LM2796| Datasheet

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LM2796 Dual-Display White LED Driver with 3/2x Switched Capacitor Boost

February 2004

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 pulsewidth 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 highefficiency 3/2x-gain charge pump. The LM2796 is available in National's chip-scale 18-bump micro SMD package.

Features
n Drives up to 7 LEDs with up to 20mA each n LEDs controlled in 2 Distinct Groups, for Backlighting 2 Displays (main LCD and sub-LCD) n Excellent Current and Brightness Matching n High-Efficiency 3/2x Charge Pump n Extended Li-Ion Input: 2.7V to 5.5V n PWM Brightness Control: 100Hz - 1kHz n 18-bump Thin Micro SMD Package: (2.1mm x 2.4mm x 0.6mm)

Applications
n n n n Mobile Phone Display Lighting Mobile Phone Keypad Lighting PDAs General LED Lighting

Typical Application Circuit

20093801

2004 National Semiconductor Corporation

DS200938

www.national.com