EEWeb Pulse - Volume 49

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PULSE

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Issue 49 June 5, 2012

Ferenc Marki and Christopher Marki Marki Microwave

Electrical Engineering Community

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TA B L E O F C O N T E N T S TABLE OF CONTENTS

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Ferenc Marki and Christopher Marki MARKI MICROWAVE Interview with Ferenc Marki - President and Christopher Marki - Director of Operations

Featured Products

11

What is a PCB Array?

13

BY PETER BRISSETTE WITH BAY AREA CIRCUITS An in-depth look at a new connected board assembly method that can expedite the manufacturing process while reducing the costs.

Sensors, Smart Sensors, and Sensor Control Electronics

18

BY TAMARA SCHMITZ WITH INTERSIL A discussion of a variety of smart sensors and their impact on the robotics industry.

RTZ - Return to Zero Comic

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Marki INTERVIEW

Marki Microwave Can you tell us about your work experience before founding Marki Microwave?

FM: I’ve been working in the microwave industry since 1971. I started my career at Watkins Johnson (WJ), where I started, almost from day one, as a mixer designer. I eventually moved on to Avantek, and then Western Microwave where I continued developing new, advanced mixers, especially most of the triple balanced mixers on the market today. In 1991, I started Marki Microwave with the goal of becoming the premier high performance mixer vendor in the world.

CM: Because of my dad’s contacts, I was able to take internships at both Lucent and Anritsu while I was still an undergrad at Duke. I decided to avoid entering the real world after college and instead went to

Ferenc Marki - President (left) Christopher Marki - Director of Operations (right)

UC San Diego to pursue a PhD in Photonics (high speed fiber optics, actually). While at UCSD, I gained some valuable experience working

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on DOD projects and consulting for a startup called Ziva Corporation.

After 5 years of chasing government money, though, I realized that

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FEATURED INTERVIEW

Ferenc and Christopher

INTERVIEW

What have been some of your influences that have helped you get to where you are today?

FM: There a many talented individuals who have helped me throughout my career. From a mixer designer perspective, two of the most influential and brilliant minds I was inspired by are Bob Maou and Don Neuf (Miteq). Bob and Don’s work always pushed me to advance the art of mixer design.

Perhaps most importantly, however, is the influence of my wife, and Marki Microwave Vice President, Christine Marki. In the early 90s, Marki Microwave was very small and there was no guarantee that our company would survive. Christine’s steady and organized approach to the company finances and procedures were as important to our survival as my understanding of high performance mixers.

CM: Obviously, my dad. Beyond that, though, are my two professors from UCSD: Sadik Esener and Stojan Radic. Sadik taught me how to think about technology development in a way that made me self-reliant. That skill is often under-developed in graduate students because their professors simply give them problems to solve. Sadik made me fend for myself to define my projects, which is invaluable now that I am Director of Operations at Marki Microwave.

Stojan Radic is perhaps the more

brilliant experimental scientist I’ve met. He taught me how to do good science. Stojan always had the right combination of blue sky dreaming with a practical “just get it done” engineering attitude. Beyond that, I think both my father and myself look at Dr. Richard Feynman as the greatest role model for our profession. We both devour any and all Feynman literature…the man was a down to earth genius.

What are your favorite hardware tools that you use?

FM: All of my test equipment. I have boxes that still say “HP” (now Agilent) and “Wiltron” (now Anritsu) on the front. I am an empirical

weight in gold is the “Ecal” module that performs fast calibration of the PNA. I can calibrate the box while I go for coffee…now that’s service.

What are your favorite software tools that you use?

FM: I don’t use any software tools, just intuition. I don’t even have email.

CM: HFSS for 3D simulation work.

Microwave Office for schematic work. MATLAB for theoretical work.

LabView for test setup automation.

What is the hardest/trickiest bug you have ever fixed?

scientist, and experiments are how I learn my trade. There is no substitute for high quality test equipment.

FM: When I started working on mixers, there was very little literature explaining how mixers actually worked, especially when it came to describing effects like intermodulation distortion, twotone, and the simple fact that all mixers require a specific LO drive.

We had to develop our intuition about the cause and effect in our designs and work tirelessly at the lab bench to achieve better and better performance. People called mixers “black magic” in those days for good reason, they were quite mysterious to even so-called “experts”.

CM: The Agilent PNA-X vector network analyzer changed my life.

Experiments that once took my dad 20 minutes to setup are now available to me at the click of a mouse. We now have a full measurement suite saved in the PNA-X that can measure almost any mixer metric with great ease compared to the “old school” way of doing it. Of course, my dad refuses to use the box. The other hardware worth its

CM: I wrote an entire program dedicated to designing ultrabroadband directional couplers in MATLAB. All you have to do is plug in the number of sections, the coupling value, and the coupling ripple, and the program gives you a physical circuit that I then send to the board house for fabrication. During the development, I had to figure out a way perform a calculation involving a nonlinear set of equations with

Don’t assume good ideas have already been tried, or simple ideas are too obvious.

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FEATURED INTERVIEW

my dad had much more to share about engineering and business development than anyone I knew, so the obvious choice was to learn the family business.

INTERVIEW

What is on your bookshelf?

FM: I am reading Julian Barbour’s work about the concepts of “timeless physics” and Machian dynamics. I have always been interested in people who challenge conventional wisdom, so someone who claims that time is an illusion is worth reading about. As I like to tell my son, “don’t accept sacred cows, they will make you a less creative engineer.”

CM: Besides physics and engineering text books, very little. My mom would try and make me read more as a child (she’s an English teacher), and now my wife does the same. Eventually they will concede that video games are much more fun.

Do you have any tricks up your sleeve?

CM: Yes. Marki Microwave does not patent our work, so everything is essentially a trade secret. Suffice to say, any time we call something “proprietary”, it is our way of saying “we ain’t telling”.

What has been your favorite project?

FM: I spent my teens and early 20s as a jeweler, so I always loved designing the mechanical packages for my mixers. The evolution of RF/ microwave packaging has always been fun as we started with pin packages and hermetic packages, and then moved on to carriers and then surface mount packages. It seems that everyiteration in the packaging evolution brings an interesting new set of problems, and they are always fun to solve.

Most of my former competitors are out of business, or do not develop new mixer technology. Marki is, almost by default, the only viable option for customers who need the highest performance mixers money can buy.

CM: All of the high IP3 mixer work my dad and I perform tends to be very exciting. Our customers seem to have an unquenchable thirst of bandwidth and better mixer linearity. Almost every new design we release is sold within days,

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and most of those designs are in some way a world record. When you can release high performance equipment and sell it, that is very satisfying.

Do you have any note-worthy engineering experiences?

FM: Last year, Microwave and RF Magazine inducted me into the “Microwave Hall of Fame”. It was gratifying to be recognized for my pioneering work in mixer technology. Since I don’t publish articles or patents, and many of my customers work on classified projects, the recognition of my peers in the industry was humbling.

CM: As a 4th year graduate student, I had to take the red eye to Washington DC to visit a DARPA project manager because my professor had fallen ill at the last minute. It was the first time in my life where my knowledge and skills actually had an obvious end game: to produce new technology that people could actual use. It turned out to be a rather innocuous meeting, but it was exciting to see how all those hours in the lab and in the classroom could turn into have some very smart and talented people ask for your expertise.

Do you have an experiential stories you would like to share?

CM: On my 25th birthday, I presented about 6 months of experimental results to my PhD Advisor. I was very proud and thought it would jump start my grad career. At the end of my talk, he says to me, “so what? Why should anyone care”. I was very disheartened. I realized after a few days, though,

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FEATURED INTERVIEW

more than 20 variables. I spent weeks on the problem, going between MATLAB, MathCad and Mathematica trying to figure out how to do it. I eventually figured out an approach in MATLAB, and the reward was a fully functional, rock solid design program that I still use today for all of my new designs. Last year, I modified the design to make a very bizarre design which was a 6 dB coupler with a 155 degree phase shift from 2-20 GHz…that was hard!

INTERVIEW

What are you currently working on?

FM: New T3 mixers. I have a prototype mixer that covers 10 MHz to 30 GHz, I’m pretty sure that is a world record of some kind. I’m also deeply involved in understanding the impact of local oscillator noise (AM and PM) on high dynamic range frequency conversions. Little literature is available on this topic, and the issue is becoming more relevant for modern systems.

CM: My role is now to oversee most of the new product development.

My dad is incredibly productive, so taking his ideas into marketable products is a full time job by itself…the phrase “herding cats” comes to mind. I am also working on new ways of building my dad’s original designs that miniaturize the products, and reduce the assembly complexity, which is the primary cost driver. Beyond that, Marki just

released its first line of pseudotest equipment. The line is called the “Marki Meter” and is an inline power monitor from 10 MHz to 8 GHz. This idea has been kicked around for years, since my days at UCSD, and a good friend who I hired out of UCSD is the lead designer.

We look forward to advancing that product line in the coming months and years.

Can you tell us more about Marki Microwave? What are some of the major changes the company has seen since its founding over two decades ago?

FM: Most of my former competitors are out of business, or do not develop new mixer technology. Marki is, almost by default, the only viable option for customers who need the highest performance mixers money can buy. We are in a niche market, so larger companies cannot justify chasing our market because the ROI would not be justifiable. We also have the highest linearity mixers in the world with our T3 line (invented in 2005), and this line represents a complete paradigm shift in mixer technology…it is even obsoleting my own legacy designs. Its always better to obsolete yourself, before your competitor does.

CM: Two decades ago I was still in Little League; I don’t play in Little League anymore. Interestingly, many of our employees have been loyal team members to my father since the early 80’s. For me, I grew up with many of these people. In that sense, very little has changed.

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How large is the company / how many people work at Marki Microwave?

Around 45 What is your work culture like?

CM: I think of Marki as a research group that actually commercializes our work into products. We can’t afford the risk of extremely “blue sky” ideas, but we are extremely entrepreneurial in spirit and are always looking to advance the art of our technology. We are addicted to high bandwidth and high performance. Our roots in the Silicon Valley also instill in us a sense of pushing hard for progress and not relaxing on old technology.

The RF/Microwave business is sometimes very slow to change. We perform new development work, regardless of if a customer asks first. We are inspired by people like Steve Jobs, who knew what the customer wanted before they knew themselves.

How does Marki Microwave continue to be the premier manufacturer of microwave mixers worldwide, offering the industry’s most comprehensive line of signal processing products up to 65 GHz? FM: We focus on performance first, and cost later. In other words, to make the best, you cannot let artificial barriers like BOM cost and “market data” sway your quest to figure out the limits of your design.

Market driven boundary conditions will come up later, after you have figured out what the technical limits are. If you want to be the Mercedes of your niche, you cannot accept the older technology. You must always

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FEATURED INTERVIEW

that my advisor had a point: doing work for the sake of doing work is ok if you are in the pure sciences, but not if you are an engineer. If you don’t work on problems that will help people (business people call this “adding value”), then your effort is meaningless. My professor was reminding me that I had to have a good reason for doing countless hours of experiments, otherwise I’m wasting everyone’s time and money. A few days later, I buckled down and started writing out the theory behind my work to explain the big picture concept and how the experiments prove certain design constraints of high spectral density fiber networks, for which my first ever paper was published. Always look at the big picture!

INTERVIEW

Can you tell us about the products lines Marki Microwaves produces?

CM: The main theme is “broadband and high performance.” We do not focus on commodity markets like the cell phone or telecom market because we cannot compete. We design and manufacture 100% of our products in the USA, and commodity work almost necessarily requires overseas operations. Most of our products are market leaders in performance, and we are very receptive to custom work. Currently, our top lines are Mixers, Multipliers, Amplifiers, Power Dividers, and Couplers.

About you and your father: Are there any projects you and your father just can not agree on or do not work well together on?

CM: We disagree almost on a daily basis. Since this is science, the disagreements (usually) stay within the lab. I am much more conservative than my dad, who is a maverick thinker. I prefer a more systematic approach while my dad prefers getting his hands dirty. I trust my dad implicitly and almost always differ to his experience, but sometimes I can’t help but disagree.

Marki males are very excitable (volatile?) people. I can’t think of a situation, though, where we didn’t ultimately both agree about how to proceed.

What are some of the important life / engineering lessons your father has taught you?

CM: Too many to innumerate. If I pick one, it is simple: “You can’t fool Mother Nature”. In other words, the most important thing to remember is that you must base your decisions on the technical merit of the argument, not on the

We focus on performance first, and cost later. In other words, to make the best, you cannot let artificial barriers like BOM cost and “market data” sway your quest to figure out the limits of your design. non-technical noise created by business processes. People believe in many “sacred cows” in science and business, you should question every one of them as a scientist and entrepreneur.

Working with your son, has he taught you anything or brought a different perspective being from a younger generation?

FM: When Christopher started

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working here, I tried explaining to him the “grand theory of mixers.”

I quickly realized that I could not answer many of his questions. He and I are very physical thinkers, and we both did not like the “hand waiving” explanations I was coming up with. He and I began to come to the conclusion that my understanding of certain aspects of mixers was very poorly understood, especially when it came to the physical understanding of how two-tone and IMD are generated.

Our early work together forced us to create an entirely new physical understanding of how my T3 mixers work, and this has led to several performance breakthroughs that we never thought were achievable.

Is there anything that you have not accomplished yet, that you have your sights on accomplishing in the near future?

FM: To this day, I have always found our understanding of the noise mechanisms in frequency converters to be unacceptable.

Specifically, people consistently blame mixers for causing noise figure degradations in converters, without seeing the system as a whole. Truth is, local oscillator noise (AM and PM) have a dominant impact on mixer noise. While some people know this, few seem to appreciate the fact that almost all the noise mechanisms in mixers make a difference, and the mixer itself (i.e. the diodes) are almost never to blame. This is complicated further by the insufficiency of most test equipment to actually measure noise figure and, more importantly, signal to noise ratio (SNR). It seems to be one of those areas where little

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FEATURED INTERVIEW

innovate on your old ideas. You have to accept the fact that everything we do today is inferior to what we will do tomorrow. If you assume there is a better way, your creativity will help you get there.

INTERVIEW out a way of getting the product into my customer’s hands.

CM: Establish Marki Microwave as a leading brand in products beyond mixers. I would also like to see my dad take a vacation every once in a while, he’s twice my age and works twice as much…I feel so lazy.

CM: More T3 mixers. Smaller packages with better performance.

The widespread adoption of the Marki Meter product line. Beyond that, it all depends on how creative we can be.

What can we expect to see from Marki Microwave in the near future?

FM: Whatever it is, it’ll be something that you’ve never seen before. I’m an opportunist, if it makes sense, and the performance is there, I’ll figure

What challenges do you foresee in our industry?

FM: Complacency. An inability to attract younger talent. The over reliance on software design tool in lieu developing one’s intuition experimentally.

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CM: Most of the young talent going into software instead of hardware.

Also, the US needs to streamline the VISA, Green Card and citizenship process for talented, foreign born engineers who want to come to the US. What advice would you give to new students just getting into the engineering world?

CM: Don’t assume good ideas have already been tried, or simple ideas are too obvious. ■

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literature exists…someone should get a phd on this topic.

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TECHNICAL ARTICLE TECHNICAL ARTICLE

WHAT IS A

PCB ARRAY? Peter Brissette Bay Area Circuits

An array is combining a single PCB multiple times to make a larger array of connected boards.

This process is referred to as “stepping out” the individual boards. It is often referred to as “step and repeat.” Other terms used to describe an array are: panelized, stepped out, palletized and rout and retain.

Why would someone want an array?

The reason a manufacturer would want their board in array is to help them with the manufacturing process. It gives them the ability to load the parts at a much faster rate because they can do the whole array at once instead of loading one board at a time. The boards are loaded using automated equipment referred to as “pick and place” machines. This equipment simply picks up parts (normally surface mount devices) and places them down on the board.

Arraying the boards will typically raise the cost of the individual boards. This happens because you can get fewer boards on a production panel when they are in an array versus when they are run as individual boards.

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Even though the individual board cost will go up, the cost of assembling the boards is less because of the array configuration.

General Guidelines Each electronics assembler and manufacturer will have their own specific guidelines for how they want to have their arrays set up for manufacturing. These guidelines provide some ideas of general practices that are fairly common.

Size of the array: Array sizes range from 8 × 10 inches to 10 × 12 inches as the overall largest size. If the PCB manufacturer is using a production panel size of 18×24 with a usable space of 16×22, then the best fit of the largest array will be 7.8 × 10.8 inches. That will allow at least four arrays up on the panel. If the array size is larger than that, you will only be able to get two arrays up and the cost per board will go up significantly. Smaller array sizes can be used for smaller individual boards and still have a good yield for each panel.

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TECHNICAL ARTICLE TECHNICAL ARTICLE

This is a .125 tooling hole on a .500 rail

Spacing between boards and rail is .100

This is a fiducial mark that is .050 in diameter, it goes in three locations on the rails. It is .500 from the top edge of the board on the long rail side. (See PDF)

Figure 1

Rails: Rails are extra PCB material that are added to the sides of the array to allow for easier handling during the assembly process. The rails could be on all four sides of the array or only on two sides. If you only have it on two sides, then you can usually get a few more pieces up on the panel, which will help the per board cost.

There are two options that we just mentioned for “depaneling” the boards—that is, how you separate the boards after they are assembled. The options are scoring or tab rout.

Scoring: Scoring means making a small “V” groove along the length of the board where they will be separated. The

Fiducials: Typically, three fiducials are needed on an array and are placed on the rails. The ideal size is .050”. The fiducial is a copper pad circle with the same finish as the rest of the board. This provides alignment targets for the automated assembly equipment to get things lined up.

Some manufacturers may require fiducials on each individual board as well. However, for the most part, there are pads or other features on the individual boards that can be used to provide additional alignment targets.

This Array shows scoring with tooling holes and fiducials.

The rails are on two sides and in between boards as well (which is a little unusual).

Tooling Holes: Tooling holes in the four corners of the array (in the rails) is fairly common as well. Again, these are used to aid in alignment and orientation when assembling the board.

The typical size is .125” and they are non-plated.

Spacing of the array: The spacing will depend on whether the array is scored or routed. For tab rout, the spacing is .100 in most cases.

With scoring the boards and being placed next to one another, there is no spacing needed.

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Figure 2

groove is typically 1/3rd on top, 1/3rd on bottom leaving 1/3rd of the material remaining in place to hold the boards together.

When scoring, there should not be any parts placed within .250” of the edge of the board. If they are closer than that, there is the possibility that the parts could

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TECHNICAL ARTICLE

It’s kind of hard to see, but this is what is called the mouse bites or perforated holes on the tabs. Makes it easier to break apart.

X Outs An X out is when one of the individual boards on the array does not pass the test and is marked out with a marker.

Some manufacturers will allow a certain percentage of X outs on the order, while others may require there be no X outs on any of the arrays. By having no X outs, it will make the board cost a little more since the PCB manufacturer may need to make a larger number of arrays in order to meet the order requirements depending on their yields.

Figure 3

Breakaway Tab Geometry 0.050”R 0.268” 0.017” panel frame

0.005”

Many will use the program Kwickfit for calculating arrays, which is a very handy tool.

PCB 0.027”

How do you calculate the size of the array?

0.027” 6 equal spaces @ .090”=.180”

0.020” DIA Unplated 9 Places

If you have Kwickfit, here are the steps to getting a best fit array: • Panel size set at 18 × 24 with 1 inch margins

Typical Panel Frame/Rail Perforation 0.250” Frame 4 equal spaces @ 0.045”=.180” 0.095”

0.020” DIA Unplated 5 Places

• Select best fit array • Enter individual board dimensions • Max size of 7.8 × 10.8 • Min qty of 1, Max qty of 100

Figure 4

• Click Calculate.

• If you don’t have kwickfit you can also do this manually.

come loose during the depaneling process. If the board thickness is more than .062” and the score line is long, it can require a significant amount of force to separate the boards.

Tab Rout: Tab rout arrays will leave a small tab on all four sides of the board attached to the other boards or the rails. This type of array is not as stiff as the scored array, but can be easier to break apart.

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• A spreadsheet or a calculator makes this easier of course.

• Assume the largest X dimension will be 7.8 and the largest Y dimension will be 10.8.

• Use the smallest dimension of the individual boards as the X dimension.

• Step One is determine your Rail Size

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TECHNICAL ARTICLE

Tabs are typically one on each side of every board and usually .050” wide. They will usually have small holes drilled on the edge of the tab at the board out line.

Those small holes are referred to as “mouse bites” or “perforated holes.” I have even heard them referred to as “rat bites.” Either way, they make it easier to break the tabs off of the board. They do leave a rough edge, so some additional sanding or grinding might be needed to smooth them out.

TECHNICAL ARTICLE • Step Four add it all together

• If your rail size is .5 you will double that (rails on both side) and then deduct that from the total available dimension for the X dimension.

• Note: You will have to add .1 to the total of the boards to get the correct overall dimension since you have spaces on both sides of the boards.

• That would then be 1 inch deducted from 7.8” = 6.8” inches. That is your “useable” space now for your array in the x dimension.

So here is the total for the X dimension:

• Step Two is to add your spacing to the size of the board.

• X Dimension = _______ • Spacing = __________ • For example your board is 1 inch and your spacing is .1. Add those together and you have 1.1 inches.

• 6 pcs * 1.1 = 6.6 + .1 (for the extra space) = 6.7 + 1 (for rails) = 7.7” in the X dimension Then do the same process for the Y dimensions: • 10.8 – 1 = 9.8” useable space • 9.8 / 1.1 = 8.9 (have to round down) so equals 8 wide in the Y dimensions

• Step Three is determine how many will fit.

• 8 * 1.1 = 8.8 + .1 = 8.9 + 1 (for rails) = 9.9” in the Y dimension.

• Divide 6.8 by your individual board size with the spacing added. In this case 6.8 divided by 1.1 = 6.1

So you will get 6 × 8 up (48 pcs) and the overall size will be 7.7 × 9.9 with .500” rails and .100” spacing.

• So you will be able to fit 6 boards of 1” size in the x dimension using .1 spacing with .5 rails.

Now you can do this manually like I have shown you here. Or, you can just visit our website and give our Array Calculator a try. It will do all the math for you and make a nice graphic image for you to see.

About the Author Peter Brissette, is a Printed Circuit Board specialist with more than ten years in sales and marketing in the PCB industry. His specialty is in taking complex technical information and making it easy to understand. You can read his regular PCB Technology blog posts here. ■

Figure 5

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• Rail Size = _______

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Features

The ISL80111, ISL80112, and ISL80113 are ultra low dropout LDOs providing the optimum balance between performance, size and power consumption in size constrained designs for data communication, computing, storage and medical applications.

These LDOs are specified for 1A, 2A and 3A of output current and are optimized for low voltage conversions.Operating with a VIN of 1V to 3.6V and with a legacy 3.3V to 5V on the BIAS, the VOUT is adjustable from 0.8V to 3.3V. With a VIN PSRR greater than 40dB at 100kHz makes these LDOs an ideal choice in noise sensitive applications. The guaranteed ±1.6% VOUT accuracy overall conditions lends these parts to suppling an accurate voltage to the latest low voltage digital ICs.

• Ultra Low Dropout: 75mV at 3A, (typ)

ISL80111, ISL80112, ISL80113 1.2V ±5% VIN

9

CIN 10µF

3.3V ±10% VBIAS

CBIAS 1µF

EN OPEN DRAIN COMPATIBLE

VOUT

VIN 10 VIN

VOUT 2

4 VBIAS

PG

7 ENABLE

ADJ

1.0V VOUT

1 COUT 10µF

6

PGOOD R3 1.0kΩ

3

R4 1.0kΩ

GND 5

• ±1.6% Guaranteed VOUT Accuracy for -40ºC < TJ < +125ºC • Very Fast Load Transient Response • Extensive Protection and Reporting Features • VIN Range: 1V to 3.6V, VOUT Range: 0.8V to 3.3V • Small 10 Ld 3x3 DFN Package

Applications • Noise-sensitive Instrumentation and Medical Systems • Data Acquisition and Data Communication Systems • Storage, Telecommunications and Server Equipment • Low Voltage DSP, FPGA and ASIC Core Power Supplies • Post-regulation of Switched Mode Power Supplies

DROPOUT VOLTAGE, BIAS = 5V (mV)

An enable input allows the part to be placed into a low quiescent current shutdown mode. A submicron CMOS process is utilized for this product family to deliver best-in-class analog performance and overall value for applications in need of input voltage conversions typically below 2.5V. It also has the superior load transient regulation unique to a NMOS power stage. These LDOs consume significantly lower quiescent current as a function of load compared to bipolar LDOs.

• Excellent VIN PSRR: 70dB at 1kHz (typ)

FIGURE 1. TYPICAL APPLICATION SCHEMATIC

IOUT = 0A

IOUT = 2A BIAS = 5V VIN = 3.3V VOUT = 2.5V COUT = 10µF 100

1k

IOUT = 3A

10k FREQUENCY (Hz)

100k

1M

FIGURE 3. VIN PSRR vs LOAD CURRENT (ISL80113) March 30, 2012 FN7841.0

ΔVADJ +25°C NORMALIZED (%)

PSRR (dB)

IOUT = 1A

60

0

3A

80 70

2A

60 50 40

1A

30 20 10 0

-40

25 85 TEMPERATURE (°C)

125

1.015

80

20

90

FIGURE 2. DROPOUT VOLTAGE OVER-TEMP AND IOUT

100

40

100

1.010 1.005 1.000 0.995 0.990 0.985

-40

0

25 85 TEMPERATURE (°C)

125

FIGURE 4. ΔVADJ vs TEMPERATURE

Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2012 All Rights Reserved. All other trademarks mentioned are the property of their respective owners.

Sensors, Smart Sensors & Sensor Control Electronics TECHNICAL ARTICLE

TECHNICAL ARTICLE

Tamara Schmitz

Senior Principal Applications Engineer And Global Training Coordinator

For

safety, accuracy and convenience, automation is providing improvements in everyday applications.

Consider the precision and advantages of computerassisted surgery or the array of automation now available in automotive applications like blind-spot detection, automatic bright light adjustment of rear view mirrors, back-up cameras or parallel parking assistance.

However, the industrial segment is the first sector to embrace automation. Major advances in robotics and factory automation have lead to production efficiency and factory safety. The four major technology sectors that have enjoyed these investments are sensors, transducers, motors and control electronics.

Here we will discuss the role of sensors and their

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development. Weâ&#x20AC;&#x2122;ll provide an example to help you understand the distinction between simple and smart sensors. In addition, we provide a few examples of support devices whose high quality enhances the sensors they accompany. As these devices improve, the entire robotic system will benefit from their enhancements.

Smart Sensors and Simple Sensors Since they lack human-like powers of observation, robotic systems need sensors to view and interpret their environment. Consider the seemingly simple act of picking up an object; first, the system must locate the object, and after deploying an arm, a sensor is needed to ensure the approach toward the object. Often, another sensor signals when contact is madeâ&#x20AC;&#x201D;gripping is an art all by itself. How much pressure is needed to secure

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TECHNICAL ARTICLE TECHNICAL ARTICLE

VDD 2

ALS Photodiode Array Command Register

Light Data Process ALS and IR IR Photodiode Array

Dual Channel ADCs

Data Register 1

ADDR0

5

SCL

6

SDA

Interrupt

7

INT

IR Driver

8

IRDR

I2C IREF FOSC

4

3

REXT

GND

Figure 1: Block Diagram of the ISL29028A ambient light and proximity sensor.

the object without crushing it? These actions of motion control typically involve accelerometers in conjunction with continuous position feedback from other system sensors. This simple example assumes that the item is stationary and doesn’t exhibit certain material behaviors such as magnetism or heat, which can be detected by specific sensor types.

Typically, the information from this network of sensors is processed in a centralized microcontroller. This setup is straightforward and simple—it exhibits the clear advantage of centralized control, centralized power requirements and simpler algorithm development. This type of system may enhance flexibility, but may also limit maximum performance. Consider that there is a risk that the microprocessor may not be able to calculate fast enough or even to provide service interrupts quickly enough. These limitations can cap the achievable robotic performance.

The use of smart sensors moves the decision making process to the point of interest (in this case the arm and “the picker”) and thus provides opportunities for improved capabilities. It also allows multiple events to be easily controlled. Remember that distributed control makes the system design much more complex, but removing the central bottleneck allows the system’s

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capabilities to be significantly enhanced.

Sensor Interfaces It is no surprise that technology companies have been and will continue to develop and deploy devices to propel the field of robotics to the next level. It is of particular interest when the sensor and related electronics can be integrated into an easy-to-use, monolithic solution.

One of the most popular types of sensors is the proximity sensor. These sensors are found in all sorts of consumer and communications products, ranging from vending machines, ATMs, security systems, cell phones and leading-edge personal computers. They can not only provide positioning information, like in the robotic example above, but are also used in safety systems and intrusion detection. Proximity sensors operate with infrared wavelengths that are invisible to the human eye.

This allows a system to monitor how close objects are without constantly blasting visible light in a variety of directions, possibly even distracting people nearby.

In cell phones, a proximity sensor allows the phone to detect when the user has brought it to his or her ear to engage in a phone conversation. During this time, the screen can be disabled, saving power and increasing

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TECHNICAL ARTICLE A popular proximity sensor is the ISL29028A. It houses an ambient light sensor and a proximity sensor along with a built-in IR LED driver and I2C interface. The ambient light sensor allows the system to reduce the screen brightness in lower light situations, which is more pleasant for the user as well as a power-saving technique. The IR LED driver sends out short bursts of current to an IR LED. An object within a few centimeters will reflect this signal to the proximity sensor, alerting the system to a nearby object.

An example of increasing the smarts of a sensor is the interrupt scheme of the ISL29028A. The microcontroller does not have to continually pole the sensor to search for an object approaching the phone. Instead, the ISL29028A provides an interrupt signal. This interrupt signal allows the microcontroller to power down and wait for the sensor to inform it that an object is approaching. This allows for minimal loading on the microcontroller and an obvious savings in power.

Smart Sensor Support To function appropriately, smart sensors require strong support chips, including very low power and low noise signal conditioning elements. High input impedance instrumentation amps, such as the ISL28274 from Intersil, provide the rail-to-rail inputs and outputs required in many sensor applications. In addition, the amps exhibit extremely low input bias current and high CMRR needed

for the strain and pressure sensing used in tactile robotic applications.

Another support IC sensor amplifier example, which is an important contributor to advanced product design, is the ISL28133 micropower chopper stabilized op-amp.

This breakthrough design is optimized for single supply operation from 1.65 to 5.5 V, with only 18 μA quiescent current and 8 μV, max. input offset voltage. Since it is a chopper stabilized op-amp, it continually measures and cancels input offsets, so the entire offset over temperature is just 0.075 μV/°C maximum. While showcasing rail-torail inputs and outputs, the ISL28133 still can provide strong noise specifications for this type of IC: 1.1 μVP-P, typ. noise (0.01 Hz to 10 Hz).

Robotics, in various forms, has stimulated the imagination of many science-fiction writers as well as investment bankers over the last forty years, in addition to creating amazing gains in efficiency and productivity. This trend is in full force, through both fast-growing and slow-growing economic conditions. The right combination of smart and simple sensors like ambient light and proximity sensors along with the optimal support devices such as instrumentation amplifiers and sensor amps, assures the industry of continuing innovation and productivity enhancement.

About the Author Tamara Schmitz is a Senior Principal Applications Engineer and Global Technical Training Coordinator at Intersil Corporation, where she has been employed since mid 2007. Tamara holds a BSEE and MSEE in electrical engineering and Ph.D. in RF CMOS Circuit Design from Stanford University. From August 1997 until August 2002 she was a lecturer in electrical engineering at Stanford; from August 2002 until August 2007, she served as assistant professor of electrical engineering at San Jose State University. Among her interests are traveling, woodworking, dog training, playing guitar and accordion, and following major league baseball/college football. She is always ready for the next adventure, whether it is an African safari or a new application circuit.■

Figure 2: Modern robotics systems featuring sophisticated multi axis arms are adding to factory productivity and safety. Simply picking up an object can require several sensors.

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