eeweb pulse - volume 4

PULSE EEWeb.comIssue 4

July 26, 2011

Dr. John D. Cressler Nanoscale Transistors and Integrated Circuits

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TABLE O

F CO

NTEN

TSTABLE OF CONTENTS

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 11Phones BY WALTER CHEN WITH MAXIM

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

RTZ - Return to Zero Comic 18

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


INTERVIEWFEA

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Dr. John D. Cressler Nanoscale Transistors and Integrated Circuits

How did you get into electronics/engineering and when did you start?

I had the great fortune as a junior at Roswell high school to take Calculus with Dr. Don Dorminy. Besides being a terrific teacher with a flare for the dramatic, Doc D helped me connect, for the first time really, the beautiful linkage between mathematics and physics. It resonated, and this turned out to be a tipping point in my life. 1978. After high school I attended Georgia Tech, majoring in physics. I loved it. During my sophomore year I began co-oping at IBM in the Research Triangle in North Carolina, working in a small R&D group doing ... microelectronics. Interestingly enough, microelectronics (read: all things transistor) turns out to be

a great blend of physics and EE. I was hooked! I decided that I would stay a physics major, but take all of my electives in EE (admittedly not the easy path, but it served me very well), and over the next seven quarters I alternated between doing transistor R&D at IBM and taking classes in EE and physics aimed at developing the needed background. My career was set. When I graduated with my BS from Tech (1984), I took my dream job at IBM Research, in Yorktown Heights, NY, working on transistors and their use in novel types of electronic systems. IBM sent me back for my PhD (and paid my way!) at Columbia University in New York City. I finished in 1990. Two years later, on a whim really (read: another tipping point), I took a night time teaching job at a local university in

Danbury, Connecticut (Calculus no less!), and literally from the very first day I knew I wanted to be a professor. I get to teach, work with and help train bright young folks, and also continue my research. Best job on the planet. I left IBM to join the EE faculty at Auburn University in 1992, and joined Georgia Tech in 2002. The rest is history.

What are your favorite hardware tools that you use?

My team specializes in the understanding, design, and measurement of game-changing novel nanoscale transistors, and integrated circuits from built them, including silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) (a mouth full!). We can measure scattering parameters on such devices to 67 GHz, tuned noise parameters to 40 GHz, and tuned load-pull (distortion) characteristics up to 40 GHz. All require very sophisticated (and expensive) instrumentation. In addition, we have several specialty instruments, one of which enables us to measure transistors and circuits running operating down to 4K, just above absolute zero. We used this instrument to set the world transistor speed record in SiGe transistors a few years back. It was operating with an extrapolated maximum power gain frequency above 600 GHz at 4.5K. This requires (clever) use of liquid helium – and a little luck!

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


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What are your favorite software tools that you use?

To design our circuits we use the Cadence Design Suite for simulating, laying-out and checking our circuit designs prior to fabrication. For understanding the physics of our transistors we use Synopsis TCAD tools for building a virtual 3D transistor within the computer, simulating its physics, and then comparing those results to actual measurements to tease out information on what is actually going on.

What is on your bookshelf?

For my personal reading, it is novels all the way. Recent reads include “A Visit from the Good Squad,” by Jennifer Egan, “The History of Love,” by Nicole Krauss, and Colum McCann’s, “Let the Great World Spin.” All were wonderful reads! Engineers MUST read non-technical books to be well rounded. I enjoy writing as well, and for those interested, you might check out my most recent book (shameless plug alert!), “Silicon Earth: Introduction to the Microelectronics and Nanotechnology Revolution.” It is intended to introduce non-specialists to the in’s and out’s of micro/nanotechnology. A fun read. Check it out on my web site. You might also see my TED talk on this topic (also on my website).

Do you have any tricks up your sleeve?

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

hard evidence. I also tell them to never discount data that looks crazy or makes no sense at first glance. Most stand ready to toss such data in the trash, but our greatest discoveries usually turn up by chasing crazy data down the rabbit hole.

What has been your favorite project?

On the technical side, I think the NASA project described in the recent press release has been my favorite. We took some basic physics (SiGe HBTs should work well at extremely cold temperatures and in a harsh radiation environment), sold NASA on a vision to develop SiGe technology for such “extreme environments,” and ran with it. We’ve had a ton of fun and the story is just at the beginning. What we are doing has the chance to influence a great many things in the way space missions are designed and carried out. That’s exciting! We presently have some of our designs riding on the International Space Station.

Okay, okay—it did indeed have a

protective plastic cover that said “DANGER,

DON’T REMOVE” on it.

I consider my principal vocation to be teaching, and I had a

truly gratifying experience this past year. I always wanted to introduce a course for non-ECE students that assumed nothing but high school background, and yet would educate folks about the many miracles being created in microelectronics and nanotechnology. Miracles that are changing the way our world works. I wrote a book to go with it (see “Silicon Earth” above) and the course has really worked very, very well. I do the technical piece (how transistors work, where they came from), but also discuss societal impact issues (e.g., are social media a good thing?), and we do team “widget deconstruction” projects where we pull apart ubiquitous pieces of technology and see how they actually work (LCD TV, iPOD, GPS, etc.). A ton of fun!

Do you have any note-worthy engineering experiences?

Here’s a fun one. “Smoking a Device.” One of my favorite childhood books was Hans and Margret Rey’s 1941 “Curious George,” about a cute little monkey named George who always seemed to get into trouble just because he was overly curious about things. Well, my name’s not George, but on the first week on my new co-op job at IBM in Research Triangle Park, NC, way back when, I pulled a George. Yep, a mighty-green, still-wet-behind-the-ears, second year undergraduate co-op student from Georgia Tech, having just been trained to use a tungsten needle probe to contact and measure


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his first semiconductor device (a MOSFET), decided it would be cool to see just how much voltage his tiny little device could actually handle. In those dark ages we used something called a ``curve tracer’‘ 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 one to remove the current compliance limit on such a measurement (okay, okay — it did indeed have a protective plastic cover that said ``DANGER, DON’T REMOVE’‘ on it). Just for fun, I intentionally defeated the compliance protection and proceeded to ramp up said voltage on my device. I crossed the suspected breakdown voltage and just kept on going. Imagine my shock when I smelled

something funny, glanced over at my probe station, and saw a small but clearly visible mushroom cloud of smoke rising from my device. Aghast, I raced to look into my microscope at the carnage, and to my horror, all I saw were peeled back, melted tungsten probes (melting point = 6,192 F), and underneath them, an ugly crater in the surface of my silicon wafer (melting point = 2,577 F) which said MOSFET used to call home. Alas, Mr. MOSFET was no more. SMOKED! Moral for George: In the absence of some mechanism to limit the current flow, breakdown in semiconductors will try VERY hard to reach infinite current. The IR drop associated with this now very large current will produce a massive temperature rise that that will quickly grow to surface-of-the-

sun like temperatures! Not a good thing. To all you budding device engineers — you haven’t lived until you have smoked your first device! Give it a try!

What are you currently working on?

For something technical, see “favorite project” above. How’s this for non-technical? I am actually working on my first novel, a love story set in mid-14th century Muslim Spain, in the Alhambra Palace in Granada. Fascinating era. I’m trying to bring it alive. I just finished the first draft and am loving every minute of it. Stay tuned! ■

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Silicon-Germanium in Space: Georgia Tech-Led Project Pioneers Extreme-Environment Electronics for NASA

A five-year project led by the Georgia Institute of Technology

has developed a novel approach to space electronics that could change how space vehicles and instruments are designed. The new capabilities are based on silicon-germanium (SiGe) technology, which can produce electronics that are highly resistant to both wide temperature variations and space radiation.

Titled “SiGe Integrated Electronics for Extreme Environments,” the $12 million, 63-month project was funded by the National Aeronautics and Space Administration (NASA). In addition to Georgia Tech, the 11-member team included academic researchers from the University of Arkansas, Auburn University, University of Maryland, University

of Tennessee, and Vanderbilt University. Also involved in the project were BAE Systems, Boeing Co., IBM Corp., Lynguent Inc., and NASA’s Jet Propulsion Laboratory.

“The team’s overall task was to develop an end-to-end solution for NASA—a tested infrastructure that includes everything needed to design and build extreme-environment electronics for space missions,” said John Cressler, who is a Ken Byers Professor in Georgia Tech’s School of Electrical and Computer Engineering. Cressler served as principal investigator and overall team leader for the project.

During the past five years, work done under the project has resulted in some 125 peer-reviewed publications.

Unique Capabilities

SiGe alloys combine silicon, the most common microchip material, with germanium, at nanoscale dimensions. The result is a robust material that offers important gains in toughness, speed, and flexibility.

That robustness is crucial to silicon-germanium’s ability to function in space without bulky radiation shields or large, power-hungry temperature control devices. Compared to conventional approaches, SiGe electronics can provide major reductions in weight, size, complexity, power and cost, as well as increased reliability and adaptability.

“Our team used a mature silicon-germanium technology—IBM’s 0.5 micron SiGe technology—that was not intended to withstand deep-space conditions,” Cressler said. “Without changing the composition of the underlying silicon-germanium transistors, we leveraged SiGe’s natural merits to develop new circuit designs, as well as new approaches to packaging the final circuits, to produce an electronic system that could reliably withstand the extreme conditions of space.”

At the end of the project, the researchers supplied NASA with a suite of modeling tools, circuit designs, packaging technologies and system/subsystem designs, along with guidelines for qualifying those 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)


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addition, the team furnished NASA with a functional prototype called a silicon-germanium remote electronics unit (REU) 16-channel general purpose sensor interface. The device was fabricated using silicon-germanium microchips and has been tested successfully in simulated space environments.

A New Paradigm

Andrew S. Keys, center chief technologist at the Marshall Space Flight Center and NASA program manager, said the now completed project has moved the task of understanding and modeling silicon-germanium technology to a point where NASA engineers can start using it on actual vehicle designs.

“The silicon-germanium extreme environments team was very successful in doing what it set out to do,” Keys said. “They advanced the state-of-the-art in analog silicon-germanium technology for space use—a crucial step in developing a new paradigm leading to lighter weight and more capable space vehicle designs.”

Keys explained that, at best, most electronics conform to military specifications, meaning they function across a temperature range of negative 55 degrees Celsius to 125 degrees Celsius. But electronics in deep space are typically exposed to far greater temperature ranges, as well as to damaging radiation. The Moon’s surface cycles between 120 degrees Celsius during the lunar day to negative 180 degrees Celsius at night.

The silicon-germanium electronics developed by the extreme environments team has been shown to function reliably throughout that

entire 120 to negative 180 degrees Celsius range. It is also highly resistant or immune to various types of radiation.

The conventional approach to protecting space electronics, developed in the 1960s, involves bulky metal boxes that shield devices from radiation and temperature extremes, Keys explained. Designers must place most electronics in a protected, temperature controlled central location and then connect them via long and heavy cables to sensors or other external devices.

By eliminating the need for most shielding and special cables, silicon-germanium technology helps reduce the single biggest problem in space launches—weight. Moreover, robust SiGe circuits can be placed wherever designers want, which helps eliminate data errors caused by

impedance variations in lengthy wiring schemes.

“For instance, the Mars Exploration Rovers, which are no bigger than a golf cart, use several kilometers of cable that lead into a warm box,” Keys said. “If we can move most of those electronics out to where the sensors are on the robot’s extremities, that will reduce cabling, weight, complexity, and energy use significantly.”

A Collaborative Effort

NASA currently rates the new SiGe electronics at a technology readiness level of six, which means the circuits have been integrated into a subsystem and tested in a relevant environment. The next step, level seven, involves integrating the SiGe circuits into a vehicle for space flight testing. At level eight, a new technology is mature enough to 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)


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vehicle, and at level nine the technology is used by missions on a regular basis.

Successful collaboration was an important part of the silicon-germanium team’s effectiveness, Keys said. He remarked that he had “never seen such a diverse team work together so well.”

Professor Alan Mantooth, who led a large University of Arkansas contingent involved in modeling and circuit-design tasks, agreed. He called the project “the most successful collaboration that I’ve been a part of.”

Mantooth deemed the extreme-electronics project highly useful in the education mission of the participating universities. He noted that a total of 82 students from six universities worked on the project over five years.

Richard W. Berger, a BAE Systems

senior systems architect who collaborated on the project, also praised the student contributions.

“To be working both in analog and digital, miniaturizing, and developing extreme-temperature and radiation tolerance all at the same time—that’s not what you’d call the average student design project,” Berger said.

Miniaturizing an Architecture

BAE Systems’ contribution to the project included providing the basic architecture for the remote electronics unit (REU) sensor interface prototype developed by the team. That architecture came from a previous electronics generation—the now cancelled Lockheed Martin X-33 Spaceplane initially designed in the 1990s.

In the original X-33 design, Berger explained, each sensor interface used an assortment of sizeable

analog parts for the front-end signal receiving section. That section was supported by a digital microprocessor, memory chips, and an optical bus interface—all housed in a protective five-pound box.

The extreme environments team transformed the bulky X-33 design into a miniaturized sensor interface, utilizing silicon germanium. The resulting SiGe device weighs about 200 grams and requires no temperature 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, and reliability issues.

Berger said that BAE Systems is interested in manufacturing a sensor interface device based on the extreme environment team’s discoveries.

Other space-oriented companies are also pursuing the new silicon-germanium technology, Cressler said. NASA, he explained, wants the intellectual property barriers to the technology to be low so that it can be used widely.

“The idea is to make this infrastructure available to all interested parties,” he said. “That way it could be used for any electronics assembly such as an instrument, a spacecraft, an orbital platform, lunar-surface applications, Titan missions—wherever it can be helpful. In fact, the process of defining such a NASA mission-insertion roadmap is currently 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 ChenSenior Scientist,

Applications

The key pad of most smart phones employs one of two key-scanning methods: conventional or low-EMI. By describing and comparing these

methods, the following discussion illustrates a major benefit of the low-EMI method— it eliminates the need for EMI filters. Estimates are then made of the capacitive-loading allowance associated with external ESD-protection diodes. We conclude that the use of a low-EMI key-scanning controller provides the best performance 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 implement the key-switching circuitry, but that depends on the complexity of the BB controller.

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

controller chip is used to minimize the number of wires between the BB controller and the key pad. This approach applies especially for systems with a slide-out key pad – where the BB controller and the key pad are located on different PCBs or chassis. The key-switch controller usually connects to the BB controller via an (I^2)C or SPI™ interface [1].

You can implement a dedicated switch controller with an off-the-shelf GPIO chip, or a small microcontroller using the conventional key-scan method. Conventional key-scan methods are also used in a few dedicated, special-purpose key-switch controller chips. In this article, a comparison of the conventional and low-EMI methods of key scanning shows that the low-EMI method 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 also with some dedicated key-switch controllers. Some GPIO pins are used as column-output ports to drive the switch matrix, and other GPIO pins are used as row- input ports to detect the contact of switches. Usually, the system


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applies no voltage to any key switch unless it is being touched. Once a key is pressed, the key controller begins a scan of all the keys. This scanning is carried out by raising the column voltages one at a time, while checking (also one at a time) the input level of each row. An 8×8 switch matrix can be scanned in 64 clock cycles, and the clock frequency can range from a few tens of kilohertz to a few megahertz. During a key scan, the column-output levels swing between logic low and logic high, which is 1.8V to 3.3V depending on the key controller’s power supply.

The Key at COL2 and ROW2is 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)

50Ω

RS R1 R2

RL47 pF C1VS

33Ω 33Ω50Ω

+–

(b)

50Ω

RS R1

RLVS

33Ω50Ω

+– 47 pF C1 47 pF C2

that flows through the rows as they are turned on one at a time. For this passive-scan technique, an 8×8 switch matrix can be scanned in 64 clock cycles, because the flow of constant current is detected one column at a time. During the key scan, all column voltages are static at 0.5V except the one with a key pressed, whose voltage drops to nearly 0V during the time slot for scanning the corresponding row port.

Each column port is driven by a constant-current source of about 20μA. 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 consumption for the passive-scan method can therefore be much lower than that of the conventional approach, in which the voltage swings must drive capacitive and resistive loads.

The Key at COL2 and ROW2is pressed in this example

0.5V

0.5V

0.5V

0.5V

Enable COL0

Current Detection COL2Current Detection COL1Current Detection COL0

COL0

V+

-.36 - 0.65V Open<0.15V Closed

20µA

+/-

20%

Static Voltage

Key Pressed Key Released

COL1

COL2

Enable COL1

Enable COL2

Enable ROW0

Enable ROW1

Enable ROW2

COL0

COL1

COL2

ROW2

ROW1

ROW0

Figure 1: The conventional key-scan method

Figure 2: Basic EMI filter structures

Figure 3: Maxim’s low-EMI key scan method

Because of sudden rises and falls in the column-scanning signals, corresponding electromagnetic emissions can affect the qualification of EMI tests, especially when long wires extend from the key pad to the BB controller’s GPIO pins. EMI filters are usually required on these column ports to minimize the effects of electromagnetic emission. An EMI filter can be a first-order RC or a second-order CRC lowpass filter (Figure 2a-2b). Such filters are available in small TDFN or CSP packages, or they can be implemented using discrete passive components. But of course, any EMI filter adds component cost and occupies board space.

Low-EMI (passive scan) Method

Certain key-switch controllers (MAX7347-49, MAX7359, MAX7360) use a passive-scan technique in which the switch contacts are detected by sensing currents that flow when the switch matrix is driven by current sources (Figure 3). Once a key is pressed, the key controller starts to scan all keys. The scanning is carried out by applying constant-current sources to all column outputs (with port-output voltages of about 0.5V) while sensing the current


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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

ConventionalMethod

Passive-scanMethod

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

TLevel

360 mV

Ch1 1.00V Ch2 500mV M20.0ms A Ch1 360mV73.3200ms

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 0.5V instead of the whole rail can provide a reduction in electromagnetic emission of more than 11dB. The less-frequent swings of the low-EMI method also help to reduce the level of electromagnetic emissions. Figure 4 shows the simulated power-spectrum-density (PSD) levels for the conventional and low-EMI methods of key scanning. Tests assume a clock frequency of 1MHz, a supply voltage of 1.8V, and rise/fall times of 0.2μs. The blue curve represents the conventional method, and the green curve shows Maxim’s passive-scan method. The results show that the PSD level for the low-EMI method is 15dB lower. In fact, the low-EMI method produces electromagnetic emissions about 15dB lower than those of the conventional method. This reduction lets you avoid the use of EMI filters.

The dark blue trace (channel 1) in Figure 5 shows the column port and the light blue trace (channel 2) displays the row port voltages of a MAX7359 key-switch controller. A key that crosses these column and row ports is pressed at around 26ms. The key controller then wakes up with a delay of ~2ms, applies a current source to the column port (producing a voltage of about 0.5V), and starts scanning. It scans twice at the chosen debounce time before deciding whether a key is still depressed, or has been released. For a pair of adjacent scanning pulses, the one on the left is the original scan and the one on the right is the secondary debounce scan.

ESD Protection and Capacitance Loading Allowance

Because ports connected to the key pads are exposed to ESD (ElectroStatic Discharge), they need to be protected, sometimes up to 15kV. The built-in ESD protection for certain key-scan controllers is ±2kV (MAX73447, MAX7348, MAX7349, MAX7359), and for the MAX7360 is ±8kV. External ESD diodes in conjunction with internal circuitry usually provides adequate protection, but the diodes add capacitive loading to those ports. Although distinctive “key pressed” and “key released” codes enable the system to recognize multiple simultaneous key presses and their sequences, this capacitive loading is multiplied on the column and row ports involved. Each column port is driven by a constant-current source of 20μA ±30%, and each row port is pulled to ground by applying a positive pulse at the gate of the row port’s output transistor. The system detects a key-press action when the closure of a key switch pulls a column port to ground while the row port is at ground level.

While a positive pulse is applied to the gate of the row port’s output transistor (and shortly thereafter) the switch’s closing point discharges and then charges. Right after the positive pulse, the closing point quickly discharges to zero from 0.5V. After the positive pulse


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

The excessive capacitance problem can also be avoided by reassigning a frequently pressed key in a multiple-key-pressing action (such as the shift key) to a separate column port, where only the capacitances from one column port and one row port are considered. For the case of a single key to be pressed in each column port, the capacitance allowed at each port can be increased to

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 found that the EMI filters required in the conventional approach can be avoided in the low-EMI approach. Equally important, the use of a low-EMI key-switch controller in many smart phones can improve the overall system design and cost. Note that the estimated capacitive loading allowances are reasonable for most cell-phone keypad hardware, but you should avoid the use of ESD devices that impose heavy capacitive loading.

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

About the Author

Dr. Walter Y. Chen has been with Maxim Integrated Products since 2000 specializing in Mixed Signal Processing. His prior career experiences include those at Motorola, TI, and Bell Labs. He has made contributions to DSL and Home Networking technologies. He holds a PhD 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 closing point. As an example, for C = 30pF it takes

The scan period is

In an application circuit, the charging process is affected by the capacitance of column and row ports including those with attached ESD-protection diodes. When the charging time is longer than the scan period, a false “key pressed” detection can occur. The falsely detected key can be the one whose row scan follows the pressed key on the same column.

To limit the charging time to less than 13μs while giving the circuit about 2.625μs to detect the “key pressed” state (while also considering the constant-current-source tolerance of 30%), the total capacitance should be less than 364pF:

Assuming that a shift key and a regular key are pressed simultaneously, the capacitance at each port, including those with an ESD-protection diode attached, should be less than:

182 pFCC2porttotal= =

..C

VI t F

10 51

20 10 0 7 13 10 364total c6 6# # # # t= = =- -

..C

VI t F

10 51

20 10 0 7 13 10 364total c6 6# # # # t= = =- -


VCI t

Ct

1 120 10

c6#= = -

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

.. .s to reach Vt

V C20 10 20 10

0 5 30 102

15 100 75 0 56 6

712

# ## # #

n= = = =- -

--#

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V C20 10 20 10

0 5 30 102

15 100 75 0 56 6

712

# ## # #

n= = = =- -

--#

~ . s64 10

115 6253#

n=.. .s to reach Vt

V C20 10 20 10

0 5 30 102

15 100 75 0 56 6

712

# ## # #

n= = = =- -

--#



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What is the right technology solution for a huge global need? Statistically speaking, our world faces a looming crisis that, while it doesn’t hit

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

Not enough money, nowhere near enough elderly care facilities, and a changing world that leaves many elderly people with nowhere to turn. These are the symptoms of a population of adults over age 65 that is growing at three times the rate of the population of family members that are available to care for them. Observing the growth rate of the world’s fast-aging population suggests that those who experience middle age in the year 2050 will be three times more likely than they are now to be responsible for the care of many of the projected two billion-plus elderly. These are stark numbers, and yet these numbers are increasing at an alarming rate; they suggest 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 often be sedentary, sitting and reading or watching television more than they did before. These are not bad things, certainly, but we’ve already learned that prolonged periods without physical movement can result in insufficient exercise, which can subsequently lead to other types of health problems. Often, people become more forgetful as they age, and even forgetting simple things such as taking the medicine, feeding the cat, or even scheduling a grocery delivery can ultimately lead to a lack of independence.

In addition, it’s not unrealistic to predict that a large percentage of people will reach a point in which they will prefer to “age in place.” People who have worked all of their lives to own their home simply want to stay in it as long as possible. However, they will need a little help to remain independent – help that can also lighten the demand for costly services. That’s where new


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

So just what is the solution that can not only assist overburdened caregivers, but even allow the aged to remain longer in their own homes and stay independent at 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 be sedentary, sitting and reading

or watching television more than they did before.

Imagine a smart 8-bit microcontroller that can enable people to live independently, for much longer, and without requiring additional support from the healthcare systems that are currently in place. Indeed, an MCU-controlled sensor installed in an aging parent’s home could detect patterns which, when they vary from the norm, could be set to alert a remote healthcare service 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 system for assisted living in order to allow people to stay in their own homes longer.

Isn’t that a far better alternative than being uprooted and moved to a care facility where you may not feel as comfortable?

Let’s look at a set of microcontroller-based sensors which could cover a gamut of situational needs for folks desiring to continue living in their own homes. For example, the safe monitoring process mentioned above could allow a caregiver to “check in” and observe simple lifestyle patterns that would help to make determinations and suggestions for ensuring a person’s quality of life.

Having a smart, scalable “independent living network” in place can assist with many everyday tasks by providing reminders or warnings which can inform a person that, for example, the tea on the stove is boiling over. Getting a little reminder about that doctor’s appointment scheduled for this afternoon can lead to better personal healthcare management. Many of these “technical helpers” merely require a microcontroller to process information based on the function(s) for which they are designed. By design, these technical helpers can be interconnected to provide a platform solution that can assist elderly living, with the end result being a person’s self-determined path to stay independent far longer.

Tomorrow’s need is already on us today, yet 8-bit microcontrollers will play a far larger role than many now imagine. The actions we take today will be the ones we ourselves will live with tomorrow, through creative solutions that leverage smart MCUs. As a result, we will protect not only our aging loved ones who can then enjoy a better quality of life, but we will also creatively leverage those wonderful microcontrollers so that we, like our parents, can live more independently in the future.

What is the right technology solution for a huge global need? Statistically speaking, our world faces a looming crisis that – while it doesn’t hit the headlines often – will eventually affect every single person on our planet, and affect us in crucial ways. The crisis? Our aging population – and an avalanche of need that could likely fall 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 possesses more than twenty years of technical engineering and marketing management experience, leading branding and marketing programs. Prior to coming onboard with Zilog, Steve held marketing management and technical engineering roles at Intel Corporations for over 14 years where he had several teams driving new technologies directly relating to the current products initiatives. His teams drove worldwide programs in evangelizing new technologies and accelerate adoption. Steve has a Marketing Degree from the University of Oklahoma. ■


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