LM3519 Datasheet | National Semiconductor

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 20m A. 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 30k Hz. 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 20m A Up to 30k Hz PWM Dimming Control Capability > 80% Peak Efficiency Up to 8MHz Switching Frequency Small External ponents: 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 Handheld Devices Typical Application FIGURE 1. Typical Application Circuit © 2005 National Semiconductor Corporation DS201602 .national. Connection Diagram 6-Lead SOT23 Package Top View Pin Descriptions Pin # 1 2 3 4 5 6 Name En Gnd VOUT LED_rtn SW VIN Device Enable Connection Ground Connection Output Voltage Connection White LED Current Sensing Input Connection Drain Connection of the Internal Power Field Effect Transistor (FET) Switch Input or Supply Voltage Connection Description Ordering Information Current Option 20 m A Order Number LM3519MK-20 LM3519MKX-20 Package Marking D52B D52B 1000 Units, Tape-and-Reel 3000 Units, Tape-and-Reel Supplied...