UM1661 Datasheet | Union Semiconductor

High Efficiency Low Noise PFM Step-Up DC/DC Converter UM1661 SOT23-6 General Description The UM1661 PFM step-up DC/DC Converter drives white LEDs with a constant current to provide backlight in cell phones, PDAs, and other hand-held devices. It Features allowing series connection of the white LEDs so that the LED currents are identical for uniform brightness. An enable input can be pulsed repeatedly to adjust LEDs brightness. The fast 500k Hz to 2MHz operation frequency allows for smaller capacitor and inductor. Fault condition protection uses cycle-by-cycle current limiting to sense maximum inductor current and over-voltage protection. The 0.2V low reference voltage minimizes the power loss across the current sense resistor. The converter can operate from 2V to 6V, and capable of delivering maximum 200m A output current at 4-LEDs application with 3V input voltage. Quiescent current drawn from power source is as low as 120u A. All of these Features make UM1661 be suitable for...