Keeping It Lean And Mean

Paul Whytock looks at some of the latest developments in the international power electronics sector.

Taking a look at the lighting side of the power market, International Rectifier introduced its IRS2153D, an electronic ballast IC for fluorescent lamps (Figure 1). In addition to being leadfree, the 600V self-oscillating half-bridge IC includes an internal bootstrap diode to simplify circuits. It’s also designed to increase efficiency and performance over older, less-efficient selfoscillating bipolar transistorbased solutions.

The IRS2153D’s oscillator frequency precision of 3%, helps to optimise external component selection for uniform lamp brightness during manufacturing. A preheat feature, which sets the correct preheat frequency for the correct duration (thus helping to maximise lamp life), can be easily realised externally.

The IC includes 2V undervoltage lockout hysteresis for more robust ballast circuits and prevents unwanted shutdown when there are momentary transients. In addition, an undervoltage lockout circuit ensures that the high-side floating voltage correctly switches the high-side gate driver output.

PoE Device Merges Analogue, Digital, And Power
Switching gears in the everevolving power arena, a joint development between PowerDsine and Freescale has borne fruit with the PD64004A 4-Channel Power over Ethernet PD64004A joins the 12-port PD64012 and other current PD64004 solutions. One particularly smart aspect of this new chip, which uses Freescale’s SMARTMOS8 technology, is that it integrates power, analogue, and advanced digital logic functions into one device. It’s optimised for use in low-port count Ethernet switches, SOHO routers, and midspans, allowing for nextgeneration network devices to share power and data over the same cable.

The chip is designed to minimise the number of external components required and to reduce overall system costs. Capable of operating under a switch ambient temperature range of –40° to +85°C, the PD64004A simplifies the router and switch vendor’s thermal design tasks.

This feature will particularly benefit those industrial systems targeted for industrial use. Moving to 1-Ω sense resistors, the PD64004A reduces total thermal dissipation and eases system design. The chip now supports fully automated operation and power management, eliminating the need for microcontrollers.

Special pins dedicated for total setup allow the device to be truly stand-alone. Up to eight PD64004A managers can cooperate automatically to provide up to 32 ports of PoE at the lowest implementation costs (see "About Power over Ethernet Technology". The device fully complies with the IEEE 802.3af-2003 standard, and works with pre-standard proprietary solutions.

MOSFET driver ICs have flexible gate drive levels
Vishay Intertechnology developed three new high-speed, halfbridge MOSFET driver ICs that provide flexible gate-drive levels. The company claims they will optimise efficiency, reduce component count, and minimise expense in high-frequency, highcurrent, dc-dc synchronous rectifier buck power supplies.

The MOSFET drivers operate with external n-channel MOSFETs. They’re designed to provide gate-drive voltages of 8 or 12V, operate at switching frequencies up to 1 MHz, and function in 5 to 48V systems (e.g., power converters and industrial and computing equipment). The high-side driver of each device features an internal bootstrap component count.

In the SiP41109, the gate-drive voltage is supplied to the high-side driver by an integrated 80-mA, 8V regulator and to the low-side driver by the supply voltage. In the SiP41110, the regulator supplies both high-side and low-side voltages. In this way, designers can choose the gate-drive voltage most suitable for achieving an optimal tradeoff between MOSFET conduction and switching loss for the chosen operating frequency.

Adaptive shoot-through protection in the drivers prevents simultaneous conduction of the external MOSFETs. Undervoltage lockout holds off circuit operation until the supply voltages reach valid operating levels, and overtemperature protection disables the drivers if the die temperature exceeds 165°C.

ESD diode arrays in micro leadframe packages
A series of electrostatic-discharge (ESD) diode arrays in ultra-small micro leadframe packages, designed to protect staticsensitive equipment from damage or degradation caused by overvoltage transients, is the latest arrival from STMicroelectronics.

Thanks to their small size, these devices suit applications such as cellular phones, digital cameras, MP3 players, and many other portable applications, as well as computer and telecom products. Each device in the new series offers ESD protection for between one line and five lines.

The ESDALC6V1M3 is a lowcapacitance device with two ESD diodes integrated in an SOT883 package. It can be used for 1- line or 2-line ESD protection in all types of application. The diode capacitance is around 7pF (VR = 2.5V), suiting it for high-speed data lines or other I/O interfaces. The ultra-small SOT883 has an area of 0.6mm2, saving up to 50% more space than an SOD523 package. For two-line applications, the board-area requirement is only 0.3mm2 per line, which is even smaller than for the 0402 package.

The ESDA(LC)6V1M6 and ESDA(LC)6V1-5M6 are four-line and five-line ESD diode arrays in a micro leadframe package (Micro QFN). Two levels of diode capacitance are available to meet different application requirements in terms of data rate, power dissipation, and other criteria; the capacitance is less than 7pF (VR = 2.5V) for the ESDALC6V1xxM6 series, and is 41pF (VR = 2.5V) for the ESDA6V1xxM6 series. The Micro QFN-6L is the smallest plastic package on the market for an ESD array of up to five diodes—its 1.45mm-by-1.0mm size saves 44% more space than the current SOT666.

Free online design tool for op amps
Intersil unleashed a free, interactive, web-based tool for selecting and simulating devices from the company’s op-amp portfolio. Called iSim, it will allow users to verify their design’s stability without breadboarding.

Based on input and output specifications provided by the user, iSim will find all suitable Intersil devices for a given application. In many cases, simulation is also available for immediate feedback on circuit performance.

The iSim design suite provides dynamic input fields to enter input and output requirements. The company says its selection of configurations fulfills design needs quickly and efficiently.

The iSim simulator tool integrates an applications-based Intersil analogue-signal-processing solution selector with dynamic input fields to match a designer’s input and output requirements.

Schottky barrier rectifiers are based on trench MOS technology
Vishay Intertechnology launched what it claims are the first Schottky barrier rectifiers based on trench MOS technology. Useful as a rectification circuit or ORing diode in redundant switch-mode power supplies, or to replace synchronous rectification solutions, the five new devices feature the lowest forward- voltage drop among Schottky rectifiers for their package types, says the company.

Packaged in a TO-220AB case that’s rated for 40 A (2 X 20 A) and 100 V (claimed as a first), the VTS40100CT is optimised for 100- to 300-W, high-frequency, switch-mode power-supply applications. Its ultra-low typical forward- voltage drop of 0.375V at 5A and 125°C reduces conduction power losses. The VTS40100CT can also improve ORing diode efficiency in the high-voltage output of redundant switch-mode power supplies.

The new V40100P is also rated for 40 A (2 X 20 A) and 100 V, with a TO-247AD case and an even lower typical forward-voltage drop of 0.372 V under the same conditions. That forward-voltage drop is matched by the V50100P, which features a TO-247AD case as well. It has an even higher rating of 50 A (2 X 25 A).

The V30100S and VF30100S are both rated for 30 A (1 X 30 A) and 100 V.

Micro-power op amps
Texas Instruments completed work on a brand new family of precision, micropower op amps from the company’s Burr-Brown product line. The OPA379 family operates within a 1.8 to 5.5V supply voltage range. It features high-performance, single-supply operation, very low quiescent current (2.9mA), and low noise (80nV/√Hz) relative to the quiescent current. The micro-size packages suit the devices well for battery-powered applications.

White LED Drivers Eye New Colour LCD Panels For Portables
Toshiba Electronics Europe expanded its constant-current white LED-driver product line with a compact dc-dc converter IC for powering multi-segment white LEDs (Figure 2). These drivers are used to backlight new, larger colour LCD panels in small portable devices, including cell phones and PDAs. A single device drives from two to eight LEDs in series. High output power allows for up to 800mW LED loading.

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