EL SEGUNDO, Calif. - June 2005 - International Rectifier, IR® (NYSE: IRF), a world leader in power management technology, today introduced a new DirectFET® chipset that maximizes DC bus converter efficiency, when used with IR's recently announced IR2086S full-bridge bus converter IC. The chip set enables a bus converter solution capable of delivering 336W with 97% efficiency in a footprint 29% smaller than a "quarter-brick" converter.

The IRF6646 and IRF6635 are optimized for 48V regulated and 36V to 60V input bridge topologies in isolated DC-DC bus converters, synchronous buck non-isolated DC-DC topologies, 18V to 36V input forward and push-pull converters for mobile communication, and secondary-side synchronous rectification in regulated output isolated DC-DC applications.

A typical industry standard, 300W quarter-brick contains as many as ten MOSFETs (four in the primary-side and six in the secondary-side), a pulse width-modulated (PWM) IC and two half-bridge driver ICs. IR's new chip set solution consists of six MOSFETs (four in the primary and two in the secondary side) and a single IC, yielding a 46% reduction in power semiconductor part count. In addition, isolated bus converter DC-DC applications made with this chip set achieve 29% reduced board space and operate with as much as 1.5% better efficiency.

The new IRF6646 80V MOSFET has a maximum on-state resistance of 9.5mOhms, which sets an industry best in this form factor by approximately 37%, and is tailored for primary-side bridge topologies, while the IRF6635 30V MOSFET has a maximum on-state resistance of 1.8mOhms and is optimized for secondary-side synchronous rectification. The IRF6635 also achieves the lowest on-state resistance in this form factor by up to 22%. This MOSFET pair combines with the recently-introduced IR2086S full-bridge DC bus converter IC and the existing IRF6608 30V DirectFET MOSFET, used as a secondary-side gate clamp.

"IR's new IRF6646 and IRF6635 achieve higher efficiency and operate at about 40 degrees Celsius lower case temperature when compared to SO-8 devices. Device temperatures have a direct impact on overall failures-in-time (FIT) rates and mean time between failures (MTBF), since temperature is a first-order parameter in these calculations. In general, failure rate is reduced by 50% for each 10 degrees temperature reduction," said Carl Blake, Director of Technical Marketing, Computing and Communications group.

Part Number	Package	VDSS	RDS(on) max @ VGS=10V	Qg typical	Qgd typical
IRF6646	DirectFET®Medium MN	80V	9.5mOhm	36nC	12nC
IRF6635	DirectFET®Medium MX	30V	1.8mOhm	47nC	17nC

Design Support

The new 80V and 30V DirectFET MOSFETs are supported by myPOWER, IR's online design center

In addition, the following application notes will be useful in learning more about DirectFET packaging technology:

• AN-1035: Board Mounting Guidelines for DirectFET MOSFETs
• AN-1050: Materials & Practices for DirectFET MOSFETs
• AN-1059: Thermal Modeling and Characterization for DirectFET MOSFETs

Patented DirectFET® Packaging Technology

International Rectifier's patented DirectFET MOSFET packages present a whole new set of design advantages not previously delivered by standard plastic discrete packages. Their metal can construction enables dual-side cooling that effectively doubles the current handling capacity of high frequency DC-DC buck converters powering advanced microprocessors. In addition, devices in the DirectFET package are RoHs compliant containing no lead or bromide.

For more information related to DirectFET MOSFET Packaging Technology visit the DirectFET Home page.

Availability and Pricing

The new 80V IRF6646 and the 30V IRF6635 DirectFET MOSFET synchronous buck chip set is available immediately. Pricing is US $1.37 each for the IRF6646 and US $1.50 each for the IRF6635, both in 10,000-unit quantities. Prices are subject to change.

Patent and Trademark Notice

IR's proprietary DirectFET technology is covered by US Patents 6624522, 6784540 and multiple other US and foreign pending patent applications. DirectFET® is a trademark of International Rectifier Corporation. IR® and HEXFET® are registered trademarks of International Rectifier Corporation. All other product names noted herein may be trademarks of their respective holders.