Recent Feature Articles

ADIsimPower Provides Robust, Customizable DC-to-DC Converter Designs - January 2010

Designers of dc-to-dc converters are faced with an overwhelming number of options for power management ICs. Finding the best combination of features, performance, integration level, and price can be difficult enough, and the actual design work can be daunting. ADIsimPower™ simplifies the IC selection process and provides the information required to build an optimized dc-to-dc converter.

Designing High-Performance Phase-Locked Loops with High-Voltage VCOs - December 2009

Phase-locked loops are used to provide the local oscillator in radio receivers and transmitters; for clock distribution and noise reduction, and as the clock source for high-sampling-rate ADCs. This article considers the basics of PLLs, examines the current state-of-the-art in PLL design, discusses pros and cons of typical architectures, and introduces some alternatives to high-voltage VCOs.

Synchronizing Device Clocks Using IEEE 1588 & Blackfin Embedded Processors - November 2009

IEEE 1588 defines a protocol to synchronize distributed clocks on a network. The preferred clock synchronization method for many applications, it is cost-effective, supports heterogeneous systems, and provides nanosecond-level synchronization. The ADSP-BF518 Blackfin^® processor includes dedicated hardware support for IEEE 1588. This article shows clock synchronization performance obtained using this solution.

Isolation in High-Voltage Battery Monitoring for Transportation Applications - October 2009

Battery stacks for transportation can provide hundreds of volts. These high voltages can prove lethal to human beings—and even lower voltages can damage electronic equipment—so safety is a key concern. Although these stacks are inherently dangerous, they must still communicate with the cell monitoring electronics. Galvanic isolation is thus required to make the communications method safe and reliable.

Phase Response in Active Filters, Part 2: Low-Pass and High-Pass Responses - September 2009

The transfer function of an active filter can be viewed as the cascaded response of the filter transfer function and an amplifier transfer function. This article examines the phase shift of the filter transfer function itself. While filters are designed primarily for their amplitude response, the phase response can be important in applications such as time delay simulation, cascaded filter stages, and especially process-control loops.

The Basics of Video Decoders in Supervision and Inspection - August 2009

Video cameras—which range from inexpensive, low-definition black-and-white closed-circuit television systems to state-of-the-art high-definition digital-video systems—are found in diverse applications including product inspection, traffic monitoring, and real-time face recognition. Dropping unneeded data and passing only the essential parts of the picture can simplify the video system—saving memory and computational cycles.

Detecting Human Falls with a 3-Axis Digital Accelerometer - July 2009

Elderly individuals can suffer accidental falls due to weakness or dizziness. The initial injury can be further aggravated if treatment is not obtained within a short time. MEMS-based fall detectors can sense changes in body position by tracking acceleration, determine when an individual is falling, and issue an alert for assistance. This article describes the use of an ADXL345 three-axis digital accelerometer as a fall detector.

Digital Isolator Simplifies USB Isolation in Medical and Industrial Applications - June 2009

Despite its low speed and point-to-point nature, RS-232 was tolerated in medical and industrial applications because it was universally available, well supported, and allowed easy implementation of the required isolation. The ADuM4160 digital isolator allows simple, inexpensive isolation of full- and low-speed USB peripherals—including the D+ and D– lines—increasing the usefulness of USB in medical and industrial applications.

“Rules of the Road” for High-Speed Differential ADC Drivers - May 2009

Most modern high-performance ADCs use differential inputs to reject common-mode noise and interference, increase dynamic range by a factor of two, and improve overall performance. ADC drivers—circuits often specifically designed to provide differential signals—perform many important functions including amplitude scaling, single-ended-to-differential conversion, buffering, common-mode offset adjustment, and filtering.

PLC Evaluation Board Simplifies Design of Industrial Process-Control Systems - April 2009

The applications for industrial process-control systems range from simple traffic control to complex electrical power grids, from environmental control systems to oil-refinery process control. The intelligence of these systems lies in their measurement and control units. The two most common computer-based systems to control machines and processes are programmable logic controllers and distributed control systems.

Analog Microcontroller Forms Heart of Low-Cost, High-Efficiency PA Monitor - March 2009

Saving energy is crucial for efficient wireless network operation. Power amplifiers (PA), the core of base stations and repeaters, can account for more than half of their total power consumption. Monitoring and controlling the PA can: improve efficiency and reduce operating costs; maximize output power and achieve the highest possible linearity; and allow the system operator to discover problems and improve reliability.

Using MEMS Accelerometers as Acoustic Pickups in Musical Instruments - February 2009

MEMS microphones have begun to dominate the broad consumer market, including cell phones, Bluetooth headsets, personal computers, and digital cameras. Now, key technologies used in MEMS accelerometers can bring a new dimension to acoustic transducers. Low-g accelerometers don't suffer from traditional feedback problems, and show clear potential as high-quality acoustic pickups for musical instruments.

Smart Metering Technology Promotes Energy Efficiency for a Greener World - January 2009

We’re all familiar with the electricity meter in the garage or basement. We may even have looked at it once or twice to phone an up-to-date reading to the utility company in place of an estimate. Thanks to technology, a quiet revolution is taking place inside this innocuous looking meter. This article describes how automatic meter reading and the smart grid can help improve energy efficiency and reduce carbon emissions.

Analog Front End for Femto Base Stations Brings Wireless Connectivity Home - December 2008

Imagine a device that can provide high-quality cellular reception within your home, allowing you and your family unlimited voice and data usage for a low monthly fee. A femto base station, usually referred to as a femtocell, provides all that and more. This small wireless device, which improves local wireless coverage when placed in a home or office, is poised to dramatically change the wireless infrastructure landscape.

Considering Multipliers, Part 1 [The Wit and Wisdom of Dr. Leif–7] - November 2008

Multipliers exploiting translinear loops, current-mirrors, current conveyors, and linear g_m cells continue to be indispensable more than sixty years since the very first fully monolithic ICs were fabricated in 1967. In this futuristic tale, Drs. Newton Leif and Niku Chen discuss multiplier topologies, uses, and history. Leif also provides some hints as to how neurons, which are translinear, behave exactly like bipolar junction transistors.

Design, Simulate, and Document Proprietary Wireless Systems - October 2008

The broad acceptance of standards developed for short range wireless connectivity has been one of the notable features of the semiconductor market in the past few years. These standards include Bluetooth, various flavors of Wi-Fi, ZigBee, and new emerging standards, such as Wibree/Bluetooth ULP and Ultra Wideband. The available wireless standards are not always the best fit for the application’s requirements, however.

Maintaining Public Railways with Lower Cost and Improved Safety - September 2008

A new, systematic maintenance approach now makes it possible to measure, locate, and fix rail- and tramway defects when they appear. Mature railway-engineering know-how and cutting edge technologies—including Blackfin processors and graphical system design techniques—combine to improve and optimize public transportation. This can result in longer operation lifetimes for rails, improving economy and reliability.

Impedance Measurement Monitors Blood Coagulation - August 2008

Blood coagulation is a complex process by which clots are formed to end bleeding at an injured site. During heart-bypass surgery, blood is diverted to a heart-lung machine. An anticoagulant is administered during surgery—followed by a rapid reversal. This article describes a coagulation monitor that provides rapid, automated data—aiding patient safety, workflow, and decision making—and leading to improved outcomes.

Fingerprint Sensor and Blackfin Processor Enhance Biometric Identification - July 2008

The need for effective, efficient security is manifest in today’s world. Individuals must be identified to allow or prohibit access to secure areas—or to enable them to use a computer. Biometric signatures identify individuals by measuring unique physical and behavioral characteristics using: a sensor, feature extraction, pattern matching, and decision making—allowing a user’s claimed identity to be authenticated or rejected.

Noise Figure and Logarithmic Amplifiers [The Wit and Wisdom of Dr. Leif—6] - June 2008

Log amps are uniquely equipped as RF measurement elements at frequencies from near-dc up to 12 GHz because of their wide dynamic range, temperature stability, excellent log conformance, and ease of use—with measurements provided directly in decibels. Noise figure is a valuable metric when log amps are used in the signal path, as it indicates the system's ability to extract information in the presence of noise.

Understanding Hot-Swap Controllers: Hot-Swap Circuit Design Example - May 2008

High-availability systems, such as servers, network switches, redundant-array-of-independent-disk (RAID) storage, and other forms of communications infrastructure must be designed for near-zero downtime throughout their useful life. Components that fail or need updating must be replaced without interrupting the rest of the system. This process, known as hot-swapping or hot-plugging, requires a hot-swap controller.

Discrete- and Integrated Control of Power Amplifiers in Base Stations - April 2008

In wireless base stations, the power amplifier dominates the performance in terms of power dissipation, linearity, efficiency, and cost. Monitoring and controlling the PA makes it possible to maximize the output power while achieving optimum linearity and efficiency. This article discusses the elements of a monitoring-and-control solution for the PA using discrete components—and describes an integrated solution.

Cooking Inductively: ADI iCoupler Technology Isolates Hob and User Interface - March 2008

Easy-to-use inductive cooking surfaces (hobs) are significantly safer, without flames or other direct heat sources on the hob. They have better overall performance, including faster heating time, and are gaining acceptance by consumers as they are becoming more affordable. Designing the circuitry that drives the inductive plate to heat metal pots requires an understanding of a wide variety of physical principles and techniques.

Analog/Digital-Converter Clock Optimization: A Test Engineering Perspective - February 2008

The entire system-clock signal chain must be understood in order to achieve optimal performance from an A/D converter. It can be discouraging to find that a circuit's accuracy is clock-jitter limited, as this problem could have been prevented during the design phase. Decreased clock jitter can be achieved through frequency division, filtering, use of an improved clock source, and proper choice of auxiliary hardware.

High Side Current Sensing: Difference Amplifier vs. Current-Sense Amplifier - January 2008

Accurate high-side current sensing is necessary in applications such as motor control, solenoid control, and power management. In these applications, monitoring the current on the high side permits improved diagnostic capabilities and maintains the integrity of the ground path by avoiding the introduction of shunt resistance. The sensing circuitry  must reject high common-mode voltages, while providing high gain and high accuracy.

Switching-Regulator Insights—Achieving Longer Battery Life in DSP Systems - December 2007

Step-down dc-to-dc switching regulators efficiently derive a low voltage from a higher voltage, maintaining a constant output despite variations in supply voltage or load current. This article describes an architecture that provides good regulation, high efficiency, and fast response, showing both fixed-voltage operation and a resistor-programmable circuit that provides dynamic voltage scaling in DSP applications.

Faster Open-Loop Gain Measurements (Ask The Applications Engineer—38) - November 2007

It is often desirable to measure the performance of a feedback network in a particular configuration so as to model the open-loop behavior. But this type of measurement is often challenging due to high gains, small input signals, and long settling times. This article shows you how to characterize the frequency response of the network rapidly and with minimal effort, using available tools and a small amount of special circuitry.

Phase Relations in Active Filters - October 2007

In applications that use filters, the amplitude response is generally of greater interest than the phase response. When a filter is used inside a process control loop, however, the total phase shift is of concern, since it may affect loop stability. This article looks at first- and second-order filters, comparing phase response as a function of topology, order, and Q. Higher-order filters are treated as cascades of lower-order blocks.

Toward More-Compact Digital Microphones - September 2007

As electret microphones become smaller, their element capacitance decreases. JFET preamps no longer suffice, as their relatively large input capacitance attenuates the signal from the microphone. Much can be gained by replacing JFET amplifiers with CMOS analog and digital circuitry, including easier gain setting, multiple functional modes, direct digital outputs, enhanced sound quality, and higher noise immunity.

Avoid Common Problems When Designing Amplifier Circuits - August 2007

Modern op amps and in-amps provide great benefits to the designer, and a great many clever, useful, and tempting circuit applications have been published. But all too often, in one’s haste to assemble a circuit, some very basic issues are overlooked, leading to the circuit not functioning as expected—or perhaps at all. This article will discuss a few of the most common application problems and suggest practical solutions.

The AD9271—A Revolutionary Solution for Portable Ultrasound - July 2007

Medical ultrasound systems, among the more complex signal processing devices in use today, are used for real-time detection of health problems and general diagnostic procedures. Slower than radar and faster than sonar, ultrasound systems have become increasingly portable, evolving from cart-based systems into palm-sized devices. This article discusses some of the necessary ingredients of compactness.

Reducing Ground Bounce in DC-to-DC Converters—Some Grounding Essentials - June 2007

Electrical ground looks simple on a schematic, but circuit performance is dictated by the PCB layout. Ground-node analysis is difficult, especially for dc-to-dc converters, such as buck and boost circuits, which pound the ground node with large, fast-changing currents. When ground moves, performance suffers and the system radiates EMI. An understanding of ground noise can provide a sense for reducing the problem.

Low-Dropout Regulators (Ask The Applications Engineer—37) - May 2007

Voltage regulators provide stable outputs independent of line voltage, load impedance, temperature, and time. Low-dropout regulators (LDOs) can maintain regulation with a small difference between supply voltage and load voltage. This article introduces basic topologies of LDOs, and provides tips for ensuring stable operation. It also discusses ADI's LDOs, which offer a flexible approach to maintaining dc- and dynamic stability.

Elements of Motion: 3D Sensors in Intuitive Game Design - April 2007

Standard video game controllers limit intuitive play, requiring a player to learn specific control skills. The latest platforms add motion, enabling games that are both more fun and more intuitive. This article presents a foundation for using accelerometers in game controllers, including operating mechanisms, measurement techniques, and specific parameters that affect gaming performance, price, reliability, verification, and test.

High-Speed Time-Domain Measurements—Practical Tips for Improvement - March 2007

Making accurate high-speed time domain measurements can be challenging, but a few tips and tricks, coupled with some good old-fashioned commonsense engineering, can help yield quick and accurate results. When choosing a scope and probe for high-speed measurement, first consider: signal amplitude, source impedance, rise time, and bandwidth. The type of probe and length of the ground lead are also important.

Wideband ADC Front-End Design: Amplifier Drive vs. Transformer Drive (Ask The Applications Engineer—36) - February 2007

The circuitry ahead of a high-performance ADC is critical to achieving desired system performance. The optimal design depends on many factors, including the application, system partition, and ADC architecture. Amplifiers consume power and add noise, whereas transformers consume no power and add negligible noise. On the other hand, amplifiers maintain dc levels, provide easily adjustable gain, and have flatter response.

Multichannel Power-Line Monitoring with Simultaneous-Sampling ADCs - January 2007

The rapid expansion of the electric power industry has created a worldwide need to reinforce existing transmission and distribution networks and to construct new substations. Advances in microprocessor technology and the increasing cost of support staff are key drivers for power companies to design new automated high-voltage substations using high-accuracy integrated automation systems.

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