Tiny DC/DC drives up to 12 white LEDs

Linear Technology Corp. has announced 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 device promises high-efficiency, fixed frequency operation to ensure uniform LED brightness, low noise and maximum battery life. Its on-chip Schottky diodes eliminate both the added cost and space of external diodes.

250:1 dimming
True Color PWMTM 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 2.5-10V. Its 3-by-2mm DFN package and tiny externals provide a very compact footprint for space-constrained handheld applications.

The LT3497's 2.3MHz constant switching frequency allows the designer to minimize both solution footprint and switching noise. Its 2.5-10V 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 lets each string of LEDs be driven by a single wire.

Uniform brightness
The LT3497 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 combination of the LT3497 is suitable for backlighting applications that require many white LEDs in a tiny form factor.

The LT3497 is available from stock in a 3-by-2mm DFN-10 package. Pricing starts at $1.70 for 1,000-piece quantities.