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National Semiconductor Releases Industry's Most Advanced Controller for Forward Active Clamp Reset Converters

100V LM5026 Current-mode PWM Controller Simplifies Loop Compensation with Current-control Feedback, Reduces Total Part Count

Oct 11, 2005

October 11, 2005 - National Semiconductor Corporation (NYSE: NSM) today expanded its family of single and dual forward active clamp pulse-width modulation (PWM) controllers with the introduction of the LM5026, an integrated, 100V forward active clamp reset PWM controller that utilizes current-mode control.  This controller is designed for high switching frequencies and provides improved efficiencies and power densities compared to conventional forward converters.  It is well-suited for communication system DC-DC and AC-DC power conversion, as well as industrial power systems, including single- and multi-output industrial power supplies.

The LM5026 provides an array of features and flexibility that reduces the complexity and cost of external parts.  It enables designers to implement power converters using the active clamp reset technique with peak current-mode control.  Active clamp reset is one of the most popular single-ended topologies for isolated DC-DC converters in distributed power architectures.  It supports operation at duty cycles above 50 percent to efficiently deliver fixed, regulated output from a widely varying input supply.

“The LM5026 is the most advanced, feature-rich controller for the forward active clamp reset topology available today.  With this addition to National’s active clamp controller family, engineers now have the flexibility to design with the single-channel, current-mode LM5026, the single-channel, voltage-mode LM5025 or the dual-channel LM5034, which controls two interleaved power stages,” said Paul Greenland, director of strategic marketing for National Semiconductor’s Power Management Group.  “Together, this versatile family of controllers meets all the control and drive requirements of a wide range of power supply applications, while enabling higher efficiencies and power densities.”

About the LM5026
The LM5026 is a fully integrated PWM control system that includes a high-frequency oscillator, current-mode PWM control circuitry and two power MOSFET drivers for reduced component count and quick implementation of efficient forward active clamp converters.  The integrated 3A main MOSFET driver and 1A clamp MOSFET driver improve system efficiency and speed, eliminating the need for external drivers. The programmable, line-voltage-dependent, maximum-duty-cycle clamp minimizes voltage stress, reducing power MOSFET cost.  In addition, the unique current-mode feedback of the LM5026 increases the effective bandwidth of conventional opto-couplers to simplify compensation and improve overall loop bandwidth and transient response.

The LM5026 features an integrated, wide-range input start-up regulator that operates between 13V and 100V, eliminating the need for external start-up regulator components.  User-programmable under-voltage lockout and soft-start circuitry provide customers with the flexibility to control power-on sequencing and minimize start-up surge currents, while the programmable restart circuit supports three modes of over-current fault protection. The LM5026 also includes oscillator synchronization circuitry that allows users to control electromagnetic interference by locking the PWM controller to an external master clock.

About National’s Power Management Products
National Semiconductor is the number one supplier of power management ICs with 14.1 percent market share, according to iSuppli’s 2005 voltage regulator/reference survey.  National’s power management revenue grew 37.3 percent in 2004 over the previous year, compared to 24 percent growth for the industry.  National's innovative power management products include best-in-class linear regulators; power monitoring, control and reference ICs; and switching converters, such as high-voltage ICs for DC-DC conversion, switched capacitor converters, lighting management ICs and inductive switching converters.  National also offers online tools that enable power designers to select the best power management chips for their applications.  National's Webench® design tool allows designers to choose a product, create and analyze a design, and then build custom prototypes that can be delivered within 24 hours.  More information about National’s power management products is available at http://power.national.com

Pricing and Availability
Available now in 16-lead LLP® and TSSOP packages, the LM5026 is priced at $1.10 in 1,000-unit quantities.  For more information about the LM5026, including how to order samples and evaluation boards, please visit http://www.national.com/pf/LM/LM5026.html
Note to Editors:  To view a high-resolution downloadable photo of this product, visit National's photo gallery.

About National Semiconductor
National Semiconductor, the industry's premier analog company, creates high-value analog devices and subsystems.  National's leading-edge products include power management circuits, display drivers, audio and operational amplifiers, communication interface products and data conversion solutions.  National's key analog markets include wireless handsets, displays and a variety of broad electronics markets, including medical, automotive, industrial, and test and measurement applications.  Headquartered in Santa Clara, California, National reported sales of $1.91 billion for fiscal 2005, which ended May 29, 2005.  Additional company and product information is available at www.national.com