comments are welcome below,

Bruce email: thesignal@list.ti.com (Email for direct communications. Comments for all, below.)

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