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Power MOSFET Chip Set Optimized For Each Part of DC/DC Circuit Set To Power Next Generation of Notebook Microprocessors
New Vishay Siliconix Devices Are Tailored To Switching MOSFET and Synchronous Rectifier Slots for Power Conversion Designs
MALVERN, PENNSYLVANIA - September 22, 1999 - Anticipating the next generation of mobile microprocessors, a power MOSFET chip set that greatly improves the efficiency of dc-to-dc conversion circuits in notebook PCs was released today by Vishay Intertechnology. Consisting of devices that are individually optimized for switching and synchronous rectification functions - as performed by the two MOSFETs in a dc-to-dc circuit - the new Vishay Siliconix chip set works with popular controller ICs from Vishay Siliconix and other suppliers to deliver improvements in efficiency on the order of 5% compared to previous state-of-the-art power MOSFET devices.
"Vishay Siliconix was the first to recognize the need for power MOSFETs specifically designed for power conversion circuits," said Evan Lambka, Product Marketing Manager at Vishay Siliconix. "With this new chip set, we've gone beyond optimizing for power conversion in general and have optimized these MOSFETs according to whether they will be used in the upper or lower slots in the dc-to-dc circuit."
In addition to lower conduction losses, the devices feature fast switching speeds for more efficient operation, with typical turn-on times as low as 3 ns.
The chip set consists of the Si4874DY, a 7.5-milliohm device with 35-nC gate charge, and the Si4884DY, a 10.5-milliohm device with 15.3-nC gate charge. The Si4874DY provides the low on-resistance required for the bottom freewheeling MOSFET, which carries the current for the majority of the time, and is designed to withstand fast switching transients. For the upper MOSFET slot in the same circuit, the Si4884DY provides the fast switching times that are critical for the switching FET role, with a lower level of gate charge that is ideally suited to the shorter duty cycle of the upper position.
The product of gate charge multiplied by on-resistance provides a general figure of merit for devices that will be used for switching at high frequencies. For this new chip set, this figure is 252 for the Si4884DY, a record for any device with comparable specifications. In a converter with a 15-A output and a VOUT of 2 V - which will be typical requirements for powering the next generation of microprocessors - this chip set delivers 83% efficiency, and 95% at 3A output.
"As CPUs get faster and faster, meeting their power specifications will be increasingly difficult," Lambka added. "The Si4874DY/Si4884DY combination could make the difference as to whether a 500-MHz notebook is feasible or not."
Samples and production quantities of the Si4884DY/Si4874DY chip set are available now, with lead times of 6 to 8 weeks for larger orders.
Vishay Intertechnology, Inc., a Fortune 1000 Company listed on the NYSE (VSH), is one of the world's largest manufacturers
of discrete semiconductors (diodes, MOSFETs, and infrared optoelectronics) and passive electronic components (resistors, inductors,
and capacitors). These components are used in virtually all types of electronic devices and equipment, in the industrial,
computing, automotive, consumer, telecommunications, military, aerospace, power supplies, and medical markets. Vishay’s product
innovations, successful acquisition strategy, and "one-stop shop" service have made it a global industry leader. Vishay can
be found on the Internet at www.vishay.com.