LM2796

Dual-Display White LED Driver with 3/2x Switched

Capacitor Boost

General Description

The LM2796 is a charge-pump based white-LED driver that

is ideal for mobile phone display backlighting. It can drive up

to 7 LEDs in parallel with up to 20mA through each LED.

Regulated internal current sources deliver excellent current

and brightness matching in all LEDs. The LED-driver current

sources are split into two independently controlled groups.

The primary group (4 LEDs) can be used to backlight the

main phone display. The second group (3 LEDs) can be

used to backlight a secondary display or to provide other

lighting features (keypad LEDs, for example). Brightness of

the two groups can be adjusted independently with pulse-

width modulated (PWM) digital signals.

The LM2796 works off an extended Li-Ion input voltage

range (2.7V to 5.5V). Voltage boost is achieved with a high-

efficiency 3/2x-gain charge pump.

The LM2796 is available in National’s chip-scale 18-bump

micro SMD package.

Features

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Drives up to 7 LEDs with up to 20mA each

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LEDs controlled in 2 Distinct Groups, for Backlighting 2

Displays (main LCD and sub-LCD)

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Excellent Current and Brightness Matching

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High-Efficiency 3/2x Charge Pump

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Extended Li-Ion Input: 2.7V to 5.5V

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PWM Brightness Control: 100Hz - 1kHz

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18-bump Thin Micro SMD Package:

(2.1mm x 2.4mm x 0.6mm)

Applications

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Mobile Phone Display Lighting

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Mobile Phone Keypad Lighting

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PDAs

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General LED Lighting

Typical Application Circuit

20093801

February 2004

© 2004 National Semiconductor Corporation

DS200938

www.national.com