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White LED driver integrates two LDOs

Milpitas, Calif. — Linear Technology Corp. has introduced 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. Housed in a 3 x 3-mm QFN package, the LTC3230 drives up to five 25 mA LED current sources, providing 125 mA of total output current, and integrates two 200 mA LDOs with separate enable and pin-selectable output voltages as low as 1.2 V and 1.8 V, respectively.

The 2.7-V to 5.5-V input voltage range has been optimized for single cell Li-ion/polymer applications. Efficiencies when driven from a Li-ion battery (3.6 V nominal) reach 91% with a quiescent current of 400 μA, which maximizes battery run-time. The LTC3230 requires only six small capacitors and one resistor to create a compact and low-profile (<9 mm2 package area, 0.75-mm high) solution.

The LTC3230's 900 kHz, 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, said Linear. 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. 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 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. The device also offers thermal limit and open/short LED protection.

Pricing: Starts at $1.55 each in quantities of 1,000.
Availability: The LTC3230EUD#PBF is available from stock in a 20-lead QFN (3 x 3mm) package.

Product information: LTC3230

Linear Technology Corp. , 1-408-432-1900, www.linear.com

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