El Segundo, Calif—International Rectifier's new DirectFET chipset is designed to maximize DC/DC bus converter efficiency. When used with IR's recently announced IR2086S full-bridge bus-converter IC, the chip set enables a solution that can deliver 336 watts with 97 percent efficiency in a footprint that's about 30 percent smaller than a traditional quarter-brick converter, according to the company.
"IR's new IRF6646 and IRF6635 achieve higher efficiency and operate at about 40°C lower case temperature when compared to SO-8 devices," said Carl Blake, director of Technical Marketing, Computing and Communications Group. 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 percent for each 10 degrees temperature reduction."
The 80-volt IRF6646 and 30-volt IRF6635 are optimized for 48-V regulated and 36-60 volt input bridge topologies in isolated DC/DC bus converters, synchronous-buck (non-isolated) DC/DC topologies, forward and push-pull converters (18-36 volt input) and secondary-side synchronous rectification in regulated DC/DC applications.
Typically, the industry standard, 300-watt 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 percent reduction in power semiconductor part count, according to the company. In addition, isolated bus converter DC/DC applications made with this chip set achieve 29% reduced board space and operate with greater efficiency (up to 1.5 percent).
The IRF6646 has a maximum on-state resistance of 9.5 milliohms, which claims an industry best in this form factor by approximately 37 percent, and is tailored for primary-side bridge topologies. The IRF6635 has a maximum on-state resistance of 1.8 milliohms and is optimized for secondary-side synchronous rectification. The IRF6635 also claims the lowest on-state resistance in this form factor by up to 22 percent. In a standard application, this MOSFET pair combines with the IR2086S full-bridge DC bus converter IC and the existing IRF6608 30-volt DirectFET MOSFET, which is used as a secondary-side gate clamp.
The new DirectFET MOSFETs are supported by myPOWER, IR's online design center, located at www.irf.com/design-center. Device datasheets area available at www.irf.com/product-info/datasheets/data/irf6646.pdf (and -irf6635.pdf).
The IRF6646 is priced at $1.37 each, and $1.50 each for the IRF6635, both in 10k quantities. Prices are subject to change.
International Rectifier, 1-310-252-7105, www.irf.com