EL SEGUNDO, CA. December 2000 - International Rectifier (NYSE: IRF) has introduced two new HEXFET^® power MOSFETs, IRF7811W and IRF7822, that deliver up to 3% efficiency increase in buck and isolated DC-DC topologies. By choosing the most suitable manufacturing process for a specific application, IR's technology toolbox provides industry-leading solutions to challenges faced by the design engineer. These two application-specific MOSFETs are manufactured using a new stripe trench process and follow the introduction of the benchmark planar devices introduced earlier this year.

"The advantage of the new process is the decoupling of device on-resistance and capacitance, parameters that are historically a trade-off in power MOSFETs. As a result, devices with both extremely low device on-resistance and very low gate charge are now possible, the best of both worlds," says Carl Blake, Technical Marketing Manager.

As DC-DC circuit output voltages approach the one-volt mark, operating currents also increase. Today's high-end notebook computers consume 20A, requiring several MOSFETs in parallel. Servers and high-end desktop computers presently require 60 to 90A, and often use a multi-phase DC-DC topology. The next-generation GHz class of microprocessors will require even more current. These changes in operating conditions challenge power components to maintain acceptable converter efficiency levels.

Blake continues, "In these high current buck converter topologies, the IRF7811W control FET and the IRF7822 synchronous FET can decrease parts count from 25 to 50% while maintaining the same efficiency level, compared to the industry-best solution. The performance advantage of these parts can be used to run DC-DC converters at a lower temperature or increase power density in the same form-factor."

Part Number	Package	VDS	VGS	ID	QG typ.	RDS(on) typ. @4.5V	Typ. Application
IRF7811W	SO-8	30V	12V	14A	18nC	9mOhms	Control FET or sync FET in smaller DC-DC
IRF7822	SO-8	30V	12V	18A	44nC	5mOhms	Sync FET

In a multi-phase buck converter with an input voltage of 12V and output voltage of 1.4V, operated at 700KHz per leg, a gain in efficiency of more than 3% has been achieved when compared to the previous best solution with a reduction in part count. The output current of 35A per leg using SO-8-packaged MOSFETs has been made possible using two IRF7822 in parallel as synchronous FETs and two IRF7811W as control FETs. See figure 1.

Figure 1.
• Over 3% efficiency gain with the new IRF7811W or IRF7822
• Up to 50% reduced part count with the new IRF7822

Isolated converters used in the telecom and networking industry use either self- or IC-driven topologies to drive the secondary stage MOSFETs. In both topologies, the output voltage may be as low as 1.5V to power the next generation of broadband equipment, where the ASIC is expected to operate at this low voltage. Under these conditions, synchronous rectification is necessary to reduce power dissipation and maintain required efficiency. IR's new MOSFETs provide the most efficient solution in the industry today. Depending on power level, efficiency target and circuit design, manufacturers can choose either the IRF7811W or the IRF7822.

In a self-driven two-stage isolated converter, an efficiency gain of more than 1% has been achieved by replacing the previous-best MOSFET in the secondary stage with an IRF7822. The new IR device enables efficiency to 85% in 48V input, 1.6V, 60A output conversion at full load.

IC-driven topology, isolated converters can achieve industry best efficiency of 85% at 40A and 1.5V output using IR's new IRF7822 synchronous MOSFET and the IR1176 synchronous rectification IC (SRIC). This chipset enables benchmark performance in simplified forward topology circuits.

Pricing and Availability

Samples for the new IRF7811W and IRF7822 MOSFETs will be available in December 2000, with production quantities to follow in February 2001. Pricing begins at US $1.27 each in 10,000 unit quantities.