LM2791 Datasheet, PDF (1/11 Pages) National Semiconductor (TI) – Current Regulated Switched Capacitor LED Driver with Analog Brightness Control

July 2002
LM2791
Current Regulated Switched Capacitor LED Driver with
Analog Brightness Control
General Description
The LM2791 is a CMOS charge-pump voltage doubler and
regulator that provides two regulated current sources. The
LM2791 is designed to drive two white (or blue) LEDs with
matched currents (within ± 0.3%) to produce balanced light
sources for display backlights. They accept an input voltage
range from 3V to 5.8V and maintain a constant current
determined by an external set resistor.
The LM2791 delivers up to 36mA of load current to accom-
modate two high forward voltage (typically white) LEDs. The
switching frequency is 450kHz (min.) to keep the conducted
noise spectrum away from sensitive frequencies within por-
table RF devices.
In the LM2791, brightness is controlled by applying a voltage
between GND and 3.0V to the BRGT pin. The LM2791 is
available in active high or low shutdown versions. The shut-
down pin reduces the operating current to 1µA (max.).
The LM2791 is available in a 10 pin leadless leadframe
(LLP) CSP package.
Features
n Output matching of ± 0.3%
n Drives up to two LED’s
n 3V to 5.8V Input Voltage
n Up to 36mA output current
n Soft start limits inrush current
n Analog brightness control
n Separate shutdown input
n Very small solution size - no inductor
n 0.7mA typical operating current
n 1µA (max.) shutdown current
n 450kHz switching frequency (min.)
n Linear regulation generates predictable noise spectrum
n LLP-10 package: 3mm X 3mm X 0.8mm
Applications
n White LED Display Backlights
n White LED Keypad Backlights
n 1-Cell Li-Ion battery-operated equipment including
PDAs, hand-held PCs, cellular phones
n Flat Panel Dispalys
Basic Application Circuit
© 2002 National Semiconductor Corporation DS200183
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