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Five-Output 25mA/LED Driver with Two LDOs Operates Down to 2.7V

Sep 12 2007 - MILPITAS, CA
  • Linear Technology Corporation announces the LTC3230, an integrated white LED driver with dual LDO regulators for driving Main and Sub LED displays and supplying low-voltage system rails in portable electronic devices, all in a compact 3mm × 3mm QFN package. The LTC3230 drives up to five 25mA LED current sources, providing 125mA of total output current, and integrates two 200mA LDOs with separate enables and pin-selectable output voltages as low as 1.2V and 1.8V, respectively. The LTC3230’s 2.7V to 5.5V input voltage range has been optimized for single cell Li-Ion/Polymer applications. Efficiencies when driven from a Li-Ion battery (3.6V nominal) reach 91% with quiescent current of only 400uA, maximizing battery run-time. The LTC3230 requires only six small capacitors and one resistor to create a tiny, low profile (2 package area, 0.75mm high) solution footprint.

    The LTC3230’s 900kHz, high efficiency multimode 1×/1.5×/2× charge pump features low-noise constant-frequency operation and automatically optimizes efficiency based on VIN and LED forward voltage conditions. The device powers up in 1x mode and automatically switches to boost mode (1.5×) when any enabled LED current source approaches dropout. A subsequent dropout switches the part into 2× mode. Maximum currents for the Main/Sub displays are set with a single resistor. LED currents are controlled with precision internal current sources and brightness, dimming and ON/OFF control for all displays are achieved via a simple single-wire interface. The LTC3230 provides 32 brightness levels for both the Main and Sub displays. Internal circuitry prevents inrush current and excessive input noise during start-up and mode switching. In addition, the device has thermal limit and open/short LED protection.

    The LTC3230EUD#PBF is available from stock in a 20-lead QFN (3mm × 3mm) package. Pricing starts at $1.55 each for 1,000-piece quantities.

    Summary of Features: LTC3230

    • Up to 91% Efficiency without Inductors
    • Multimode, Automatic Switching 1×/1.5×/2× Charge Pump
    • Up to 125mA Total Output Current
    • Five 25mA Current Sources Available as Main (4) and Sub (1) LED Drivers
    • LED ON/OFF, Brightness Level Configurable Using 1-Wire Interface
    • 32:1 Linear LED Brightness Control
    • Dual 200mA Linear Regulators with Pin-Selectable Output Voltages
    • Low Noise, Constant Frequency Operation
    • Internal Soft-Start Limits Inrush Current During Start-Up & Mode Switching
    • Thermal Limit/Open-Short LED Protection
    • 2.7V to 5.5V Input Voltage Range
    • 3mm × 3mm × 0.75mm QFN-20 Package

    Five-LED Main/Sub Display Driver + Dual LDO

    LTC3230 PR Image

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