Sensor Interface Design Demystified

With the rapid expansion of available sensor elements driven by the growth of MEMS (microelectromechanical systems) sensors, the considerations of sensor interface design become ever more important. The design engineer needs to understand both the sensor as well as the application in order to make the proper design tradeoffs in this already tricky art of analog front-end design. The challenge is further compounded with the trend toward MEMS technologies and their inherently smaller signals. This article attempts to cover some of the basics of sensor interface design and gives a cursory overview of the challenges and trade-offs of the possible approaches. It's Not Just a Resistor Fundamentally, every sensor can be modeled as a simpler component, albeit a component with a value that changes over time. Usually this means we can treat them as either a simple passive impedance, such as a resistance, capacitance, or inductance, or as an active source, such as a current or voltage source. As these values change with time, we need to be able to convert that change into a time-varying voltage. Furthermore, we need to maintain the linearity of the sensor while we do this.
Posted in: Articles, Articles, Electronics & Computers, Design processes, Architecture, Microelectricmechanical device, Sensors and actuators

Advanced Ceramic Heaters Improve IC Packaging and System Performance

The continuous increase in the consumption of semiconductor devices and the emergence of new applications in optical components — MEMS, LCD display, flip-chip, chip-onglass, and multichip modules — has created a vast demand for faster throughput and better die-bonding equipment for IC packaging. IC packaging requires a typical ramp rate of 100ºC per second to 400 to 500ºC ±2°C, and a cycle time of 7 to 15 seconds. Similarly, IC chip testing, which stresses chips between -40 to 125ºC while monitoring electrical parameters, also requires a faster cycle rate. To manufacture ICs of all types, a die bonder or die attach equipment is used to attach the die to the die pad or die cavity of the package's support structure. The two most common processes for attaching the die to the die pad or substrate are adhesive die attach and eutectic die attach. In adhesive die attach, adhesives such as epoxy, polyimide, and Ag-filled glass frit are used to attach the die. Eutectic die attach uses a eutectic alloy. Au-Si eutectic, one commonly used alloy, has a liquidous temperature of 370ºC, while another alloy, Au-Sn, has a liquidous temperature of 280ºC.

Posted in: Articles, Articles, Electronics & Computers, Semiconductor devices, Joining, Ceramics

Accelerated Testing — Raising the Bar on Electronics Integrity

By now, most test engineers have recognized that both HALT (Highly Accelerated Life Testing) and HASS (Highly Accelerated Stress Screening) are the fastest and most effective new methodologies for quickly passing design verification and testing (DVT), and the most effective production screenings. Leaders across a broad range of industries have now embraced accelerated testing as a strategic move that can increase competitiveness and improve market share..

Posted in: Articles, Articles, Electronics & Computers, Electronic equipment, Systems engineering, Production, Quality control, Test procedures

High-Integrity Java Targets Safety-Critical Systems

High-integrity software plays critical roles in telecommunications, transportation, defense systems, industrial automation, and power management. Because human lives may be lost and tremendous economic costs may result if the software fails, the development of high-integrity software adopts practices that impose greater rigor on the software development processes. This rigor includes documentation of system requirements, architecture, design, test plan, and source code; development accountability audit trails; independent peer review of all development artifacts; full traceability analysis; and extensive test coverage. The goal of this increased rigor is to assure correct operation and reliability of the software. As computer automation expands its reach and influence, the size and complexity of high-integrity software is expanding as well. To deal with the increased development workload resulting from the ever-expanding role of high-integrity software, military and aerospace industries are leading the way towards the use of a safety-critical subset of the Java programming language to help increase developer productivity and reduce the maintenance costs associated with highintegrity software.

Posted in: Application Briefs, Application Briefs, Electronics & Computers, Computer software / hardware, Safety critical systems, Productivity, Quality control

Multi-Fabric Switching Enables New Architectures for Military Systems

With multiple switched interconnects gaining momentum in the embedded space, selecting just one to address a wide range of military systems requirements is not easy.

Individually, switched fabrics such as Gigabit Ethernet (GbE), Serial RapidIO (SRIO), and PCI Express (PCIe) have their own particular technical merits, and each is poised to carve out a piece of the interconnect market. However, when combined in nextgeneration Serial Switched Backplanes (SSB) like VPX (VITA 46/48), multi-fabric switching can enable powerful new military architectures by leveraging 'best of breed' interconnect technology to address specific application requirements ( Figure 1).

Posted in: Articles, Articles, Electronics & Computers, Architecture, Embedded software, Switches, Military vehicles and equipment

Multicores Affect Algorithm Choices

Design engineers soon will need to bridge the growing gap between hardware reality and software capabilities in the highperformance computing (HPC) realm as the use of multicore microprocessors grows. If your software development or sourcing plans haven't anticipated these development situations, your applications may have a shorter life than you had planned.

The 2006 version of technical computing "reality" is an inexpensive dual-core processor from AMD or Intel on a desktop system, or a dual- or quad-core RISC processor from Sun or IBM running on a server. In 2007, we should expect to see inexpensive quad-core processors from AMD and Intel, and processors with up to eight or more cores in 2008. These small symmetric multiprocessing (SMP) systems will be a far cry from the proprietary $500,000+ SMP systems of a few years ago. This technology transition has big implications for the "democratization" of computing power. On the horizon are four- to eightcore systems that cost only a few thousand dollars and sit on the desk of every design engineer.

Posted in: Application Briefs, Application Briefs, Electronics & Computers, Mathematical models, Computer software / hardware, Systems engineering

Embedded Databases: Data Management for Real-Time and Embedded Systems

The term embedded database was coined in the 1980s to mean a database management system (DBMS) that is embedded into an application, in contrast to large central databases (nowadays, usually client/server DMBSs a la Oracle). The first embedded databases had little or nothing to do with embedded systems, which were largely 8-bit, or possibly 16-bit, devices that performed a very specific function. Any data processing requirements were promoted to a higher layer in the system architecture. Embedded systems, like all other facets of computing, have matured and gained faster (32-bit) processors, memory, and more complexity. This has further confused conversations about embedded systems and embedded databases. Today, the term embedded database encompasses databases embedded into software applications, as well as the more modern client/server database design (although embedded client/several varieties are much smaller than their enterprise-level DBMS cousins such as Oracle or DB2). In fact, while embedded databases comprise a sizeable chunk of the overall database market, they show remarkable diversity in important respects such as programming interfaces, storage modes, and system architecture. This article examines some of these differences to help in choosing the right embedded database system for a given project.

Posted in: Articles, Articles, Embedded Technology, Board-Level Electronics, Electronics & Computers, Software, Architecture, Embedded software, Data management