The SC621 from Semtech is a Charge Pump LED Driver IC that has been optimized for use in single-cell Li-ion battery applications. It requires an input voltage of 3 – 5.5 V and provides an output voltage of 2.5-5.25 V. This LED driver consists of a multi-mode fractional charge pump, four LEDs, a 400-mA flash LED, two LDOs, SemWire digital interface and logic control, an oscillator, a current setting DAC, a voltage setting DAC, flash control, and a battery. This charge pump provides backlight current in conjunction with four matched current sinks and supplies either continuous or burst-type current to a flash LED using the dedicated flash driver current sink. It includes an optional fade-in/fade-out function that gradually adjusts the backlight current, thereby simplifying the control software. This LED driver IC also offers a flash time-out feature to disable the flash if it remains active for more than a second. It uses the two low-dropout, low-noise linear voltage regulators for powering a camera module or other peripheral circuits.
This WEEE-compliant LED driver uses the proprietary SemWire single-wire interface technology to control all functions, including the backlight, flash current, and the output of two LDOs. It reduces quiescent current to 100 μA while continuing to monitor the serial interface, which results in better power efficiency. This RoHS-compliant IC is available in a surface-mount package that measures 3 x 3 x 0.6 mm and is ideal for cellular phone backlighting and flash, PDA backlighting and flash, camera I/O, and core power applications.