Monday, January 21, 2008

Linear Technology LTC3220/-1 LED driver

Linear Technology has announced the LTC3220/-1, an inductorless, low noise, high efficiency LED driver for cell phone displays and other programmable lighting applications.

The IC provides 18 individually configurable LED current sources for flexibility in programming multiple displays. The display currents are set via a precision internal current reference.

The universal current sources can be digitally controlled with independent dimming, brightness, blinking, and gradation control, programmable via a simple two-wire I2C serial interface; LTC3220 and LTC3220-1 each offer a unique I2C address.

The LTC3220/-1's 2.9V to 5.5V input voltage range has been optimised for single-cell Li-Ion/Polymer battery applications. Efficiencies when driven from a Lithium battery (3.6V nominal) reach 91%, with quiescent current as low as 500uA, maximizing battery run-time. Furthermore, slew-rate limited switching reduces conducted and radiated noise (EMI).

The LTC3220/-1's multimode charge pump features low-noise constant-frequency operation, automatically optimising efficiency based on the voltages across the LED current sources.

The device powers up in 1x mode and automatically switches to boost mode (1.5x) when any enabled LED current source approaches dropout; a subsequent dropout switches the device into doubler (2x) mode. Internal circuitry prevents inrush current and excessive input noise during start-up and mode switching. In addition, the device has short circuit and thermal protection.

The LTC3220/-1 is available from stock in the ultra-thin (0.55mm) 28-lead QFN (4mm x 4mm) package. The IC requires only five small capacitors for a tiny, complete LED power supply and current controller solution. Pricing starts at $2.35 each for 1,000-piece quantities.

Summary of Features: LTC3220/-1

  •  18x20mA Independently Configurable Universal Current Sources with 64-Step Linear Brightness Control
  •  Independent ON/OFF, Brightness Level, Blinking and Gradation Control for Each Current Source Using 2-Wire I2C Interface
  •  Multimode 1x/1.5x/2x Low Noise Charge Pump Provides up to 91% Efficiency
  •  Slew Rate Limited Switching Reduces Conducted & Radiated Noise (EMI)
  •  Up to 360mA Total Output Current
  •  2.9V to 5.5V Input Voltage Range Optimised for Li-Ion/Polymer Applications
  •  Internal Current Reference
  •  Single Reset Pin for Asynchronous Shutdown and Reset of All Data Registers
  •  Two I2C Addresses are Available (LTC3220: 0011100; LTC3220-1: 0011101)
  •  Automatic or Forced Mode Switching
  •  Internal Soft-Start Limits Inrush Current
  •  Short Circuit/Thermal Protection
  •  Ultrathin (0.55mm) 4mm x 4mm QFN-28 Package 


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