- Drives 4 Series White LEDs with up to 30mA
- >80% Peak Efficiency
- Up to 100kHz PWM Brightness Control
Texas Instruments LM3508TLEV
The LM3508 is a synchronous boost converter (no external Schottky diode required) that provides a constant current output. It is designed to drive up to 4 series white LEDs at 30mA from a single-cell Li-Ion battery. A single low power external resistor is used to set the maximum LED current. The LED current can be adjusted by applying a PWM signal of up to 100kHz to the DIM pin. Internal soft-start circuitry is designed to eliminate high in-rush current at start-up. For maximum safety, the device features an advanced short-circuit protection when the output is shorted to ground. Additionally, over-voltage protection and an 850 kHz switching frequency allow for the use of small, low-cost output capacitors with lower voltage ratings. During shutdown, the output is disconnected from the input preventing a leakage current path through the LEDs to ground.
The LM3508 is a synchronous step-up Dc/Dc converter deisgned for white LED applications. The evaluation board is set up to drive 4 standard VF white LEDs from a 2.7V to 5.5V input supply. The application note contains information about the evaluation board.