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National Semiconductor Introduces Miniature, High-Frequency White LED Driver with High-Speed PWM Brightness Control

Sep 22, 2005

September 22, 2005 - National Semiconductor Corporation (NYSE:NSM) today introduced a tiny high-frequency white LED driver that features high-speed pulse width modulation (PWM) brightness control for handheld devices.  The LM3519 drives up to four white LEDs with constant current for backlighting high-resolution displays in mobile phones, MP3 players, barcode scanners and other handheld portable devices.

The LM3519 is a highly efficient LED driver that delivers 20 mA to the LEDs with internal current regulation, eliminating the need for an external resistor. Brightness control is achieved by applying a PWM signal to the enable pin with frequencies up to 30 kHz to avoid audible noise.

The LM3519 features proprietary pulse frequency modulation regulation architecture with switching frequencies from 2 MHz to 8 MHz, minimizing inductor size.

Over-voltage protection circuitry and high-frequency operation allow the use of low-cost, small-output capacitors.  During shutdown, the output is disconnected from the input in order to avoid leakage current path through the LEDs to ground.

Key Features for LM3519:

  • Drives 2 to 4 LEDs at 20 mA
  • Greater than 80% Efficiency 
  • Up to 8 MHz Switching Frequency
  • Up to 30 kHz PWM Dimming Control 
  • Small External Components: 1 µH - 3.3 µH (typ. 2.2 µH) Inductor and 1 µF Output Capacitor 
  • True Shutdown Isolation 
  • Over-Voltage Protection 
  • Wide Input Voltage Range: 2.7V to 5.5V

Packaging, Pricing and Availability
Available now, the LM3519 is packaged in a tiny SOT23-6 and costs 70 cents in quantities of 1,000.  Lead-free package options are also available.  For more information on National’s switching regulators, visit power.national.com.  For more information on the LM3519 or to order samples, visit http://www.national.com/pf/LM/LM3519
.  A selection of switching regulators is supported by National’s WEBENCH® online design tool.  To explore these solutions, visit http://webench.national.com.

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