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Updated: July 8th, 2008 05:26 PM CDT

National Semiconductor's Three New Inductor-less White LED Drivers Feature Dual-gain Architecture for Highest Efficiency in Portable Devices

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SANTA CLARA, Calif., March 27 /PRNewswire-FirstCall/ -- National Semiconductor Corporation (NYSE: NSM), the worldwide leader in power management technology, today introduced three new inductor-less white LED drivers for display backlighting in mobile phones, PDAs, portable gaming devices and MP3 media players. Using no external inductors, the LM27951, LM27952 and LM27964 significantly reduce the size of LED lighting solutions, while providing highly efficient switched-capacitor technology to extend battery life in portable devices.

These white LED drivers feature a dual-gain architecture that enables there gulators to automatically select between one of two gains from input voltage to output voltage, maximizing the efficiency of the regulator. The selectionis based on the input voltage of the regulator and the forward voltage of the LED.

"The dual-gain architecture of these new products provides excellent efficiency and extends the battery life of portable devices," said Mark Davidson , marketing director for National Semiconductor's Power Management Division. "The exceptional current matching is ideal for uniform lighting in thin handheld devices."

For uniform brightness across the display, the white led drivers offer current matching at just one percent between each LED. The LM27951, LM27952 and LM27964 are adaptive 1.5X/1X switched-capacitor current drivers that include pulse-width modulation (PWM) brightness control. The LM27964 also includes an I2C compatible interface to easily control the brightness of the LEDs, for a total output current of 180 mA.

Key Technical Specifications of National's LM27951 and LM27952 White LEDDrivers

The LM27951 and LM27952 charge-pump-based drivers are capable of driving up to four LEDs with 30 mA through each LED. Four tightly regulated current sources ensure excellent matching of LED drive current and LED brightness. The LED drive current value is programmed by an external resistor. The drivers operate over an input voltage range of 3.0V to 5.5V and require just four low-cost ceramic capacitors.

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