LM3520

LM3520 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 display is enabled, the device is operating in PWM mode. Overvoltage protection circuitry and a 1MHz switching frequency allow for the use of small, low cost external components. 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 thermallyenchanced 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 n n n n Flip-phones/Clam-shell Cellular Phone...