LM27953| Datasheet

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LM27953 White LED Driver with Four LED Current Sinks and 3/2x Switched Capacitor Boost

November 2004

LM27953 White LED Driver with Four LED Current Sinks and 3/2x Switched Capacitor Boost
General Description
The LM27953 is a charge-pump-based white-LED driver that is ideal for mobile phone display backlighting. It is intended to drive 4 LEDs for a main phone display backlight. Regulated internal current sources deliver excellent current and brightness matching in all LEDs. The LED driver current sinks can be used to backlight a main phone display with up to 4 LEDs. The low-side current drivers accommodate common-anode-type LEDs. The current sinks can also drive standard two-terminal LEDs, and provide other general lighting functions (keypad lighting, fun lighting, etc). The brightness of the LEDs can be adjusted independently with an external resistor. The LM27953 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 LM27953 is available in National's chip-scale 18-bump micro SMD package.

Features
n Drives 4 Individual Common-Anode LEDs with up to 20mA each for a Main Display Backlight n Independent Resistor-Programmable Current Setting 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

20128001

2004 National Semiconductor Corporation

DS201280

www.national.com