Electronic Design

Thermally Enhanced MOSFET Line Gets A Breakdown-Voltage Boost

Applications that often require MOSFETs with 200-V breakdown ratings include high-powered (up to 1000-W) class D audio amps, 48-V output ac-dc supplies (for synchronous rectification), brushless dc-motor drives (up to 1 hp), and isolated dc-dc converters operating from a universal input range (36 to 75 V). To deal with those applications, International Rectifier s first DirectFET-packaged MOSFET offers a 200-V breakdown voltage rating. Previous DirectFET MOSFETs offered a maximum breakdown voltage of 150 V.

IR introduced the DirectFET package in 2002. In the DirectFET, solderable pads on the chip enable the die to be directly attached to a pc board for bottom-side cooling. At the same time, a copper drain clip on the top of the package permits top-side cooling.

The advantage of the proprietary DirectFET package is low thermal resistance between the die and the top and bottom of the package. In the case of the new IRF6641TRPbF, this makes it possible to design for a case temperature 13°C lower than an equivalent part in an enhanced SO-8 package or to increase power by 33% while running at the same case temperature.

The MOSFET device in the package provides 59.9-mΩ guaranteed-maximum RDS(ON) and 34-nC (typical) gate charge. The package and the chip make a potent combination. In tests, IR ran the IRF6641TRPBF and other enhanced SO-8 devices in the same secondary-side synchronous rectification sockets and measured 0.4% efficiency improvement (95% at 7 A) when single devices were compared. Tests also showed efficiency parity when a single DirectFET part was compared to a pair of devices in separate enhanced SO-8 packages.

The IRF6641TRPbF costs $1.24 each in 10,000-unit lots. The new device comes in the standard MZ dimensions.

International Rectifier

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