National Semi Intros LM2639 Multi-Phase PWM Controller

National Semiconductor Corp. (Santa Clara, CA) announced the LM2639, a multi-phase pulse width modulation (PWM) controller claimed to provide the smallest power supply solution available for high-end desktop computers, workstations and servers using high-performance microprocessors such as Cyrix MII, Pentium II, Pentium III, Merced and K7. The LM2639 offers a power supply solution that enables a 70 percent reduction in board-required volume compared to a conventional single-phase dc/dc converter, according to National. The LM2639 meets the 20A/microsecond load transient demands of next generator processors. For loads greater than 40A for the next generation of high end processors such as K7 and Merced, the multiphase topology of the LM2639 is claimed to offer the smallest and most cost effective power supply solution. 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 reduced output capacitor bank. The LM2639 eliminates the need for large, 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. The controller is priced at $2.50 in quantities of 1,000.

National Semiconductor Corp.
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