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National Semiconductor Introduces Family of Constant Current LED Drivers Featuring PWM and Analog Brightness Control for Dual- and Large-format Displays

Nov 22, 2005

November 22, 2005 - National Semiconductor Corporation (NYSE:NSM) today introduced two additional members of a family of fixed-frequency, current-mode controlled step-up DC-DC converters with true shutdown isolation.  Available in a very small 10-bump micro SMD package or low-profile 16-pin LLP® package, the LM3502 and LM3503 provide a complete solution for driving dual-display or large, single white LED string backlighting applications.

In portable applications with large format or multiple displays, the LM3502 and LM3503 provide an output voltage of 40V that drives up to 10 white or blue LEDs in one or two series strings.  Either one or both of the strings can be independently enabled or shut off.  When shut down, the converters completely disconnect the input from the output, creating total isolation and preventing any leakage currents from trickling into the LEDs.  A single external resistor is used to set the maximum LED current in driver applications.  The LED brightness can be controlled by a PWM signal with the LM3502 and by an analog signal with the LM3503.

Key features for the LM3502 and LM3503 include:

  • Drive up to 4, 6, 8 or 10 white LEDs in dual display backlighting applications     
  • Two internal white LED current bypass FET switches     
  • Greater than 80 percent efficiency     
  • Output voltage options of 16V, 25V,  35V and 44V     
  • Internal soft-start, eliminating in-rush current     
  • 1 MHz constant-switching frequency     
  • Wide input voltage of 2.5V to 5.5V     
  • Small external components

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.

Packaging, Pricing and Availability
National’s LM3502 and LM3503 are available now.  In quantities of 1,000, the LM3502 and the LM3503 cost $2.11 in a very small 10-bump micro SMD package and $1.93 in the 16-pin LLP package.  Lead-free package options are also available.

For more information about the LM3502 or to order samples, visit http://www.national.com/pf/LM/LM3502.html.  For more information about the LM3503 or to order samples, visit http://www.national.com/pf/LM/LM3503.html.

For more information on National’s white LED driver products, visit power.national.com. National’s WEBENCH online design tool supports a large selection of white LED drivers.  To explore these solutions, visit http://webench.national.com.  To learn more about designing with white LED drivers, visit National’s library of online seminars.

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