LM3520 Datasheet, PDF (1/14 Pages) National Semiconductor (TI) – Integrated White LED Driver with Organic LED Display Power Supply

PRELIMINARY
February 2005
LM3520
Integrated White LED Driver with Organic LED Display
Power Supply
General Description
The LM3520 is a dual step-up DC/DC converter, designed to
drive up to 5 white LEDs with a constant current and to
power an organic LED display with a constant voltage.
A single external resistor is used to set the maximum LED
current. The LED current can be adjusted by applying a
PWM signal to the EN pin. For higher efficiency the LM3520
operates with pulse frequency modulation (PFM) control
scheme when the sub-display is enabled. When Main dis-
play is enabled, the device is operating in PWM mode.
Overvoltage protection circuitry and a 1MHz switching fre-
quency allow for the use of small, low cost external compo-
nents.
Additional features include a low-side NFET switch that can
turn off the LED string with no DC current path to ground.
The LM3520 is available in a small 14-pin thermally-
enchanced LLP package.
Features
n Integrated OLED and white-LED driver
n 80% efficiency
n Drives up 5 LEDs at 20mA/3.6V and 4 LEDs at
30mA/3.6V for main-display
n Up to 20V @ 50mA/3.6V for sub-display
n True shutdown isolation
n Small External Components
n 1 MHz Switching Frequency
n 23V OverVoltage Protection
n Wide Input Voltage Range: 2.7V to 5.5V
n Cycle-By-Cycle Current Limit
n PWM Dimming Control
n Low Profile 14-Pin LLP(3mm x 4mm x 0.8mm)
Applications
n Flip-phones/Clam-shell Cellular Phones
n Handheld Devices
n High-fashion cellular phones
n White LED Backlighting
n Digital Cameras
Typical Applications
Main Display with OLED Sub Display
© 2005 National Semiconductor Corporation DS201288
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