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Industry’s Smallest 80 V Buck Regulator from National Semiconductor Provides Cost-effective, Non-isolated Bias Power Supply Design

Sep 5, 2003

September 5, 2003 - Consolidating its leadership in high-voltage power management circuits, National Semiconductor Corporation (NYSE: NSM) today announced the industry’s smallest high-voltage Buck bias switching regulator to satisfy housekeeping or bias power needs in next-generation communication, automotive, 48 V distributed and battery-powered systems.

“Our new solution will displace a more expensive, less efficient transformer coupled flyback regulator that is currently being used by many designers to produce bias power,” said Paul Greenland, marketing director of National Semiconductor’s power management group.  “National Semiconductor’s LM5007 effectively eliminates cost and increases efficiency, adopting a simple inductor filter and a couple of external components.  Customers will benefit because the LM5007 offers more than 90 percent efficiency at a fraction of the cost and space consumed by today’s isolated bias supply solutions.”

National’s LM5007 is a Buck bias regulator which steps down a high-voltage (up to 75 V) primary-side power supply and produces a low voltage (10 V typical) bias supply for secondary-side control devices.  Fully integrated with all functions needed for a high-voltage power supply, the device contains an 80 V N-Channel power MOSFET rated at 0.7 A peak that can be switched at high frequencies (up to 500 kHz), allowing the use of a small output filter to complete a highly efficient, cost-effective bias supply solution that sources up to 0.5 A continuous load current in minimal printed circuit board (PCB) space.  Offered in a tiny (4 mm x 4 mm) 8-pin LLP® chip-scale package and an MSOP-8 package, the LM5007 outperforms existing Buck regulator solutions on the market in terms of FET breakdown, integrated boost capacitor diode, soft-start and thermal protection.

High Level of Integration
The control scheme deployed in the LM5007 eliminates the need for loop compensation while offering a very fast transient response using an ON-time that is inversely proportional to the input line voltage (Vin).  This produces a relatively constant and easily filtered switching frequency.  An intelligent current limit is implemented with a forced OFF-time, which is inversely proportional to Vout, ensuring short circuit protection with minimal foldback.

Integrating a 0.7 A peak, 80 V power MOSFET, the LM5007 serves an array of telecommunication, automotive and industrial power supply applications.  It provides an inexpensive bias supply that is easily implemented with the addition of a small inductor filter, greatly reducing component count and PCB space.   Also integrated in the LM5007 is a high voltage start-up bias regulator that operates from 9 V to 75 V plus over-temperature shutdown and an intelligent current limit OFF-time timer.

Packaging, Pricing and Availability
Available today, the LM5007 is offered in either an MSOP-8 package or a small, thermally enhanced 8-pin LLP chip-scale package and is priced at $1.05 each in 1,000 units. 

About National Semiconductor
National Semiconductor is the premier analog company driving the information age. Combining real-world analog and state-of-the-art digital technology, the company is focused on analog-based semiconductor products, which include stand-alone devices and subsystems in the areas of power management, imaging, display drivers, audio, amplifiers and data conversion. The company targets key markets such as wireless, displays, PCs, networks and a broad range of portable applications. With headquarters in Santa Clara, California, National reported sales of $1.67 billion for its most recent fiscal year. Additional company and product information is available on the World Wide Web at www.national.com