eeweb pulse - issue 4, 2011

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Dr. John D. CresslerNanoscale Transistors and

Integrated Circuits

Electrical Engineering Commun

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TABLE OF C ONTENTS

Dr. John D. Cressler 4KEN BYERS PROFESSOR, GEORGIA INSTITUTE OF TECHNOLOGYInterview with Dr. John D. Cressler, School of Electrical and Computer Engineering.

Silicon-Germanium in Space 7BY DR. JOHN D. CRESSLER

Key Switch Controllers Enhance Smart 11PhonesBY WALTER CHEN WITH MAXIM

The Future of 8-Bit Microcontrollers in 16In-Home Elderly CareBY STEVE DARROUGH WITH ZILOG

RTZ - Return to Zero Comic 18

Chen compares conventional and low-EMI key-scanning, and illustrates a major benefit of thelow-EMI method.

Microcontrollers will enable emerging technologies to play a pivotal role in elderly healthcare,allowing for prolonged independent living.

Georgia Tech-Led Project Pioneers Extreme-Environment Electronics for NASA.



INTERVIEW

Dr. John D. Cressler

Nanoscale Transistors andIntegrated Circuits

How did you get intoelectronics/engineering and

when did you start?

I had the great fortune as a juniorat Roswell high school to takeCalculus with Dr. Don Dorminy.Besides being a terrific teacher

with a flare for the dramatic, DocD helped me connect, for the firsttime really, the beautiful linkagebetween mathematics and physics.It resonated, and this turned out tobe a tipping point in my life. 1978.

After high school I attended GeorgiaTech, majoring in physics. I loved it.During my sophomore year I beganco-oping at IBM in the ResearchTriangle in North Carolina, workingin a small R&D group doing ...microelectronics. Interestinglyenough, microelectronics (read:all things transistor) turns out to be

a great blend of physics and EE. Iwas hooked! I decided that I would

stay a physics major, but take allof my electives in EE (admittedlynot the easy path, but it served me

very well), and over the next sevenquarters I alternated betweendoing transistor R&D at IBM andtaking classes in EE and physicsaimed at developing the neededbackground. My career was set.

When I graduated with my BS fromTech (1984), I took my dream job atIBM Research, in Yorktown Heights,NY, working on transistors and theiruse in novel types of electronicsystems. IBM sent me back formy PhD (and paid my way!) atColumbia University in New YorkCity. I finished in 1990. Two yearslater, on a whim really (read: anothertipping point), I took a night timeteaching job at a local university in

Danbury, Connecticut (Calculus

no less!), and literally from the veryfirst day I knew I wanted to be aprofessor. I get to teach, work withand help train bright young folks,and also continue my research. Best

job on the planet. I left IBM to jointhe EE faculty at Auburn Universityin 1992, and joined Georgia Tech in2002. The rest is history.

What are your favoritehardware tools that you use?

My team specializes in theunderstanding, design, andmeasurement of game-changingnovel nanoscale transistors,and integrated circuits frombuilt them, including silicon-germanium (SiGe) heterojunctionbipolar transistors (HBTs) (amouth full!). We can measurescattering parameters on such

devices to 67 GHz, tuned noiseparameters to 40 GHz, andtuned load-pull (distortion)characteristics up to 40 GHz.

All require very sophisticated(and expensive) instrumentation.In addition, we have severalspecialty instruments, one of

which enables us to measuretransistors and circuits runningoperating down to 4K, just

above absolute zero. We usedthis instrument to set the worldtransistor speed record inSiGe transistors a few yearsback. It was operating with anextrapolated maximum powergain frequency above 600 GHz at4.5K. This requires (clever) use ofliquid helium and a little luck!

Dr. John D. Cressler - Georgia Tech. School of Electrical and Computer Engineering



INTERVIEW

What are your favoritesoftware tools that you use?

To design our circuits we usethe Cadence Design Suitefor simulating, laying-out andchecking our circuit designs priorto fabrication. For understandingthe physics of our transistors weuse Synopsis TCAD tools forbuilding a virtual 3D transistor

within the computer, simulating itsphysics, and then comparing thoseresults to actual measurements totease out information on what isactually going on.

What is on your bookshelf?

For my personal reading, it isnovels all the way. Recent readsinclude A Visit from the GoodSquad, by Jennifer Egan, The History of Love, by NicoleKrauss, and Colum McCanns, Let the Great World Spin. All

were wonderful reads! Engineers

MUST read non-technical booksto be well rounded. I enjoy writingas well, and for those interested,

you might check out my mostrecent book (shameless plugalert!), Silicon Earth: Introductionto the Microelectronics and

Nanotechnology Revolution.It is intended to introduce non-specialists to the ins and outs ofmicro/nanotechnology. A fun read.

Check it out on my web site. Youmight also see my TED talk on thistopic (also on my website).

Do you have any tricks upyour sleeve?

I tell my students to trust theirintuition. Then back it up with

hard evidence. I also tell themto never discount data that lookscrazy or makes no sense at firstglance. Most stand ready to tosssuch data in the trash, but ourgreatest discoveries usually turnup by chasing crazy data down therabbit hole.

What has been your favoriteproject?

On the technical side, I think theNASA project described in therecent press release has beenmy favorite. We took some basicphysics (SiGe HBTs should

work well at extremely coldtemperatures and in a harshradiation environment), soldNASA on a vision to develop SiGetechnology for such extremeenvironments, and ran with it.

Weve had a ton of fun and thestory is just at the beginning. What

we are doing has the chance toinfluence a great many things

in the way space missions aredesigned and carried out. Thatsexciting! We presently have someof our designs riding on theInternational Space Station.

Okay, okayit

did indeed have a

protective plastic coverthat said DANGER,

DONT REMOVE on it.

I consider my principal vocationto be teaching, and I had a

truly gratifying experience thispast year. I always wanted tointroduce a course for non-ECEstudents that assumed nothingbut high school background,and yet would educate folksabout the many miracles beingcreated in microelectronics andnanotechnology. Miracles thatare changing the way our world

works. I wrote a book to go withit (see Silicon Earth above)and the course has really worked

very, very well. I do the technicalpiece (how transistors work,

where they came from), but alsodiscuss societal impact issues(e.g., are social media a goodthing?), and we do team widgetdeconstruction projects where

we pull apart ubiquitous piecesof technology and see how theyactually work (LCD TV, iPOD,GPS, etc.). A ton of fun!

Do you have any note-worthyengineering experiences?

Heres a fun one. Smoking aDevice. One of my favoritechildhood books was Hans andMargret Reys 1941 CuriousGeorge, about a cute littlemonkey named George whoalways seemed to get into trouble

just because he was overlycurious about things. Well, mynames not George, but on the

first week on my new co-op jobat IBM in Research Triangle Park,NC, way back when, I pulled aGeorge. Yep, a mighty-green, still-

wet-behind-the-ears, second yearundergraduate co-op student fromGeorgia Tech, having just beentrained to use a tungsten needleprobe to contact and measure
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INTERVIEW

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his first semiconductor device (aMOSFET), decided it would becool to see just how much voltage

his tiny little device could actuallyhandle. In those dark ages weused something called a ``curvetracer for such measurements;basically just a fancy variable

voltage/current source and meter.On the front of the curve tracer

was a switch that would allow oneto remove the current compliancelimit on such a measurement(okay, okay it did indeed havea protective plastic cover that said``DANGER, DONT REMOVEon it). Just for fun, I intentionallydefeated the complianceprotection and proceeded to rampup said voltage on my device. Icrossed the suspected breakdown

voltage and just kept on going.Imagine my shock when I smelled

something funny, glanced over atmy probe station, and saw a smallbut clearly visible mushroom cloud

of smoke rising from my device. Aghast, I raced to look into mymicroscope at the carnage, and tomy horror, all I saw were peeledback, melted tungsten probes(melting point = 6,192 F), andunderneath them, an ugly craterin the surface of my silicon wafer(melting point = 2,577 F) whichsaid MOSFET used to call home.

Alas, Mr. MOSFET was no more.SMOKED! Moral for George: Inthe absence of some mechanismto limit the current flow, breakdownin semiconductors will try VERYhard to reach infinite current. TheIR drop associated with this now

very large current will produce amassive temperature rise that that

will quickly grow to surface-of-the-

sun like temperatures! Not a goodthing. To all you budding deviceengineers you havent lived

until you have smoked your firstdevice! Give it a try!

What are you currentlyworking on?

For something technical, seefavorite project above. Howsthis for non-technical? I amactually working on my first novel,a love story set in mid-14th centuryMuslim Spain, in the AlhambraPalace in Granada. Fascinatingera. Im trying to bring it alive. I

just finished the first draft andam loving every minute of it. Staytuned!
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PROJECT

Silicon-Germanium in Space:Georgia Tech-Led Project Pioneers Extreme-

Environment Electronics for NASA

Afive-year project led by theGeorgia Institute of Technologyhas developed a novel approachto space electronics that couldchange how space vehicles andinstruments are designed. The newcapabilities are based on silicon-germanium (SiGe) technology,

which can produce electronics thatare highly resistant to both widetemperature variations and spaceradiation.

Titled SiGe Integrated Electronicsfor Extreme Environments, the$12 million, 63-month project wasfunded by the National Aeronauticsand Space Administration (NASA).In addition to Georgia Tech, the 11-member team included academicresearchers from the University

of Arkansas, Auburn University,University of Maryland, University

of Tennessee, and VanderbiltUniversity. Also involved in theproject were BAE Systems, BoeingCo., IBM Corp., Lynguent Inc., andNASAs Jet Propulsion Laboratory.

The teams overall task was todevelop an end-to-end solutionfor NASAa tested infrastructure

that includes everything neededto design and build extreme-environment electronics for spacemissions, said John Cressler, whois a Ken Byers Professor in GeorgiaTechs School of Electrical andComputer Engineering. Cresslerserved as principal investigator andoverall team leader for the project.

During the past five years, workdone under the project has resulted

in some 125 peer-reviewedpublications.

Unique Capabilities

SiGe alloys combine silicon, themost common microchip material,

with germanium, at nanoscaledimensions. The result is a robustmaterial that offers important gainsin toughness, speed, and flexibility.

That robustness is crucial tosilicon-germaniums ability tofunction in space without bulkyradiation shields or large, power-hungry temperature controldevices. Compared to conventionalapproaches, SiGe electronics canprovide major reductions in weight,size, complexity, power and cost,as well as increased reliability andadaptability.

Our team used a mature silicon-germanium technologyIBMs 0.5micron SiGe technologythat wasnot intended to withstand deep-space conditions, Cressler said.Without changing the compositionof the underlying silicon-germaniumtransistors, we leveraged SiGesnatural merits to develop newcircuit designs, as well as newapproaches to packaging the finalcircuits, to produce an electronic

system that could reliably withstandthe extreme conditions of space.

At the end of the project, theresearchers supplied NASA witha suite of modeling tools, circuitdesigns, packaging technologiesand system/subsystem designs,along with guidelines for qualifyingthose parts for use in space. In

By Dr. John D. Cressler

Image 1:Georgia Tech student researcher Troy England works in the laboratory

with a device containing silicon-germanium microchips, seen in his left hand.

(Photo: Gary Meek)



PROJECT

addition, the team furnished NASA with a functional prototype calleda silicon-germanium remoteelectronics unit (REU) 16-channelgeneral purpose sensor interface.

The device was fabricated usingsilicon-germanium microchips andhas been tested successfully insimulated space environments.

A New Paradigm

Andrew S. Keys, center chieftechnologist at the Marshall SpaceFlight Center and NASA programmanager, said the now completedproject has moved the task ofunderstanding and modelingsilicon-germanium technology toa point where NASA engineerscan start using it on actual vehicledesigns.

The silicon-germanium extremeenvironments team was verysuccessful in doing what it set outto do, Keys said. They advancedthe state-of-the-art in analog silicon-germanium technology for spaceusea crucial step in developing

a new paradigm leading to lighter weight and more capable spacevehicle designs.

Keys explained that, at best, mostelectronics conform to militaryspecifications, meaning theyfunction across a temperature rangeof negative 55 degrees Celsius to 125degrees Celsius. But electronics indeep space are typically exposed tofar greater temperature ranges, as

well as to damaging radiation. TheMoons surface cycles between 120degrees Celsius during the lunarday to negative 180 degrees Celsiusat night.

The silicon-germanium electronicsdeveloped by the extremeenvironments team has been shownto function reliably throughout that

entire 120 to negative 180 degreesCelsius range. It is also highlyresistant or immune to various typesof radiation.

The conventional approach toprotecting space electronics,developed in the 1960s, involvesbulky metal boxes that shielddevices from radiation andtemperature extremes, Keysexplained. Designers must placemost electronics in a protected,temperature controlled centrallocation and then connect them vialong and heavy cables to sensors orother external devices.

By eliminating the need for mostshielding and special cables,silicon-germanium technologyhelps reduce the single biggestproblem in space launches

weight. Moreover, robust SiGecircuits can be placed whereverdesigners want, which helpseliminate data errors caused by

impedance variations in lengthywiring schemes.

For instance, the Mars ExplorationRovers, which are no bigger than a

golf cart, use several kilometers ofcable that lead into a warm box,Keys said. If we can move mostof those electronics out to wherethe sensors are on the robotsextremities, that will reduce cabling,

weight, complexity, and energy usesignificantly.

A Collaborative Effort

NASA currently rates the new

SiGe electronics at a technologyreadiness level of six, which meansthe circuits have been integratedinto a subsystem and tested in arelevant environment. The next step,level seven, involves integratingthe SiGe circuits into a vehicle forspace flight testing. At level eight,a new technology is mature enoughto be integrated into a full mission

Image 2:Georgia Tech Professor John Cressler , with the help of a student

researcher, examines a functional prototype developed for NASA using silicon-

germanium microchips. (Photo: Gary Meek)



PROJECT

vehicle, and at level nine thetechnology is used by missions ona regular basis.

Successful collaboration wasan important part of the silicon-

germanium teams effectiveness,Keys said. He remarked that he hadnever seen such a diverse team

work together so well.

Professor Alan Mantooth, wholed a large University of Arkansascontingent involved in modelingand circuit-design tasks, agreed.He called the project the mostsuccessful collaboration that Ivebeen a part of.

Mantooth deemed the extreme-electronics project highly usefulin the education mission of theparticipating universities. He notedthat a total of 82 students from sixuniversities worked on the projectover five years.

Richard W. Berger, a BAE Systems

senior systems architect whocollaborated on the project, alsopraised the student contributions.

To be working both in analogand digital, miniaturizing, and

developing extreme-temperatureand radiation tolerance all at thesame timethats not what youdcall the average student designproject, Berger said.

Miniaturizing an

Architecture

BAE Systems contribution to theproject included providing thebasic architecture for the remoteelectronics unit (REU) sensorinterface prototype developedby the team. That architecturecame from a previous electronicsgenerationthe now cancelledLockheed Martin X-33 Spaceplaneinitially designed in the 1990s.

In the original X-33 design, Bergerexplained, each sensor interfaceused an assortment of sizeable

analog parts for the front-endsignal receiving section. Thatsection was supported by a digitalmicroprocessor, memory chips,and an optical bus interfaceall

housed in a protective five-poundbox.

The extreme environments teamtransformed the bulky X-33 designinto a miniaturized sensor interface,utilizing silicon germanium. Theresulting SiGe device weighsabout 200 grams and requires notemperature or radiation shielding.Large numbers of these robust,lightweight REU units could be

mounted on spacecraft or data-gathering devices close to sensors,reducing size, weight, power, andreliability issues.

Berger said that BAE Systemsis interested in manufacturing asensor interface device based onthe extreme environment teamsdiscoveries.

Other space-oriented companiesare also pursuing the new silicon-

germanium technology, Cresslersaid. NASA, he explained, wants theintellectual property barriers to thetechnology to be low so that it canbe used widely.

The idea is to make thisinfrastructure available to allinterested parties, he said.That way it could be used forany electronics assembly suchas an instrument, a spacecraft,

an orbital platform, lunar-surfaceapplications, Titan missionswherever it can be helpful. In fact,the process of defining such aNASA mission-insertion roadmap iscurrently in progress.

Image 3:This close-up image shows a remote electronics unit 16-channel

sensor interface, developed for NASA using silicon-germanium microchips by an

11-member team led by Georgia Tech. (Photo: Gary Meek)



Enhance Smart Phones

Key-SwitchControllers

Walter Chen

Senior Scientist,

Applications

T

he key pad of most smart phones employs oneof two key-scanning methods: conventional or

low-EMI. By describing and comparing thesemethods, the following discussion illustrates a majorbenefit of the low-EMI method it eliminates theneed for EMI filters. Estimates are then made of thecapacitive-loading allowance associated with externalESD-protection diodes. We conclude that the use ofa low-EMI key-scanning controller provides the bestperformance in smart phone applications.

The brain of a smart phone is the baseband (BB)controller, which contains a microprocessor and special-purpose signal-processing circuits. General purpose

input/output (GPIO) pins may be available to implementthe key-switching circuitry, but that depends on thecomplexity of the BB controller.

Special-purpose key-switch controller chips are usedin many of the recent smart cell phones. Such chipsare often used because not enough GPIO pins areavailable on the BB controller. This can happen when aBB controller designed for a feature phone is used for asmart phone as well, to avoid the cost of redevelopingthe system infrastructure. In other cases, a dedicated

controller chip is used to minimize the number ofwires between the BB controller and the key pad. This

approach applies especially for systems with a slide-outkey pad where the BB controller and the key pad arelocated on different PCBs or chassis. The key-switchcontroller usually connects to the BB controller via an(I^2)C or SPI interface [1].

You can implement a dedicated switch controller withan off-the-shelf GPIO chip, or a small microcontrollerusing the conventional key-scan method. Conventionalkey-scan methods are also used in a few dedicated,special-purpose key-switch controller chips. In thisarticle, a comparison of the conventional and low-

EMI methods of key scanning shows that the low-EMImethod eliminates the need for EMI filters.

Conventional Key-Scan Method

The conventional key-scan method (Figure 1) is used with BB controllers that include GPIO pins, and alsowith some dedicated key-switch controllers. Some GPIOpins are used as column-output ports to drive the switchmatrix, and other GPIO pins are used as row- input portsto detect the contact of switches. Usually, the system



FEATURED ARTICL E

applies no voltage to any key switch unless it is beingtouched. Once a key is pressed, the key controllerbegins a scan of all the keys. This scanning is carriedout by raising the column voltages one at a time, whilechecking (also one at a time) the input level of eachrow. An 88 switch matrix can be scanned in 64 clockcycles, and the clock frequency can range from a fewtens of kilohertz to a few megahertz. During a key scan,the column-output levels swing between logic low andlogic high, which is 1.8V to 3.3V depending on the keycontrollers power supply.

The Key at COL2 and ROW2

is pressed in this example

3.3VEnable COL0

COL0

V+ Open-0V Closed

Voltage Swings

COL1

COL2

Enable COL1

Enable COL2

ROW0 Detection

ROW1 Detection

ROW2 Detection

COL0

3.3VCOL1

3.3VCOL2

3.3VROW2

ROW1

ROW0

(a)

50

RS R1 R2

RL47 pF C1

VS

33 33

50+

(b)

50

RS R1

RLVS

33

50+

47 pF C1 47 pF C2

that flows through the rows as they are turned on one ata time. For this passive-scan technique, an 88 switchmatrix can be scanned in 64 clock cycles, because theflow of constant current is detected one column at atime. During the key scan, all column voltages are staticat 0.5V except the one with a key pressed, whose voltagedrops to nearly 0V during the time slot for scanning thecorresponding row port.

Each column port is driven by a constant-current sourceof about 20A. This amount of current flows through the

column and row ports for which a switch makes contact,but only for a short time interval. Power consumptionfor the passive-scan method can therefore be muchlower than that of the conventional approach, in whichthe voltage swings must drive capacitive and resistiveloads.

The Key at COL2 and ROW2

is pressed in this example

0.5V

0.5V

0.5V

0.5V

Enable COL0

Current Detection COL2



COL0

V+

-.36 - 0.65V Open



FEATURED ARTICL E

Frequency (Hz)

PSD(dBm/Hz)

0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5

x 106

-30

-35

-40

-45

-50

-55

-60

-65

-70

-75

-80

Conventional

Method

Passive-scan

Method

Figure 4: Simulated key scan PSD levels. The blue curve

represents the conventional method, and the green curve

represents the passive-scan method used by Maxim

Mode Normal& Holdoff

SourceCh1Type Edge

A TriggerSlope

CouplingDC

Slope

2

1

T

T

Level360 mV

Ch1 1.00V Ch2 500mV M20.0ms A Ch1 360mV

73.3200ms

TekStop T

Figure 5: Simulated key-scan PSD levels. Channel 1

shows the column port, and channel 2 shows the row

port voltages for the MAX7359 key-switch controller

Electromagnetic Emission Comparison

For a 1.8V power supply, a voltage swing of 0.5Vinstead of the whole rail can provide a reduction inelectromagnetic emission of more than 11dB. The less-

frequent swings of the low-EMI method also help toreduce the level of electromagnetic emissions. Figure4 shows the simulated power-spectrum-density (PSD)levels for the conventional and low-EMI methods of keyscanning. Tests assume a clock frequency of 1MHz, asupply voltage of 1.8V, and rise/fall times of 0.2s. Theblue curve represents the conventional method, and thegreen curve shows Maxims passive-scan method. Theresults show that the PSD level for the low-EMI methodis 15dB lower. In fact, the low-EMI method produceselectromagnetic emissions about 15dB lower than those

of the conventional method. This reduction lets youavoid the use of EMI filters.

The dark blue trace (channel 1) in Figure 5 showsthe column port and the light blue trace (channel 2)displays the row port voltages of a MAX7359 key-switchcontroller. A key that crosses these column and row

ports is pressed at around 26ms. The key controllerthen wakes up with a delay of ~2ms, applies a currentsource to the column port (producing a voltage of about0.5V), and starts scanning. It scans twice at the chosendebounce time before deciding whether a key is stilldepressed, or has been released. For a pair of adjacentscanning pulses, the one on the left is the original scanand the one on the right is the secondary debouncescan.

ESD Protection and Capacitance Loading

Allowance

Because ports connected to the key pads are exposed toESD (ElectroStatic Discharge), they need to be protected,sometimes up to 15kV. The built-in ESD protectionfor certain key-scan controllers is 2kV (MAX73447,MAX7348, MAX7349, MAX7359), and for the MAX7360 is8kV. External ESD diodes in conjunction with internalcircuitry usually provides adequate protection, but thediodes add capacitive loading to those ports. Althoughdistinctive key pressed and key released codesenable the system to recognize multiple simultaneouskey presses and their sequences, this capacitive loadingis multiplied on the column and row ports involved. Eachcolumn port is driven by a constant-current source of20A 30%, and each row port is pulled to ground byapplying a positive pulse at the gate of the row portsoutput transistor. The system detects a key-press action

when the closure of a key switch pulls a column port toground while the row port is at ground level.

While a positive pulse is applied to the gate of therow ports output transistor (and shortly thereafter) theswitchs closing point discharges and then charges.Right after the positive pulse, the closing point quicklydischarges to zero from 0.5V. After the positive pulse



FEATURED ARTICL E

approach applies only when the pressed keys share thesame column port.

The excessive capacitance problem can also be avoidedby reassigning a frequently pressed key in a multiple-

key-pressing action (such as the shift key) to a separatecolumn port, where only the capacitances from onecolumn port and one row port are considered. For thecase of a single key to be pressed in each column port,the capacitance allowed at each port can be increasedto

With a port capacitance of 20pF, the resulting external

capacitance is therefore 162pF.We have examined the merits of using a dedicated, low-EMI key-switch controller for smart phones, and foundthat the EMI filters required in the conventional approachcan be avoided in the low-EMI approach. Equallyimportant, the use of a low-EMI key-switch controllerin many smart phones can improve the overall systemdesign and cost. Note that the estimated capacitiveloading allowances are reasonable for most cell-phonekeypad hardware, but you should avoid the use of ESDdevices that impose heavy capacitive loading.

[1] SPI is a trademark of Motorola, Inc.

About the Author

Dr. Walter Y. Chen has been with Maxim IntegratedProducts since 2000 specializing in Mixed SignalProcessing. His prior career experiences include thoseat Motorola, TI, and Bell Labs. He has made contributionsto DSL and Home Networking technologies. He holds aPhD degree from Polytechnic University and a MSEE

from CalTech.

disappears, the closing point charges back to 0.5V,based on the formula

where C is the total capacitance at the switch closingpoint. As an example, for C = 30pF it takes

The scan period is

In an application circuit, the charging process isaffected by the capacitance of column and row portsincluding those with attached ESD-protection diodes.

When the charging time is longer than the scan period,a false key pressed detection can occur. The falselydetected key can be the one whose row scan followsthe pressed key on the same column.

To limit the charging time to less than 13s while givingthe circuit about 2.625s to detect the key pressedstate (while also considering the constant-current-source tolerance of 30%), the total capacitance shouldbe less than 364pF:

Assuming that a shift key and a regular key are pressedsimultaneously, the capacitance at each port, including

those with an ESD-protection diode attached, should beless than:

182 pFCC

2port

total= =

13 10 3646

# # =-

..C

VI t

1

0 5

120 10 0 7total c

6# #= =

-

121 pFCC

3port

total= =

VC

I tC

t1 1

20 10c

6#= = -

This calculation includes the capacitances of two rowports and a column port. If the port capacitance is 20pFthe allowed external capacitance is 101pF, but this

.t

V C

20 10 20 10

0 5 30 10

2

15 106 6

712

# #

# # #= = =

- -

--#

. .s to reach V0 75 0 5n=

~ .64 10

1

15 6253#=

sn

pF
http://bit.ly/l6u6Cx



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What is the right technology solution for a hugeglobal need? Statistically speaking, our worldfaces a looming crisis that, while it doesnt hit

the headlines often, will eventually affect every singleperson on our planet, and in crucial ways. The crisis?Our aging population and an avalanche of need thatcould likely fall upon the shoulders of us all.

Not enough money, nowhere near enough elderly carefacilities, and a changing world that leaves many elderlypeople with nowhere to turn. These are the symptomsof a population of adults over age 65 that is growing at

three times the rate of the population of family membersthat are available to care for them. Observing the growthrate of the worlds fast-aging population suggests thatthose who experience middle age in the year 2050

will be three times more likely than they are now to beresponsible for the care of many of the projected twobillion-plus elderly. These are stark numbers, and yetthese numbers are increasing at an alarming rate; theysuggest that many elderly will require some level of

assistance but have no one around to help.

As we get older, several natural tendencies may occur:Folks are not as active as they once were; they may oftenbe sedentary, sitting and reading or watching televisionmore than they did before. These are not bad things,certainly, but weve already learned that prolongedperiods without physical movement can result ininsufficient exercise, which can subsequently lead toother types of health problems. Often, people becomemore forgetful as they age, and even forgetting simplethings such as taking the medicine, feeding the cat, or

even scheduling a grocery delivery can ultimately leadto a lack of independence.

In addition, its not unrealistic to predict that a largepercentage of people will reach a point in which they

will prefer to age in place. People who have workedall of their lives to own their home simply want to stayin it as long as possible. However, they will need a littlehelp to remain independent help that can also lightenthe demand for costly services. Thats where new



TECHNICAL ARTICLE

emerging technologies can play a meaningful role.Many people, as they age, are facing challenges thatare completely new to them, and they will simply needa little technological help ensure that their healthcareneeds are met.

So just what is the solution that can not only assistoverburdened caregivers, but even allow the aged toremain longer in their own homes and stay independentat managing their own healthcare needs?

As we get older, several

natural tendencies may occur:

Folks are not as active as they

once were; they may often besedentary, sitting and reading

or watching television more

than they did before.

Imagine a smart 8-bit microcontroller that can enablepeople to live independently, for much longer, and

without requiring additional support from the healthcaresystems that are currently in place. Indeed, an MCU-controlled sensor installed in an aging parents home

could detect patterns which, when they vary fromthe norm, could be set to alert a remote healthcareservice to respond and/or intervene when needed.

While privacy could be a concern in such a situation,safeguards could be built into such a monitoring systemfor assisted living in order to allow people to stay in theirown homes longer.

Isnt that a far better alternative than being uprootedand moved to a care facility where you may not feel ascomfortable?

Lets look at a set of microcontroller-based sensors which could cover a gamut of situational needs forfolks desiring to continue living in their own homes. Forexample, the safe monitoring process mentioned abovecould allow a caregiver to check in and observesimple lifestyle patterns that would help to makedeterminations and suggestions for ensuring a personsquality of life.

Having a smart, scalable independent living network inplace can assist with many everyday tasks by providingreminders or warnings which can inform a person that,for example, the tea on the stove is boiling over. Getting alittle reminder about that doctors appointment scheduled

for this afternoon can lead to better personal healthcaremanagement. Many of these technical helpers merelyrequire a microcontroller to process information basedon the function(s) for which they are designed. By design,these technical helpers can be interconnected to providea platform solution that can assist elderly living, with theend result being a persons self-determined path to stayindependent far longer.

Tomorrows need is already on us today, yet 8-bitmicrocontrollers will play a far larger role than manynow imagine. The actions we take today will be the ones

we ourselves will live with tomorrow, through creativesolutions that leverage smart MCUs. As a result, we willprotect not only our aging loved ones who can then enjoya better quality of life, but we will also creatively leveragethose wonderful microcontrollers so that we, like ourparents, can live more independently in the future.

What is the right technology solution for a huge globalneed? Statistically speaking, our world faces a loomingcrisis that while it doesnt hit the headlines often willeventually affect every single person on our planet,

and affect us in crucial ways. The crisis? Our agingpopulation and an avalanche of need that could likelyfall upon the shoulders of us all.

About the Author

Steve Darrough is Vice President of Marketing at IXYS-Zilog. Steve joined Zilog in 2008. Steve possessesmore than twenty years of technical engineering andmarketing management experience, leading brandingand marketing programs. Prior to coming onboard withZilog, Steve held marketing management and technicalengineering roles at Intel Corporations for over 14 years

where he had several teams driving new technologiesdirectly relating to the current products initiatives. Histeams drove worldwide programs in evangelizing newtechnologies and accelerate adoption. Steve has aMarketing Degree from the University of Oklahoma.



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