Benedetto VignaExecutive VP & GM of Analog, MEMS and Sensors Group of STMicroelectronics

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4Benedetto VignaExecutive VP & GM of Analog MEMS and

Sensor Groups at STMicroelectronicsHow one of the largest semiconductor

companies is revolutionizing the MEMS and sensor areas.

10Featured ProductsThis week’s latest products from EEWeb.

14Shaping the Future of MEMS & Sensors

How MEMS microphones deliver breakthrough innovation in sound sensing.

22The AXP Logic Family

NXP’s new logic family addresses the industry trends of faster performance and lower power

consumption.

28Measuring Low Current Applications

How picoammeters offer the economy and ease of use of a digital multimeter with

significantly better low current sensitivity.

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STMICROELECTRONICS is one of the world’s largest semiconductor companies headquartered in Geneva, Switzerland. The company is known to have one of the broadest product portfolios, especially in the MEMS and sensor markets. Their diverse microelectronics products can be found in everything from mobile phones to popular gaming consoles.

The company’s Executive Vice President and General Manager of the MEMS and Sensors Group, Benedetto Vigna, joined the company’s MEMS division back in 1995. Since then, he has steered the company to develop an ever-expanding MEMS product portfolio that has resulted into mass adoption in many consumer products. We spoke with Vigna about the next big wave of MEMS, what types of sensors have been growing in demand, and the ways in which the company is constantly innovating.

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INTERVIEW

STMICROELECTRONICS is one of the world’s largest semiconductor companies headquartered in Geneva, Switzerland. The company is known to have one of the broadest product portfolios, especially in the MEMS and sensor markets. Their diverse microelectronics products can be found in everything from mobile phones to popular gaming consoles.

The company’s Executive Vice President and General Manager of the MEMS and Sensors Group, Benedetto Vigna, joined the company’s MEMS division back in 1995. Since then, he has steered the company to develop an ever-expanding MEMS product portfolio that has resulted into mass adoption in many consumer products. We spoke with Vigna about the next big wave of MEMS, what types of sensors have been growing in demand, and the ways in which the company is constantly innovating.

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What sensor product lines does ST have?

ST is a company with a rainbow of MEMS products. We have seven different kinds of MEMS—one for each color of the rainbow. We have temperature sensors, gyroscopes, magnetic sensors/compasses, microphones, pressure sensors, inkject/microfluidics and multisensor packages. We are also investing heavily in other types of sensors such as environmental MEMS like humidity sensors and other non-MEMS sensors such as Touch Sensors, where we have our FingerTip technology. We are developing Smart Sensors that embed the Microcontroller and we want to make all of these sensors available in wireless options, because in some cases the wires are inconvenient or impractical. I would define the position of ST as a broad range supplier of sensors and we are constantly looking to expand our portfolio.

Are you looking at module solutions to be integrated into your wireless sensors?

We offer our customers the choice to integrate both the sensing features and the wireless communication features in the same package. I believe the next big wave of MEMS is going to be wearable technologies and you are going to see sensors distributed in the environment around us. When you wear technology that interacts with distributed sensors, what does it need? It needs the wireless sensor, which needs a battery. If you want to put sensors in your shoes, for example, you don’t want to walk around with a wire that runs down your leg to your shoe to capture the sensor data. Better to put a wireless radio with the sensor to transmit the data.

In terms of a product like this, do you feel that ST is going to provide all of the technologies needed within that one package, or will you be partnering with other people?

We will provide the customer with one package because that is what they want. Today, we have all the components—the sensor and we also have Bluetooth and low-energy Bluetooth for more consumer-oriented applications. We have a radio as well that will address the smart environment applications. For example, we are working with a company to put a wireless radio in streetlights in a couple of cities all over the world—we mentioned a few weeks ago that the lights are rolling out in Paris, the City of Lights. When you put a wireless radio into a streetlight, you can add sensors into the mix and communicate among the streetlights to save power when no one is on the street or adjust the lights as the sun rises or sets. That’s the rationale behind the next big wave—wearable technologies and the smart environment.

What type of radio do you have in these packages?

We have two radios. One is Bluetooth and the other one is called the SPIRIT1, which is a low-power, low-frequency radio that works below one gigahertz. It is a radio that has the longest range—up to several kilometers, depending on the environment--and it’s more robust than Bluetooth. If it’s raining or there is a thick wall, there will be no interference with the SPIRIT1 radio. Also, you would not use Bluetooth for an application where security was important. Instead, you can use this SPIRIT1 radio to add communication to more sensor applications like with metering and automation, where you need to protect data.

“ You will soon see products from ST that allow us to continue to shrink the technology while still maintaining high performance.”

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INTERVIEWIn recent years, what kinds of sensors have been growing the most?

Most recently, the product that has been growing the fastest has been the gyroscope. Today, a lot of people are integrating the gyroscope together with an accelerometer. In absolute numbers, these are the things that have been growing most. Along with gyroscopes, the use of pressure sensors and microphones has also been growing very rapidly.

What gyroscope options does ST provide?

We have gyroscopes that cover the full range of applications that the industry is asking for. We have a gyroscope that is much more full-scale from degrees per second up to 6,000 degrees per second. When you take pictures, and you need adjustment sfor optical stabilization, you need a more full-scale option because the small movements of the hand produce more vibration. When you play with a mobile phone or game console, the movement of your hand is faster around 2,000 degrees per second. ST has a complete portfolio of gyroscopes for all applications that our customers are designing.

We have single-axis, dual-axis, and triple-axis gyroscopes, which are the most complex ones we offer. ST is the market leader for three-axis gyroscopes in the consumer market, and we are also the only manufacturer that has the three-axis gyroscope fully qualified for the automotive industry—and available in million-piece quantities. In addition, ST is the only manufacturer whose gyros can cope with ultrasonic cleaning and the drop test; it is exceptionally rare to be able to combine good performance with strong mechanical resistance.

Is there a lot of innovation stilltaking place with MEMS processes and capabilities?

Beyond the progress we’re making in processing, there is definitely development in the software and technology. You will soon see products from ST that allow us to continue to shrink the technology while still maintaining high performance. Just recently, we announced the development of a new technology for pressure sensors—the first

technology that allows you to use a fully molded package incorporating an isolated sensing element for pressure sensors to make the sensor more accurate and more robust.

Smartphones and tablets have been the launching pad for gyroscopes and microphones and we believe these applications will boost pressure sensors, too. Like other components, the sensors must be small. We announced that we were able to miniaturize the pressure sensor down to 2 by 2 millimeters. Think of the pressure sensor as an empty room in a house. We found a way to fill a room of the house with plastic in a way that is more robust while we leave a hole for the air pressure to get through only when it’s needed.

Today, I believe that sensor technology is just as important as software development in the development of new applications. You can simplify the software, but when you announce an improvement to the sensor, it enables the development of better applications for the customer.

The motions of ST’s gyroscopes

“ST is the only manufacturer whose gyros

can cope with ultrasonic cleaning and the drop test;

it is exceptionally rare to be able to combine good

performance with strong mechanical resistance.”

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In a mobile phone, pressure sensors can help determine if you are going up stairs or down. The weight of the atmosphere increases and decreases depending on altitude. In Death Valley, the weight of the atmosphere is much heavier than in the Rocky Mountains because there is less oxygen and air at higher elevations. We have a very sensitive device that can sense the pressure variations when you go step by step up the stairs. ST pressure sensors can even detect the pressure difference of 10 centimeters. What could you do with this? This resolution would be very valuable for indoor navigation. Combining a pressure sensor with a gyroscope, accelerometer, and e-Compass can completely replace GPS when you are indoors and there is no signal.

What is the e-Compass?

The compass is another product that is going to be used more and more in mobile devices. In addition to the pressure sensor, we recently announced a new accelerometer and compass in a 2x2mm package—the smallest available for a 6-axis compass. This is very important because the accelerometer tells you how many steps you take, but the compass tells you in which direction you took those steps. The compass is meant for navigation, but that isn’t its only use. It is also ideal for the user interface for gaming. Still, I believe the compass will help enable a broad range of applications using indoor navigation.

Could you talk a little more about ST’s upcoming conference?

The Shaping the Future of MEMS and Sensors confer-ence has two main benefits. First of all, it serves as an opportunity for us and speakers from across the country to talk about the latest news and to share with the audience our vision for the future. Also, because we’ve tried to make it as interactive as possible, it will offer our customers and partners an opportunity to share their views on the future in terms of using sensors in their products. We’ve invited the Who’s Who of the industry to come and talk about how they are using MEMS and Sensors to Shape the Future and they will help us showcase how Sensors will improve how we work, live, and play. ■

“ Today, I believe that sensor technology is just as important as software development in the development of new applications.”

Sensors Will Become UbiquitousFrom location-based services to wearable sensors for health and wellness; from gaming and remote controls to sensors for safety and performance; from your smartphone to your tablet; expect to find a sensor--in fact, many sensors--in most all designs of the future, improving the way we work, live and play. You are invited to participate in a FREE full day Shaping the Future of MEMS and Sensors Summit, on September 10, 2013 at the Santa Clara Marriott Hotel, CA, that will feature thought-provoking keynotes and panel discussions, stimulating pres-entations, live demonstrations and hands-on seminars. The goal? To identify, highlight and help you take advantage of important trends in technology. Top technologists from industry and research organizations will demonstrate how they are adopting sensors to enable applications, augment the user experi-ence, and expand markets. Industry visionaries will describe where the next-generation of sensors is creating opportunities to shape the future of electronics.

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High-Speed CAN TransceiverThe TJA1043 belongs to the third generation of high-speed CAN transceivers from NXP Semiconductors, offering significant improvements over first- and second-gener-ation devices such as the TJA1041A. It offers improved ElectroMagnetic Compatibility (EMC) and ElectroMagnetic Discharge (ESD) performance, very low power con-sumption, and passive behavior when the supply voltage is turned off. These features make the TJA1043 the ideal choice for high speed CAN networks containing nodes that need to be available all times, even when the internal VIO and VCC supplies are switched off...Read More

Low-Loss, Ultra-Miniature Power MOSFETRenesas Electronics Corporation announced the availability of eight new low-loss P- and N-channel power metal-oxide-semiconductor field-effect-transistor (MOSFET) products optimized for use in portable electronics including smartphones and tab-lets. Featuring industry-leading low loss (low on-resistance), the new devices include the 20 V (VDSS) µPA2600 and the 30 V µPA2601, equipped in ultra compact 2 mm × 2 mm packages to deliver increased power efficiency and miniaturization within smaller mobile device form factors...Read More

Surface Mount Auto Focus LampThis High Brightness Orange LED Light Source is a high performance device, Avago Technologies ASMT-FJ10-ADH00 is a SMT (Surface Mount Technology) dome lamp uses an untinted, nondiffused lens to provide a high luminous intensity within a narrow radiation pattern. The device is made by encapsulating LED chip on axial lead frame to form molded epoxy lamp package with 6 bended leads for surfacing mounting. The LEDs have lenses, which focus the beam at about 10mm from the front of the lens, from where the beam diverges relatively slowly...Read More

32-Mbit High-Temp Flash MemorySM28VLT32 is a 32-Megabit Flash Memory designed to store program code and/or data from acquisition. The wide temperature rating of this device makes it ideal for applications that need to perform reliably in harsh environments. SM28VLT32 with its serial peripheral interface (SPI) offers low pin count for additional reliability and easy assembly in these applications. The memory is partitioned as sectors to provide ad-dressing of 2-M words of 16 bits each...Read More

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FEATURED PRODUCTS

Ultra Low-Noise Voltage ReferenceIntersil Corporation introduced the industry’s most precise and lowest output noise radiation hardened voltage references. Available in space saving surface mount packaging, ISL71090SEH12 and ISL71090SEH25 extend Intersil’s market-leading cat-alog of devices for the latest generation of telemetry equipment, data acquisition systems and high-end instrumentation products in space and satellite applications. System designers for modern space applications have had to make performance tradeoffs to meet stringent radiation hardened requirements...Read More

2D/3D HMI Software Development PlatformCGI Studio is a software development platform for the creation of 2D and 3D graphical interfaces (HMI/GUI) for automotive instrument clusters and infotain-ment systems. Part of the application suite, CGI Studio offers automotive system designers a powerful Microsoft Windows® based solution to shorten develop-ment time for advanced automotive applications. The application allows plat-form-independent abstraction and fully supports the OpenGL 2.0 ES standard to give system designers the greatest possible design flexibility...Read More

DC-DC Power SupplyThe source-driver power supplies consist of a boost converter and an inverting buck-boost converter that generates +15V (up to +17V) and -15V (up to -17V), respectively. Both source-driver power sup-plies can deliver up to 200mA. The positive source-driver supply regulation voltage (VPOS) can be set either by using an I²C interface or by connecting an external resistor-divider. The negative source-driver supply voltage (VNEG) is always tightly regulated to -VPOS within ±50mV.

Features

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• VPOS + VNEG = ±50mV Tracking Accuracy• Measures Internal and Remote Diode Temperature Sensors• True Shutdown on All Outputs

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PMIC for Intel Atom ApplicationsThe IDTP9145 is a scalable, programmable, multi-channel PMIC specifically designed to support the power management requirements of Intel Atom processor-based SoCs. Unlike traditional solutions that require a different PMIC for different power requirements, the highly-versatile IDTP9145 leverag-es IDT’s intelligent, scalable, distributed power sources (IDTP9147), enabling system designers to add phases and output current to the internal DC/DC regulator as needed by the application. This feature minimizes development risk and offers tremendous flexibility for point-of-load regulation, circuit board routing, and thermal distribution...Read More

Temperature Sensor IC with 1.8V SMBusMicrochip Technology Inc. announced a new six-member family of tempera-ture sensor ICs called the EMC118X. This is the world’s first family of temp sen-sors with 1.8V SMBus and I2C communications which is required for interfacing to the latest generation of smartphone, tablet and PC chipsets. Additionally, this integrated low-voltage I/O support reduces cost and board space be-cause it is accomplished without an external voltage level shifter. These are also the first temp sensors to use an advanced sample frequency-hopping filter which enables temperature-monitoring traces of up to 8 inches in noisy environments with accurate readings...Read More

Highly Integrated Temperature SensorsMouser Electronics, Inc. is now offering highly integrated Temperature Sens-ing Solutions from Texas Instruments that will help speed the design cycle for the next generation of temperature sensors. These TI Temperature Sensing Solutions feature high-performance analog-to-digital converters (ADCs) and analog front end devices (AFEs). TI’s ADS1247 and ADS1248 high-integrated, 24-bit ADCs provide a complete front-end solution for temperature sensor applications, including thermal couples, thermistors, and resistance tempera-ture detectors (RTDs)...Read More

LoRho Battery Strap Series PTCThe new Littelfuse SL LoRho Battery Strap Series PPTC (polymer positive temper-ature coefficient) is designed with a proprietary conductive polymer material, to provide both over-current and over-temperature protection for rechargea-ble battery cells. This series features a slim, low profile and low resistance design to install directly on the latest generations of battery cells for a longer battery run time...Read More

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Dynamic Self-Calibrating Tooth Sensor ICThe ATS616 gear-tooth sensor IC is a peak-detecting device that uses automatic gain control and an integrated capacitor to provide extremely accurate gear edge detection down to low operating speeds. Each package consists of a high-temperature plastic shell that holds together a samarium-cobalt pellet, a pole piece, and a differential open-collector Hall IC that has been optimized to the magnetic circuit. This small package can be easily assembled and used in con-junction with a wide variety of gear shapes and sizes...Read More

Low Power Capacitive Touch SensorThe AK4160 is a low operating voltage and low power consumption 16-channel capacitive touch sensor. It has a maximum of 8 channels out of the 16-channel that can be configured to LED drive or GPIO. The AK4160 has a channel independ-ent automatic correct function of environmental drifts for each sense input. It reduces false detection by continuous calibration of the internal reference value in the situation when the input capacitance of the touch switch is changed by external factors such as hydrothermal conditions. The automatic initial setting func-tion sets the charge current and charge time according to the size and the shape of a touch switch...Read More

Automotive SPI Bus 2Kbit EEPROMBR25H020-2C is a serial EEPROM of SPI BUS interface method. Features:• High speed clock action up to 10MHz (Max.)• Wait function by HOLDB terminal.• Part or whole of memory arrays settable as read only memory area by program.• 2.5V to 5.5V single power source action most suitable for battery use.• Page write mode useful for initial value write at factory shipment.

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MOST-Compliant Optical TransceiverThe MLX75605 device is a Fiber Optics Transceiver (FOT), dedicated for optical MOST150 (Media Oriented System Transport) protocol network (over 1 mm PMMA Plastic Optical Fiber). The optical transmitter consists of a 650nm LED with driver circuitry. It also has integrated memory cells allowing parameter trimming. Thanks to this strategy it is possible to compensate for any variation in the production process and guaran-tee extremely stable specifications. Moreover this trim and test pro-cedure is also performed at extreme temperatures such that an inte-grated temperature sensor allows temperature dependent parameter trimming (e.g. increased drive current to compensate for reduced LED output power at high temperatures)...Read More

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Deliver a Breakthrough Innovation in Sound Sensing

INTRODUCTION TO MEMS MICROPHONES

A MEMS microphone is a solid state integrated IC that can sense voice in the same way as an ECM Microphone [Electret Condenser Micro-phone]. MEMS microphones are widely adopted in modern devices such as mobile phones, tablets, laptops, smart TVs, automotive voice recognition products, gaming and remote controllers.

Vishal Goyal – Technical Marketing Manager, STMicroelectronics India

EMSMicrophones

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TECH ARTICLE

Deliver a Breakthrough Innovation in Sound Sensing

INTRODUCTION TO MEMS MICROPHONES

A MEMS microphone is a solid state integrated IC that can sense voice in the same way as an ECM Microphone [Electret Condenser Micro-phone]. MEMS microphones are widely adopted in modern devices such as mobile phones, tablets, laptops, smart TVs, automotive voice recognition products, gaming and remote controllers.

Vishal Goyal – Technical Marketing Manager, STMicroelectronics India

EMSMicrophones

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According to IHS iSuppli, the market for MEMS microphones for consumer electronics and mobile handsets

is forecast to grow revenue at a CAGR of 23% between 2010 and 2014. By 2015, the shipments of MEMS microphones are expected to reach 2.9 billion units - four times the total in 2010. The increased popularity of MEMS microphones is attributed to their reliable monolithic structure, high tolerance of mechanical vibration, small footprint and height, and optional digital output.

In addition, MEMS microphones enable dramatic advancements in sound quality in multiple-microphone applications. Such microphone arrays, facilitated by the small form factor, superior sensitivity matching and frequency response, enable the implementation of active noise and echo cancelling, as well as beam-forming, a sound-processing technology that helps isolate a sound and its location. These features are invaluable with the increasing use of cell phones and other devices in noisy and uncontrollable environments.

MEMS Microphone Construction

There are mainly two types of MEMS microphones – Analog, which convert sound into corresponding voltage output, and Digital, which gives a digital output, typically pulse density modulation [PDM].

Acoustic Transducer

A MEMS microphone is also serves as an acoustic transducer. The transduction principle is the coupled capacity change between a fixed plate (back-plate) and a movable plate (membrane). This capacitive change is caused by the sound wave passing through the acoustic holes. This moves the membrane modulating the air gap comprised between the two conductive plates. The back-chamber of the MEMS microphone is the acoustic resonator. The ventilation hole allows the air compressed in the back chamber to flow out and consequently allowing the membrane to move back.

Key Parameters of MEMS Microphones

Sensitivity

The sensitivity is the electrical signal at the microphone output to a given acoustic pressure as input. The reference of acoustic pressure is 1Pa or even 94dBSPL @ 1kHz**. The sensitivity of a MEMS microphone is typically measured as follows:

- Analog microphones in mV/Pa or even dBV = 20 * Log (mV/Pa / 1V/Pa).

- Digital microphones in %FS or even dBFS = 20 * Log (%FS / 1FS).

MEMS Microphones

“ MEMS microphones enable dramatic advancements in sound quality in multiple-microphone applications.”

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Directionality

The directionality indicates the variation of the sensitivity response with respect to direction of arrival of the sound. Some MEMS microphones are OMNI-Directional, which means there is no sensitivity change at any sound source position in the space. The directionality can be indicated in a Cartesian axis as sensitivity drift vs. angle or in a polar diagram showing the sensitivity pattern response in the space.

Signal to Noise Ratio [SNR]

The signal-to-noise ratio specifies the ratio between a given reference signal to the amount of residual noise at the microphone output. The reference signal is the standard signal at the microphone output when the sound pressure is 1Pa @ 1kHz. In other words, this is the microphone sensitivity.

The noise signal (residual noise) is the microphone electrical output at the silence. This quantity includes both the noise of the MEMS element and the ASIC. Typically the noise level is measured in an anechoic environment and weighting-A the acquisition. The A-weighted filter corresponds to the human ear frequency response.

Dynamic Range and AOP

The dynamic range is the difference between the minimum and maximum detectable sound by the microphone without distortion. The maximum signal that the microphone can “listen” without distortion is also called acoustic overload point (AOP). The minimum signal that a microphone can “hear” depends on its SNR. In other words, the minimum signal is equivalent to the residual noise in terms of dBSPL.

Frequency Response

The frequency response of a microphone in terms of magnitude indicates the sensitivity variation across the audio band. This parameter also describes the deviation of the output signal from the reference 0dB. Typically, the reference for this measurement is the exact sensitivity of the microphone → 0dB = 94dBSPL @ 1kHz. The typical frequency response of a microphone shows a roll-off at low frequency due to the ventilation hole and a rise up at high frequency due to the Helmholtz effect.

The frequency response of a microphone in terms of phase indicates the phase distortion introduced by the microphone. In other words, it indicates the delay between the sound wave moving the microphone membrane and the electrical signal at the microphone output. This parameter includes both the distortion due to the membrane and the ASIC

The signals of a couple of microphones are processed** to shape the response along the x direction

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Directional Acoustic Patterns Using MEMS Microphones

An omnidirectional microphone response is generally considered to be a perfect sphere in three dimensions. The smallest diameter microphone gives the best Omni-directional characteristics at high frequencies. But MEMS microphones can also be used in array to modify the response according to desired acoustic patterns

The challenging requirements of distant-speech interaction systems require specific physical and acoustic parameters from MEMS microphones. A small form factor allows designers to easily embed entire arrays of microphones in the walls, desks, or speech-enabled appliances of the automated home, while the microphones’ excellent acoustic characteristics, coupled with sophisticated signal-processing technologies, would make it possible to identify and capture an individual speaker from several meters away, in a crowded room with music playing.

The distant-speech interaction capability of MEMS microphones will not only dramatically change the way people interact with technology, but can make a real difference for those who can’t easily move around, such as those who are motor-impaired. In addition to home-based scenarios, distant-speech interaction systems can find use in robotics, tele-presense, surveillance and industry automation.

Multiple microphones in array are becoming standard in mobile devices, supporting advanced features such as voice command, noise suppression and high-definition video recording.

Packaging

While there are some MEMS microphone manufacturers that still produce devices with metallic lids, plastic packages can save space and increase durability in consumer and professional voice-input applications, from mobile phones and tablets to noise-level meters and noise-cancelling headphones.

To further simplify design in space-constrained consumer devices, MEMS microphones that are suitable for assembly on flat-cable printed-circuit boards streamline manufacturing.

While extremely difficult to do, providing a package technology that allows equipment manufacturers to place the ‘sound hole’ either on the top or the bottom of the package delivers the greatest flexibility to ensure the slimmest possible design and shortest acoustic path from the environment to the microphone. While the microphones with the sound hole on the top (top-port) suit the size and sound-inlet position requirements of laptops and tablets, the bottom-port microphones are mostly used in mobile phones.

Conclusion

MEMS microphone are entering new application areas such as voice-enabled gaming, automotive voice systems, acoustic sensors for industry and security applications, and medical telemetry. Its unique construction, performance and form factor has made possible what was unthinkable earlier.

We hope you will consider joining us on September 10th at the Shaping the Future of MEMS and Sensors Summit at the Marriott Hotel in Santa Clara, CA. Shaping the Future of MEMS and Sensors is sponsored by Berkeley Sensor and Actuator Center (BSAC), EEWeb, EEJournal, MEMS Exchange, MEMS Industry Group, MEPTEC, and Mouser Electronics and hosted by STMicroelectronics. ■

http://bit.ly/SJ9ugm

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NXP is a leader in low power capacitance touch sensors, which work based on the fact that the human body can serve as one of the capacitive plates in parallel to the second plate, connected to the input of the NXP capacitive sensor device.

Thanks to a patented auto-calibration technology, the capacitive sensors can detect changes in capacitance and continually adjust to the environment. Things such as dirt, humidity, freezing temperatures, or damage to the electrode do not affect the device function. The rise of touch sensors in modern electronics has become a worldwide phenomenon, and with NXP’s low power capacitive sensors it’s never been easier to create the future.

Learn more at: touch.interfacechips.com

World’s lowest power capacitivesensors with auto-calibration

eeweb.com/register

Join TodayNXP is a leader in low power capacitance touch sensors, which work based on the fact that the human body can serve as one of the capacitive plates in parallel to the second plate, connected to the input of the NXP capacitive sensor device.

Thanks to a patented auto-calibration technology, the capacitive sensors can detect changes in capacitance and continually adjust to the environment. Things such as dirt, humidity, freezing temperatures, or damage to the electrode do not affect the device function. The rise of touch sensors in modern electronics has become a worldwide phenomenon, and with NXP’s low power capacitive sensors it’s never been easier to create the future.

Learn more at: touch.interfacechips.com

World’s lowest power capacitivesensors with auto-calibration

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Introduces AXP Logic Family to Address the Need for Lower Power Consumption

We talked with NXP’s International Product

Manager, Cliff Lloyd, about the new AXP Logic family released in July, and how it takes

on the power-consumption problem.

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FEATURED ARTICLE

Introduces AXP Logic Family to Address the Need for Lower Power Consumption

We talked with NXP’s International Product

Manager, Cliff Lloyd, about the new AXP Logic family released in July, and how it takes

on the power-consumption problem.

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“The mobility markets have been exploding in recent years,” NXP’s International Product Manager, Cliff Lloyd told us. “That market is driven by two primary factors: one is the size of a device, and the other is battery life.” In the past, he explained, NXP focused on making smaller and smaller packages. NXP made a breakthrough last year in small package size when it released its Diamond package -- 0.8 by 0.8 in size with a 0.5mm pad pitch between pads -- which made it easier to mount in PCBs. After the Diamond package was released and package size addressed, NXP decided to focus on addressing low power consumption in the mobility market. “We felt we had to address the need for faster performance... and also maintain or improve power savings performance,” said Lloyd.

]There are two very important parts to power savings performance, explained Lloyd. The first is static power consumption, which is the amount of power a device uses when it is simply connected to a battery. The other important part of power consumption is the power that’s consumed when the device is actually being used, which is called the Dynamic Power Consumption.

Keeping these two parts of power consumption low was what NXP has aimed to address with the AXP family. What they have achieved with the AXP family is 15% lower power consumption for unique functions, as well as a top delay of 4 nanoseconds at 1.2V, which is about twice as fast as its previous AUP family at the same voltage node.

One of the advantages of the AXP family of devices is its configurable logic, which gives customers a lot of flexibility when selecting parts. For instance, when a customer buys a device -- depending on how he hardwires it on the PCB -- the device could operate as a NAND Gate, an OR Gate, a NOR Gate, a buffer, or an inverter, and the customer doesn’t have to buy a different device to program these individual functions. The customer can get different functions from one device, and use a single qualification to cover multiple functions, which offers tremendous flexibility.

[“We felt we had to address the need for faster performance... and also maintain or improve power savings performance.”

- Cliff Lloyd, NXP

One of the advantages of the AXP family of devices is its configurable logic, which gives customers a lot of flexibility when selecting parts.

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FEATURED ARTICLE

Although many people believe that the devices are programmable, Lloyd explained that that is a misconception. The devices are strictly hardwire configurable on the PCB. For example, if you hooked up pin 5 and pin 3, as in the figure below, you would get a two-input AND gate. If you connected pin 2 and pin 1 to ground, you would get a two-input NOR gate. It all depends on how the board is laid out -- an inverter, or an exclusive NOR (XNOR) can also be achieved. Because of this flexibility, NXP decided to first release the configurable devices.

Features of AXP Devices

• Very low dynamic power dissipation (CPD) • tpd of 2.9 ns at Vcc of 1.8 V • Wide supply voltage range (0.7 V to 2.75 V) • Fully specified at 0.8 V • Schmitt-trigger action on all inputs • 4.5 mA balanced output drive • Over-voltage tolerant I/Os • Fully specified (-40 to +85 °C) • Pb-free, RoHS compliant and Dark Green

For more information, visit the NXP Tech Community.

With low static and dynamic power dissipation, a wide voltage range, true Schmitt-Trigger inputs, and configurable logic, NXP has aimed to address the need for low power consumption and reliable logic level switching with the AXP Logic family, and position itself for a mobile market where battery critical applications and battery life conservation is key.

Power Factor Correction ControllersISL6730A, ISL6730B, ISL6730C, ISL6730DThe ISL6730A, ISL6730B, ISL6730C, ISL6730D are active power factor correction (PFC) controller ICs that use a boost topology. (ISL6730B, ISL6730C, ISL6730D are Coming Soon.) The controllers are suitable for AC/DC power systems, up to 2kW and over the universal line input.

The ISL6730A, ISL6730B, ISL6730C, ISL6730D are operated in continuous current mode. Accurate input current shaping is achieved with a current error amplifier. A patent pending breakthrough negative capacitance technology minimizes zero crossing distortion and reduces the magnetic components size. The small external components result in a low cost design without sacrificing performance.

The internally clamped 12.5V gate driver delivers 1.5A peak current to the external power MOSFET. The ISL6730A, ISL6730B, ISL6730C, ISL6730D provide a highly reliable system that is fully protected. Protection features include cycle-by-cycle overcurrent, over power limit, over-temperature, input brownout, output overvoltage and undervoltage protection.

The ISL6730A, ISL6730B provide excellent power efficiency and transitions into a power saving skip mode during light load conditions, thus improving efficiency automatically. The ISL6730A, ISL6730B, ISL6730C, ISL6730D can be shut down by pulling the FB pin below 0.5V or grounding the BO pin. The ISL6730C, ISL6730D have no skip mode.

Two switching frequency options are provided. The ISL6730B, ISL6730D switch at 62kHz, and the ISL6730A, ISL6730C switch at 124kHz.

Features• Reduce component size requirements

- Enables smaller, thinner AC/DC adapters- Choke and cap size can be reduced by 66%- Lower cost of materials

• Excellent power factor over line and load regulation- Internal current compensation- CCM Mode with Patent pending IP for smaller EMI filter

• Better light load efficiency- Automatic pulse skipping- Programmable or automatic shutdown

• High reliable design- Cycle-by-cycle current limit- Input average power limit- OVP and OTP protection- Input brownout protection

• Small 10 Ld MSOP package

Applications• Desktop computer AC/DC adaptor

• Laptop computer AC/DC adaptor

• TV AC/DC power supply

• AC/DC brick converters

FIGURE 1. TYPICAL APPLICATION FIGURE 2. PFC EFFICIENCY

+

ISL6730

VCCISEN

ICOMP

VIN

GATEGND

FB

BO VREG

COMP

VLINE VOUT

VI

OUTPUT POWER (W)

EFFI

CIE

NC

Y (%

)

ISL6730C

ISL6730A, SKIP

100

95

60

65

70

90

85

80

75

0 20 40 60 80 100

TABLE 1. KEY DIFFERENCES IN FAMILY OF ISL6730

VERSION ISL6730A ISL6730B ISL6730C ISL6730D

Switching Frequency 124kHz 62kHz 124kHz 62kHz

Skip Mode Yes-Fixed Yes-Fixed No No

February 26, 2013FN8258.0

Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2013All Rights Reserved. All other trademarks mentioned are the property of their respective owners.

Get the Datasheet and Order Samples

http://www.intersil.com

Copyright 2013, Silicon Frameworks, LLC PCBWeb.com

ep page master fp.indd 1 3/11/13 10:34:41 AM

PULSE

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Jonathan TuckerSenior Marketer andProduct ManagerKeithley Instruments

Taking the Measure of

TECH ARTICLE

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Jonathan TuckerSenior Marketer andProduct ManagerKeithley Instruments

Taking the Measure of

When measuring electrical current, the goal is to insert an ammeter in series with

the circuit so that the current measured by the ammeter is identical to the current flow-ing through the circuit. In an ideal world, the meter would have absolutely no effect on the circuit; however, in real-world measurements, several error sources may contribute to sub-stantial uncertainty in the measurement result.

Digital multimeters (DMMs) are considered sufficiently accurate for most current measure-ments, but low level DC current measurements often demand greater sensitivity than these instruments can deliver. Generally, they lack the sensitivity required to measure currents less than 100nA. Even at higher current levels, a DMM’s input voltage drop (voltage burden) of hundreds of millivolts can make accurate current measurements impossible. Picoam-meters, in contrast, offer the economy and ease of use of a DMM with significantly better low current sensitivity. What makes these two types of instruments so different?

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Shunt Ammeter

Shunting the input of a voltmeter with a resistor forms a shunt ammeter (Figure 1a). The input current (IIN) develops an input voltage (EIN) across the shunt resistance (RSHUNT).

Note that the voltage sensitivity of the circuit is controlled both by the value of RSHUNT and the relative values of RA and RB.

Although using a larger value for RSHUNT might initially appear advantageous, RSHUNT should be made as small as possible for several reasons. First, low value resistors have greater time and temperature stability and a better voltage coefficient than high value resistors. Second, low resistor values reduce the input time constant and result in faster instrument response times. Finally, for circuit loading considerations, the input resistance RSHUNT of an ammeter should be small to reduce the voltage burden EIN. As a result, the RSHUNT value can have an impact on measurement performance.

Feedback Ammeter

Figure 1b shows the general configuration of a feedback-type ammeter. In this configuration, the input current (IIN) flows into the input terminal of the amplifier (A) and through the feedback resistor (RF). The low offset current of the amplifier changes the current (IIN) by a negligible amount.

Thus, the output voltage is a measure of the input current, and sensitivity is determined by the feedback resistor (RF). The low voltage burden (EIN) and corresponding fast rise time are achieved by the high gain operational amplifier, which forces EIN to be nearly zero.

Circuit analysis of Figure 1b shows that:

EOUT + IINRF = EIN EOUT = –AEIN, and EIN = – EOUT / A

Thus, EOUT + IINRF = – EOUT / A

Given that A>>1, EOUT = –IINRF and |EIN| = EOUT / A <<EOUT

The amplifier gain can be changed as in the shunt ammeter circuit using a combination of resistors RA and RB that are inserted into the feedback loop, forming a multiplier. The gain of the circuit is determined by the feedback resistor and by the relative values of RA and RB and is given as follows:

EOUT = –IINRF/(RA + RB)/RB

and again, EIN = – EOUT / A

SHUNT AMMETERS VS. FEEDBACK AMMETERS

The shunt method and the feedback ammeter methods are the two basic techniques for making low current measurements. The shunt configuration is used primarily in DMMs; modern picoammeters and electrometers use the feedback ammeter configuration.

Figure 1a: Shunt Ammeter Figure 1b: Feedback Ammeter

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TECH ARTICLE

LIFTING THE VOLTAGE BURDEN

The level of voltage burden involved─the voltage that appears across the ammeter input terminals when measuring─represents another important difference between a DMM and a picoammeter. As Figure 1a illustrates, the DMM shunt ammeter method requires voltage (typically 200mV) to be developed across a shunt resistor in order to measure current. This voltage burden will reduce the actual current flowing in the circuit, reducing the accuracy of the measurement. In contrast, a picoammeter’s feedback ammeter method reduces this terminal voltage by several orders of magnitude due to the high gain amplifier with negative feedback for the input stage. As a result, the voltage burden is greatly reduced—on the order of 200μV or less. This low voltage burden reduces both

Figure 2: Keithley Model 6482 and two-channel ion beam comparison (below)

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PULSEmeasurement errors and the minimum shunt cable resistance that must be maintained to provide a given meter accuracy.

Although the use of a picoammeter can substantially minimize errors in low current measurements, additional errors can arise from extraneous currents flowing through various circuit elements.

GETTING SWEPT AWAY BY NOISE CURRENTS

Noise current generators represent unwanted currents generated at a particular point in a circuit. These currents may result from triboelectric, piezoelectric, and electrochemical effects or from resistive leakage or dielectric absorption.

Triboelectric currents are generated by charges created at the interface between a conductor and an insulator due to friction between them. Here, free electrons rub off the conductor and create a charge imbalance that causes a current flow. A typical example would be electrical currents generated by insulators and conductors rubbing together in a coaxial cable. When minimizing noise is a priority, many system builders employ special low noise coaxial and triaxial cables to combat the effects of triboelectric currents.

Piezoelectric currents are generated when mechanical stress is applied to certain crystalline materials are used for insulated terminals and interconnecting hardware. In some plastics, pockets of stored charge cause the material to behave in a manner similar to piezoelectric materials.

Noise currents also arise from electrochemical effects. Here, ionic imbalances can create weak batteries between two conductors on a circuit board. For example, commonly used epoxy printed circuit boards can generate currents of several nano-amps when not thoroughly cleaned of etching solution, flux, perspiration, or other material. To prevent these error currents, all interconnecting circuitry should be thoroughly cleaned using a cleaning solvent such as methanol, and then be allowed to dry completely before use.

Dielectric absorption can occur when a voltage applied across an insulator causes positive and negative charges within that insulator to polarize. When the voltage is removed, the separated charges generate a decaying current through external circuitry as they recombine. The effects of dielectric absorption can be minimized by avoiding the application of voltages more than a few volts to insulators that are used for sensitive current measurements. If it’s impractical to avoid doing so, it may take minutes or even hours for these currents to dissipate.

PICOAMMETER APPLICATIONS

Ion beam detector alignment applications make good use of a picoammeter’s low current sensitivity. Measurements of ratio and delta (difference) between two channels can significantly improve efficiency in beam alignment applications by performing these calculations within the instrument itself. The beam alignment procedure is important in many different fields, from high energy particle beam monitoring to ion beam monitoring and fiber optics. It involves measuring a signal from a detector and adjusting the position of the source to align it to the sensor so that it matches a calibrated source/detector pair. Ratio and delta measurements can provide immediate feedback about how far out of alignment these beams are, which helps the operator adjust the source more quickly. Keithley’s Model 6482 Dual-Channel Picoammeter (Figure 2) incorporates ratio and delta measurement capabilities as well as dual voltage biases, which allow the sensors to be powered without the need for additional equipment.

Two-channel picoammeters are also well suited for other powered applications:

• Ion Beam Monitoring – Focused ion beam systems can be used in applications involving nanometer-scale imaging, micromachining, and mapping. Monitoring the magnitude of the beam current carefully with an ion detector is critical. These sensors accept ions and put out a small current. Multiple ion beams and sensors are often operated concurrently and require powered sensors.

• Multiple Device Testing – Multi-channel devices increase throughput and reduce maintenance burden by increasing the number of channels in the same form factor.

• Multi-pin Device Testing – Multi-pin devices, such as dual diodes, ICs, and other components often need multi-channel, simultaneous current testing. Multiple channels allow one instrument to take measurements on multiple pins, offering new testing options and increasing throughput. ■

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