Keeping Pace With Designer Demands

Paul Whytock introduces the first edition of Power Design Europe, a sister publication to Electronic Design Europe.

Europe's power system design engineers have a constant working brief to ensure the designs they create and the components they specify are capable of performing at optimum levels regarding power efficiency, management and conversion. To meet these design demands it is essential the power electronics industry continues to exploit the new advantages that semiconductor technology provides.

In this first edition of Power Design Europe, we look at a comprehensive range of technologies, many of which are targeted at applications that demand low power and highly efficient performance.

Silicon on Insulator (SoI) fabrication technology an example. This semiconductor development allows high voltage transistors to be cost-effectively fabricated on the same substrate as low voltage circuitry, such as decoder logic. As a result single chip, high voltage motor driver ICs designs are now possible. It will also allow induction motors to permeate a wider range of applications, including low-cost products that previously would not warrant such sophisticated motor technology.

Conventional bulk silicon fabrication technology forces designers to use junction isolation to isolate individual circuit elements. But devices such as forward biased diodes and minority carrier injection devices cannot then be integrated on the same substrate as a high voltage power transistor, such as an IGBT or power MOSFET.

PERFECT INSULATOR
In contrast, high voltage SoI fabrication allows the various circuit elements to be isolated by a thin layer of silicon dioxide, which is a perfect insulator. Not only does this allow almost any type of active device to be integrated alongside power transistors rated up to 500V or higher, but it also allows all devices to be packed together very densely on the substrate. Leakage currents are also greatly reduced, as are parasitic effects. By comparison, junction isolation techniques introduce parasitic capacitances and do not prevent leakage currents from flowing.

Recent technical developments have also made available a 3-phase motor controller that integrates all the circuitry required to control six power NMOS FETs for fractional horsepower motors up to 50 V. The basic techniques of fixed off-time PWM current control and bootstrapped high-side gate drives are enhanced by adding synchronous rectification control, cross-conduction protection and on-chip charge pumps to allow 100% PWM duty cycles. Safety features and diagnostic output prevent inappropriate switching of the power FETs and allow programmable motor spin-down on power loss.

However, as crucial as technical developments are to any given market, its progress relies on other factors as well. Standardisation is critical and we look at how two companies have created an alliance to ensure future DC/DC product compatibility and standardisation are cohesive.

It is also a fact that no industry sector survives without the development and launch of new products. To this end Rohm has expanded its family of surface mount power MOSFETs with a range of ultra-miniature devices that have on resistance ratings as low as 35mOhm and that handle currents up to 3.5A.

Suited to power management applications in portable equipment, the devices are supplied in Rohm's TUMT packaging. These have footprints of 2.0mm x 1.7mm. A board mounting profile of 0.85mm is 25% lower than previous UMT (SOT323/363) style devices, while power dissipation ratings of 500mW represent a 150% increase over UMT alternatives, claims the company.

In the motor control arena, Toshiba has expanded its technical offering with a brushless motor driver IC that provides a 2A output current. The TPD4104K uses Toshiba's high-voltage pulse width modulation (PWM) control technology and is expected to reduce motor drive development time, save board space and minimise component count.

One aspect of this new device is that it accepts logic signals from the MPU or motor controller and will drive up to 2A through integrated IGBT outputs.

PREDICTIVE GATE DRIVE TECHNOLOGY
Texas instruments has been building on its TPS40K line of DC/DC controllers, with the announcement of two new highly efficient, synchronous DC/DC buck controllers that support input voltages from 4.5 to 28V. They employ TI's Predictive Gate Drive technology to achieve up to 96% power efficiency and ease circuit design in non-isolated power systems in networking, telecom, wireless base stations and computer server applications. The thing about Predictive Gate Drive technology is it minimises diode conduction losses associated with the high-side and synchronous rectifier N-channel MOSFET transitions.

The TPS40070 and TPS40071 single-chip devices provide under voltage lockout, soft-start and high-side short-circuit protection. Each device has programmable fixed frequency up to 1 MHz and voltage feed forward to provide greater line regulation over the entire input voltage range

On the conversion side of the power electronics business C&D Technologies has introduced a series of standard open-frame quarter brick converters capable of delivering up to 40A at voltages as low as 1.0VDC. Efficiency levels are up to 91%.

Fast becoming a green machine, National Semiconductor has decided to get the lead out and to offer lead-free packages for its complete product portfolio by end of 2004. It says that 90% of its products already available lead-free as part of its global effort to protect the environment and replace more than five tons of lead per year. The company has also promised to cut bromine and antimony-based flame-retardants use.

Ultimate Renaissance has added dual and triple output variants to its extremely compact CFM series of open frame 40W AC-DC power supplies. The CFM40D/T supplies have a footprint of only 101.6mm x 50.8mm (4 x 2in) with a height of 30.48mm (1.2in). Efficiency is up to 75% and it has an operating temperature range from 0°C to 50°C.

Efficiency is a key design element in a new range of step-down DC-DC converters from Maxim Integrated Products. These devices are for driving the linear power amplifier (PA) used in cdmaOne and WCDMA cellular phones. The high-speed MAX8506/MAX8507 vary their output voltage from 0.4V to 3.4V in less than 30 microseconds thereby adjusting the power applied to the PA. The important thing here is that this tracking of the transmit power improves efficiency up to 47% at +10dBm.

Two new synchronous-buck MOSFET driver ICs designed for high-current multiphase power solutions have been developed by Intersil Corporation. The Endura(dot) ISL6612 and ISL6613 driver ICs offer 2MHz switching with up to 3A drive current.

Their pre-enable protection is said to be the industry's first to protect against over-voltage such as upper FET shorts before the IC is actually really up and running. This prevents the load voltage from rising to dangerous levels.

See associated figure 1

See associated figure 1


See associated figure 1

TAGS: Components
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