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National Semiconductor Introduces Step-Up Converter for White LED Applications

Dec 14, 2004

December 15 - National Semiconductor today introduced the LM3557, a fixed-frequency current-mode step-up DC-DC converter, suitable for white-LED applications. A cost-effective external feedback resistor is used to set a constant current through the LEDs. The LM3557 can drive up to five LEDs in series with 20 milliamps (mA) current and has a fixed 24V overvoltage protection option, eliminating the need for an extra protection diode. Applications for the LM3557 include color display backlighting, cellular phones and personal digital assistants (PDAs).

Key Features for LM3557:

  • VIN range: 2.7V-7.5V 
  • Small external components 
  • 1.25 MHz constant-switching frequency 
  • Output overvoltage protection 
  • Input undervoltage protection 
  • Cycle-by-cycle current limit 
  • True shutdown: No DC current paths to ground during shutdown 
  • Low profile LLP® package: <1 mm height - 8 pin 
  • No external compensation

Packaging, Pricing and Availability
National’s LM3557 is available now in an 8-lead LLP package and costs 96 cents in 1,000-unit quantities. 

About National Semiconductor
National Semiconductor, the industry's premier analog company, creates high- performance 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 markets include wireless handsets, displays, PCs and laptops.  The company's analog products are also optimized for numerous applications in a variety of electronics markets, including medical, automotive, industrial, and test and measurement.  Headquartered in Santa Clara, California, National reported sales of $1.98 billion for fiscal 2004, which ended May 30, 2004.  Additional company and product information is available at www.national.com
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