The LM3519 drives up to 4 white LEDs with constant current to provide LCD backlighting in handheld devices. The LED current is internally set to 20mA. The series connection allows the LED current to be identical for uniform brightness and minimizes the number of traces to the LEDs. Brightness control is achieved by applying a PWM signal on enable with frequencies up to 30kHz. The LM3519 features a proprietary PFM regulation architecture with switching frequencies between 2MHz to 8MHz, minimizing inductor size. Over-voltage protection circuitry and high frequency operation permit the use of low-cost small output capacitors. During shutdown, the output is disconnected from the input in order to avoid leakage current path through the LEDs to ground. The LM3519 is available in a tiny 6-pin SOT-23 package.