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ADM8843

Four White LED Backlight Driver

Analog Devices 

Data Sheet

Four White LED Backlight Driver

ADM8843

FEATURES

GENERAL DESCRIPTION

Drives 4 LEDs from a 2.6 V to 5.5 V (Li-Ion) input supply

1×/1.5×/2× fractional charge pump to maximize

power efficiency

0.3% typical LED current matching

Up to 88% power efficiency over Li-Ion range

Powers main and sub display LEDs with individual shutdown

Package footprint only 9 mm2 (3 mm × 3 mm)

Package height only 0.75 mm

Low power shutdown mode

Shutdown function

Soft start limiting in-rush current

APPLICATIONS

The ADM8843 uses charge pump technology to provide the

power to drive up to four LEDs. The LEDs are used for back-

lighting a color LCD display that has regulated constant current

for uniform brightness intensity. The main display can use up to

three LEDs, and the sub display uses one LED. The CTRL1 and

CTRL2 digital input control pins control the shutdown opera-

tion and the brightness of the main and sub displays.

To maximize power efficiency, the charge pump can operate in

1×, 1.5×, or 2× mode. The charge pump automatically switches

among 1×/1.5×/2× modes, based on the input voltage, to

maintain sufficient drive for the LED anodes at the highest

power efficiency.

Cellular phones with main and sub displays

White LED backlighting

Camera flash/strobes and movie light applications

Micro TFT color displays

DSC

PDAs

Improved brightness matching of the LEDs is achieved by a

feedback pin that senses individual LED current with a typical

matching accuracy of 0.3%.

FUNCTIONAL BLOCK DIAGRAM

C1

C2

1µF 1µF

VCC ADM8843

C4

4.7µF

CHARGE PUMP

1×/1.5×/2× MODE

CTRL1

CTRL2

CONTROL

LOGIC

OSC

VREF

VOUT

C3

2.2µF

MAIN

SUB

FB1

FB2

FB3

FB4

ISET

RSET

LED

CURRENT

CONTROL

CIRCUIT

CURRENT CONTROLLED SINKS

GND

Figure 1.

Rev. E

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