Offering the best mix of performance, price and functionality, National Semiconductor Corporation announced two highly integrated power management controllers for today's complex embedded computer applications. These products offer a complete power supply for any microprocessor, FPGA or DSP-based system in one compact device. National's new high-efficiency synchronous step-down regulator controllers have multiple outputs that can power notebook computers, networking equipment, internet appliances, set-top boxes, graphics cards including DDR memory, and industrial computer boards.

The LM2633 and LM2645 combine all the blocks needed to create a PCB-level power supply that can operate over an input range of 4.5V to 30V with maximum efficiency. With their wide input voltage range, 10µA shutdown current, and superior performance, these controllers meet the needs of portable and line-powered systems.

"Multiple IC process technologies dictate more and varied power sources in computer-based system design," said John Perzow, National's business marketing manager for power management products. "National is the only company that combines this level of functionality and performance into one competitively-priced package."

The LM2633 is a highly complex part full of features, but the most important is that National has managed to design the input so that the analog self-start for the switching controllers is independent of the input voltage's slew rate. With so much else happening this will make the designer's work a lot easier by being able to accurately predict behavior under different input circumstances.

The two controllers have different characteristics although most of the channel architecture is the same: The first controller provides Intel-compatible performance with an output programmed  by a 5-bit DAC between 0.925 and 2.00 V. The second controller is adjustable from 1.25 to 6.0 V. Efficiencies are high and the input voltage can range from 4.5 to 30 V and the switching frequency is at 250 kHz for inputs less than 17 V; a skip operation is available with a cycle-by-cycle current limit. The part also provides a 5-V source for external boot-strap circuits if another supply is not available. A power good signal indicates the general behavior of the supplies. The drain-source voltage of the upper FET is used for current-mode control so that no external sense resistor is required.

The two controllers normally operate out of phase -- which reduces the input ripple and makes the input filter less complex to design -- but they can also be operated in parallel to lower system noise and increase power density. The linear section of the part offers an adjustable output voltage with a 50 mA maximum driving current. The additional linear regulator on the LM2645 is a 3.3 V, 50 mA feature.