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LED driver with dual LDOs suits portable apps

Posted: 19 Sep 2007 ?? ?Print Version ?Bookmark and Share

Keywords:LED driver? dual LDO? portable application?

Linear Technology Corp. has introduced the LTC3230 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.

The device 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 percent with quiescent current of only 400?A, maximizing battery run-time. The LTC3230 also requires only six small capacitors and one resistor to create a tiny, low profile solution footprint.

In addition, the LTC3230's 900kHz, high efficiency multimode 1x/1.5x/2x 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 (1.5x) when any enabled LED current source approaches dropout. A subsequent dropout switches the part into 2x mode.

Also, 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 device 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 x 3mm) package. Pricing starts at $1.55 each for 1,000-piece quantities.




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