Linear Technology announces the LT3497, a dual, full- featured, step-up DC/DC Converter designed to drive up to 12 white LEDs from a Li-Ion input. The on-chip schottky diodes eliminate external diodes. True Color PWM dimming enables dimming ranges of up to 250:1 without any color shift of the LEDs. The LT3497's two independent converters are capable of driving asymmetric LED strings (up to 6 in series per converter) from an input voltage of 2.5V to 10V. The LT3497's 2.3MHz constant switching frequency enables the designer to minimize both solution footprint and switching noise. Its 2.5V to 10V input voltage range enables the device to operate in applications from single or dual cell Li-Ion powered handheld devices as well as 5V fixed inputs. Its high side current sense enables each string of LEDs to be driven by a single wire. The device acts as a constant current source, delivering the same current to each white LED, regardless of fluctuations in the LED's forward voltage drop which varies with temperature, manufacturing tolerances and age, ensuring uniform LED brightness. Although on the same chip, the independent step-up converters are capable of driving asymmetric LED strings, with independent dimming and shutdown control of each string. Additional features include internal soft-start/inrush current limiting, and open LED protection. The LT3497 is available from stock in a 3mm x 2mm DFN-10 package. Pricing starts at $1.70 for 1,000-piece quantities.
Features of the LT3497
Drives up to 12 white LEDs (6 in Series per Converter) from a 3V supply
Two independent Boost Converters
Capable of driving asymmetric LED strings
Independent dimming and shutdown control of the two LED strings
High side sense allows "One wire current source" per Converter
Internal Schottky diodes open LED protection (32V)
2.3MHz switching frequency
±5% Reference Accuracy VIN Range: 2.5V to 10V
Dual wide 250:1
True Color PWM dimming requires 1µF output capacitor per converter
