LM3519

LM3519 High Frequency Boost White LED Driver with High-Speed PWM Brightness Control September 2005 LM3519 High Frequency Boost White LED Driver with High-Speed PWM Brightness Control General Description 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 SOT23 package. Features n n n n n n n n n Drives 2 to 4 LEDs at 20mA Up to 30kHz PWM Dimming Control Capability > 80% Peak Efficiency Up to 8MHz Switching Frequency Small External Components: 1µH - 3.3µH(typ.2.2µH) Inductor and 1µF Output Capacitor True Shutdown Isolation Over-Voltage Protection Wide Input Voltage Range: 2.7V to 5.5V Small Footprint SOT23-6 Package Applications n LCD, White LED Backlighting on Mobile Phones n Digital Still Cameras and PDAs n General Purpose LED Lighting in H...