Linear Technology announces the introduction of the LT3497, a dual, full-featured, step-up DC/DC converter that drives up to 12 white LEDs from a Li-Ion battery input. Its high efficiency, fixed frequency operation ensures consistent LED brightness and low noise and maximizes battery life. With an on-chip Schottky diode, no external diodes are required, saving cost and space. True Color PWMTM dimming achieves a dimming range of up to 250:1 without any color change in the LED. The LT3497's two independent converters are capable of driving asymmetric LED strings with up to 6 series LEDs per input voltage from 2.5V to 10V. Its 3mm x 2mm DFN package and tiny external components make for a very compact solution for space-constrained handheld applications.
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The LT3497's 2.3MHz constant switching frequency allows designers to minimize solution footprint and switching noise. Its 2.5V to 10V input voltage range allows the device to be used in handheld applications powered by single or two-cell Li-Ion batteries and applications powered by 5V fixed inputs. High-side current sensing allows each LED string to be driven with a single wire. The LT3497 acts as a constant current source and is responsible for delivering the same current to each white LED, independent of the LED's forward voltage drop fluctuations (which vary with temperature, manufacturing tolerances, and aging). Uniform LED brightness is ensured. Although two independent boost regulators can drive asymmetric LED strings on the same chip, each LED string has independent dimming and shutdown control. Other features include internal soft start/inrush current limit and LED open circuit protection. The LT3497 combines high efficiency, versatility, low noise, and minimal solution footprint, making it ideal for a wide range of backlighting applications that require a lot of white LEDs.
The LT3497 is available from stock in a 3mm x 2mm DFN-10 package. Buy in 1,000-piece quantities starting at $1.70 each.
Performance summary:
• Drive up to 12 white LEDs with 3V power supply (6 LEDs in series for each converter)
Two independent boost converters capable of driving asymmetric LED strings
Independent dimming and shutdown control of two LED strings
High-voltage side detection allows "one-wire current source" for each converter
? Internal Schottky diode
? LED open circuit protection (32V)
? 2.3MHz switching frequency
? ±5% benchmark accuracy
? VIN range: 2.5V to 10V
Both converters have a wide 250:1 True Color PWM dimming range
? Only 1μF output capacitor per converter
? 3mm x 2mm 10-pin DFN package
