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National Semiconductor Introduces Integrated White LED Driver with Organic LED Display Power Supply

Nov 30, 2005

November 30, 2005 - National Semiconductor Corporation (NYSE:NSM) today introduced a small dual step-up DC-DC converter that drives up to five white LEDs with a constant current or an organic LED display with a constant voltage.  The LM3520 is well-suited for handheld devices such as flip and clam-shell cellular phones and digital cameras.

The LM3520 step-up converter uses pulse width modulation (PWM) mode to drive the LEDs and pulse frequency modulation (PFM) mode to drive the organic LED display.  This allows the best performance combination of high efficiency and stability.  When driving the LEDs, a single external resistor is used to set the maximum LED current.  The actual LED current and the brightness can be adjusted by applying a PWM signal to the enable pin.  When the LED drive is disabled, the LED string is disconnected on the low side so that there is no leakage current through the LEDs.

Key features for the LM3520 include:

  • Higher than 80 percent peak efficiency     
  • Drives up to 5 LEDs at 20 mA/3.6V and 4 LEDs at 30 mA/3.6V for the main display     
  • Up to 20V @ 50 mA/3.6V for the sub-display     
  • True shutdown isolation     
  • Small external components     
  • 1 MHz switching frequency     
  • 23V of over-voltage protection     
  • Wide input voltage range of 2.7V to 5.5V     
  • Cycle-by-cycle current limit     
  • PWM dimming control

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 LM3520 is available now in a small, low-profile 14-pin LLP® package that measures 3 mm x 4 mm x 0.8 mm and costs $2.60 in quantities of 1,000.  Lead-free package options are also available.

For more information about the LM3520 or to order samples, visit http://www.national.com/pf/LM/LM3520.html.  For more information on National’s white LED driver products, visit power.national.com.  A large selection of white LED drivers is supported by National’s WEBENCH online design tool.  To explore these solutions visit webench.national.com.  To learn more about designing with white LED drivers, visit National’s library of online seminars at http://www.national.com/onlineseminar/.

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