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NSC PWM controller meets IBA specs

Posted: 02 Jun 2004 ?? ?Print Version ?Bookmark and Share

Keywords:national semiconductor? nsc? lm5033? pwm controller? intermediate bus architecture?

The Intermediate Bus Architecture (IBA) consists of an isolated bus converter powered from a higher-voltage distributed power rail that produces an "intermediate" lower voltage distribution bus, typically 8V to 14V, to feed multiple nonisolated regulators at the point of load. Since the IBA uses two stages of power conversion, the bus converter and point-of-load regulators must be more efficient and fit in a smaller board area to offer a compelling alternative to single-stage distributed power systems.

To address these challenges, National Semiconductor Corp. (NSC) designed the LM5033 PWM controller with the flexibility to be used standalone in a push-pull bus converter or paired with one or two of the company's LM5100 drivers in a half- or full-bridge converter design. According to NSC, this flexibility allows designers to produce a family of bus converters that deliver a wide range of output power levels for telecom and computing power systems.

The LM5033 is also claimed by the company as the industry's first fully featured 100V dc-dc PWM controller that meets the challenging specifications of the IBA.

The recently introduced architecture controls the multiple low-voltage power supply rails in complex power systems using digital ASICs, DSPs and FPGAs that are found in telecommunications, automotive and industrial applications.

"The introduction of the Intermediate Bus is an inflection point in the evolution of distributed power architectures," said Paul Greenland, marketing director for NSC's Power Management group. "Customers expect the next-generation of intermediate bus converters to be flexible and efficient without sacrificing real estate."

Includes internal start-up regulator

Designed on the company's new Analog-BiCMOS-DMOS high-voltage process technology, the LM5033 operates off a wide range of input voltages from 15V to 100V for lower component count and higher efficiency. It also has efficient PWM and gate driver performance at frequencies up to 1MHz.

With an internal high-voltage start-up regulator, the voltage-mode PWM controller features a <100ns propagation delay on current limit that permits smaller margins in the power train components, 1.5A MOSFET drivers that are capable of driving larger MOSFETs for higher power throughput, a switching frequency that can be set by a single resistor, a direct opto-coupler interface, a soft start that reduces in-rush current, and an under-voltage lock-out with hysteresis that prevents malfunctions during start-up or brown-outs.

Offered in a 10-lead LLP package with a 4-by-4mm footprint (38C per W), the LM5033 is priced at $1.10 each, while the LM5100 is available in an SOIC or LLP package for $1.35 each, both in 1,000-unit volumes.

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