EL SEGUNDO, CA. December 2000 - International Rectifier (NYSE: IRF) has introduced a new series of topology-specific HEXFET^® power MOSFETs that maximize efficiency in targeted isolated and buck DC-DC converters. As DC-DC converter output voltages approach the one-volt mark, IR's MOSFETs increase efficiency by up to one percent, compared to the same circuits using industry-best devices.

IR's new 100V-rated IRF7473 in an SO-8 package has been designed for the primary stage of two-stage isolated converters with 48V input, 1.6V output at 60A. The IRF7473 is optimized for low device on-resistance and low gate charge, and improves efficiency by 0.4% compared to the best-in-class competitor. Peak efficiency ratings as high as 90% can be achieved when the IRF7473 is matched with the new IRF7822 synchronous rectification MOSFET. See figure 1 for efficiency curves. The IRF7473 can also be used in a full bridge configuration.

IR's new 40V-rated HEXFET MOSFETs in the SO-8 package are designed to work with a 28V bus in notebook computers. In fact, some manufacturers are increasing the number of cells in notebook batteries, lifting the bus voltage to 28V. The raw battery voltage is distributed through the system in a power plane, and is point-of-load (POL) regulated down to the required voltage. Traditional 30V-rated MOSFETs are no longer sufficient for this application, and a 40V rating is required to fully protect the power system from voltage spikes. IR's new 40V-rated devices offer designers a choice between two control MOSFETs, the IRF7468 and the IRF7469, and two synchronous MOSFETs, the IRF7470 and the IRF7471. Synchronous buck topologies using the IRF7468 and IRF7470 reach an efficiency of 82% in 28V input, 1.3V output converters running at 300KHz.

Figure 1. Efficiency in a two-stage isolated converter using the IRF7473 and the IRF7822.

Four additional MOSFETs (IRF7453, IRF7450, IRF7451 and IRF5801) are optimized for significantly reduced on-resistance, while keeping gate charge to a minimum level. The MOSFET quartet have been optimized for 48V input, active and passive reset, primary-side isolated DC-DC converters below 30W.

A specification summary for the new topology-specific MOSFETs appears in Table 1.

Part Number	Package	VDS	VGS	ID	RDS(on) @10V	Typ. Application
IRF7473	SO-8	100V	20V	6.8A	26mOhms	Primary, 48Vin 2-stage or full bridge
IRF7468	SO-8	40V	12V	9.4A	15.5mOhms	Buck, control FET, 24V bus
IRF7469	SO-8	40V	20V	9.0A	17mOhms	Buck, control FET, 24V bus
IRF7470	SO-8	40V	12V	11A	13mOhms	Buck, sync FET, 24V bus
IRF7471	SO-8	40V	20V	10A	13mOhms	Buck, sync FET, 24V bus
IRF7453	SO-8	250V	30V	2.2A	230mOhms	Primary, passive reset, 48Vin
IRF7450	SO-8	200V	30V	2.5A	170mOhms	Primary, passive reset, 48Vin
IRF7451	SO-8	150V	30V	3.6A	90mOhms	Primary, active clamp reset, 48Vin
IRF5801	TSOP-6	200V	30V	0.6A	2.5W	Primary, passive reset, 48Vin

Pricing and Availability

Samples for the new devices are available now, with production quantities to follow in December 2000. Pricing for IR's new MOSFETs begins at US $0.42 each in 10,000-unit quantities.