National Semiconductor Introduces Fastest Responding DC/DC Converter for Next-Generation Microprocessors

LM2639 Enables the Smallest Surface Mount Power Supply Solution Available with 70 Percent Volume Reduction

June 15, 1999 ? National Semiconductor Corporation? (NYSE: NSM) today announced the LM2639, a multi-phase pulse width modulation (PWM) controller that provides the smallest power supply solution available for high-end desktop computers, workstations and servers using high-performance microprocessors such as Cyrix M II?, Pentium? II, Pentium III, Merced and K7?. The LM2639 meets the 20A/microsecond load transient demands of next-generation processors. The LM2639?s error amplifier is a transconductance amplifier that achieves the fastest possible response in all transient conditions. For loads greater than 40A for the next-generation of high-end processors such as K7 and Merced, the multiphase topology of the LM2639 offers the smallest and most cost-effective power supply solution.

?With the LM2639, we?re providing designers of servers, workstations and desktop PCs a power supply solution that solves the problems associated with traditional single-phase supplies, such as heat dissipation and size,? said Sonia Ramirez, product manager for National?s power management product line. ?Compared to a conventional single-phase DC/DC converter, the LM2639 offers a power supply solution that enables a 70 percent reduction in board-required volume.?

Unlike a conventional single-phase controller, the LM2639 can distribute current load across up to four converter channels, reducing the heat and stress on the output stage components and eliminating the need for heat sinks. The power channels are also out of phase, which reduces input and output current ripple, and allows for reduced input and output capacitor size. In addition, due to the LM2639?s nominal operating frequency of 8MHz, the size of the output inductors can be greatly reduced, allowing for a much faster load transient response and a dramatically reduced output capacitor bank. The LM2639 eliminates the need for large, costly low-ESR capacitors and enables a 100 percent surface mount power supply design, requiring less than one-third inch in height above the PC board (including magnetics).

The LM2639 provides drive for selectable two-, three- or four-phase operation. It also provides input under-voltage lockout with hysteresis and input over-current protection.

Price and Availability
The LM2639 is priced at $2.50 in quantities of 1000. It will be available in production quantities in June 1999. For more information on the LM2639, visit National?s web site at http://www.national.com/pf/LM/LM2639.html.

About National
National Semiconductor provides system-on-a-chip solutions for the information age. Combining real-world analog and state-of the-art digital technology, the company's chips lead many sectors of the personal computer, communications and consumer markets. With headquarters in Santa Clara, Calif., National has annual of $2 billion and 11,500 employees worldwide. Additional company and product information is available on the World Wide Web at www.national.com.

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