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 thermally-enchanced LLP package.