Linear unveils synchronous buck-boost white LED driver

Date Announced: 11 Mar 2005 Linear Technology Corporation announces the LTC3453, a synchronous buck-boost DC/DC converter optimized for driving high current white LEDs at up to 500mA from a single Li-Ion battery input. The regulator operates automatically in either a synchronous buck, synchronous boost, or buck-boost mode, depending on input voltage and LED maximum forward voltage. This is of particular importance in high current LED applications because the LED forward voltage can vary from 2.7V to 4.9V depending on current levels and LED tolerances. The LTC3453’s buck-boost topology can deliver 90% efficiency over the entire Li-Ion voltage range of 2.7V to 4.2V. Independent high and low current settings for flash and torch/video modes respectively can be easily programmed with dual current setting resistors and dual enable pins.Efficiency of 90% can be typically achieved over the range of a Li-Ion battery. LED current is programmable to one of four levels (including shutdown) with dual current setting resistors and dual enable pins. In shutdown, the supply current is only 6uA. The device protects itself under open or shorted LED conditions. A high constant operating frequency of 1MHz allows the use of a small external inductor. The LTC3453 is offered in a low profile (0.75mm), thermally enhanced 16-lead (4mm x 4mm) QFN package.The LTC3453EDD is available from stock in a QFN-16 package. Pricing starts at $2.10 each for 1,000-piece quantities.Summary of Features: LTC3453High Efficiency: 90% Over Entire Single-Cell Li-Ion Battery RangeWide VIN Range: 2.7V to 5.5VUp to 500mA Continuous Output CurrentConstant Frequency 1MHz OperationLow Shutdown Current: 6uAInternal Soft StartOpen/Shorted LED ProtectionOvertemperature ProtectionSmall Thermally Enhanced 16-Lead (4mm x 4mm) QFN Package

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