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Main/Camera Cell Phone LED Driver Features 500mA Total Output Current & 95% Efficiency

Feb 7 2006 - MILPITAS, CA
  • Linear Technology Corporation announces the LTC3210, a highly integrated, 800kHz, low noise, high efficiency 1×/1.5×/2× multimode charge pump for driving Main and Camera LEDs in cellular phones. It provides 5 LED current sources at up to 500mA of total output current: a 4×25mA LED Main display, and one high-current 400mA Camera LED display, all from a compact 3mm × 3mm QFN package. Each display is digitally controlled with independent dimming and programming via a single wire interface. The LTC3210's input voltage range of 2.9V to 4.5V is optimized for single cell Li-Ion cellular applications. Efficiencies when driven from a Li-Ion battery (3.6V nominal) reach 95% with quiescent current of only 400uA, maximizing battery run-time. High switching frequency enables the use of small external capacitors. The LTC3210 requires only four small capacitors and two current set resistors to create a tiny, 20mm2, low profile (0.75mm) solution footprint.

    The LTC3210 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 1× 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 and CAM displays are set with two resistors, one per display. LED currents are controlled with precision internal current sources, while dimming and ON/OFF control for each display are achieved via a single-wire interface. The LTC3210 has 64 brightness levels for the Main display and 8 levels for the CAM output. Internal circuitry prevents inrush current and excessive input noise during start-up and mode switching; in addition the device has open/short LED protection.

    The LTC3210EUD is available from stock in a low profile (0.75mm) 16-lead QFN (3mm × 3mm) package. Pricing starts at $1.70 each for 1,000-piece quantities.

    Summary of Features: LTC3210

    • Up to 95% Efficiency without Inductors
    • Multimode, Automatic Switching 1×/1.5×/2× Charge Pump for Optimal Efficiency
    • Up to 500mA Total Output Current
    • 5 Current Sources Available for Main Display and Camera LED Drivers:
      • Four 25mA Low Dropout Main LED Outputs
      • One High-Current 400mA Low Dropout CAM LED Output
    • Individual Full-Scale Current Set Resistors
    • Single Wire Enable Brightness Control for Main and CAM LEDs
    • 64:1 Brightness Control Range for Main Display
    • Low Noise, Constant Frequency Operation
    • Internal Soft-Start Limits Inrush Current During Start-Up and Mode Switching
    • Open/Short LED Protection
    • 2.9V to 4.5V Input Voltage Range
    • 3mm × 3mm × 0.75mm QFN-16 Package
    LTC3210 PR Image

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