EL SEGUNDO, CA. July 1996 - International Rectifier (IR) now offers power supply designers a complete design specification for a Voltage Regulator Module (VRM) to power next- generation microprocessors such as Intel's Pentium Pro^TM. This specification, designated the IRP6VRM1, includes a complete DC/DC converter design based on a synchronous buck regulator topology, along with a full bill-of-materials, schematic and PCB layout in Gerber format. It is intended to shorten the design cycle for mP power supplies by eliminating the tedious task of component selection and evaluation.

"This is another example of IR's commitment to supply customers with total power system solutions, rather than just discrete power components," said Chris Davis, product marketing manager at IR.

"It mirrors the effort we made for customers with our recent powIRtrain power solutions for motor drives, in that it provides a complete solution to designers for a very complex product. This allows them to get up the power component technology curve much faster, and get new more efficient designs based on the latest power components to market faster. Our specification also allows them to adapt our suggested design for their packaging requirements and manufacturing processes," he noted.

The IRP6VRM1 specification is for a DC/DC converter that accepts a 5-V or 12-V input and provides a digitally selectable 2.0-to-3.5-V output with continuous current rated up to 13 A. An efficiency in excess of 90 percent is achieved, while offering a transient response of greater than 30 A/ms and an output ripple voltage of well within the +/-1% tolerance specification. This one single design is capable of powering a wide range of microprocessors from the Intel 150MHz Pentium Pro^TM up to the new 266 MHz Klamath processor. The same design can be used in VRM for m or embedded on the mother board to reduce cost.

The excellent performance characteristics achieved by the synchronous buck regulator topology operating at about 200 kHz accrues from IR's Generation 5 HEXFETs and new FETKY ^TM.

"The IRL3103D1S FETKY^TM is the industry's first MOSFET and Schottky rectifier co-packaged in the popular D2Pak," says Davis. "It is designed specifically to offer a cost-effective, high-performance solution as a synchronous rectifier for this application."

Davis noted that IR's advanced Generation 5 process allows for a reduction in chip size, while still reducing RDS(on) for MOSFETs. This reduction in chip footprint makes space available in the same package to include a low-drop Schottky rectifier for a multi-chip solution, while achieving excellent performance. By co-packaging the devices, footprint and assembly costs are reduced. In addition, the stray inductance between the two devices is cut significantly.

Davis said that "When using an external discrete Schottky for synchronous rectifier applications, overall system performance suffers. The inductance associated with the leads and board layout delays the turn-on of the Schottky, forcing the current through the FET's inefficient integral diode."

The FETKY^TM configuration reduces this stray inductance dramatically from about 12nH for a typical discrete to only 3.5nH minimizing the integral diode conduction and improving performance. The IRL3103D1S offers a 30-V, 0.014-ohm n-channel MOSFET which can be driven from a VGS gate drive of 4.5 to 10 V. The Schottky offers a 0.42-V forward voltage drop at 1 A. The IRL3103S is used as the upper control device offering the same MOSFET ratings (30-V, 0.014-ohm, n-channel, D2Pak) as the FETKY^TM. Both part numbers are available in the standard through-hole TO-220 package style by removing the "S" suffix.

The IRP6VRM1 turnkey design specification offers complete performance characterization of the DC/DC converter along with the full bill-of-materials, schematic, and printed circuit board layout (in Gerber format). Evaluation kits (the IRP6VRM1-EV) are available. The evaluation kit includes the design specification, evaluation board, and samples direct from the company of the IRL3103S control switch and IRL3103D1S FETKY^TM synchronous rectifier. IR is not intending to manufacture the voltage regulator module (VRM). Data sheets for the turnkey specification, power MOSFET, and FETKY^TM are available through IR's web site (http://www.irf.com) and Fax-On-Demand system (310-252-7100 in US, 44-1883-733-420 in UK).

For more information access the Design Specification on-line or directly access the Design Package.