Designed to deliver constant current to drive high current LEDs, the LT3744 synchronous step-down DC/DC converter has been released by Linear Technology. The device’s 3.3V to 36V input voltage range makes it suitable for a wide variety of applications, including industrial, DLP projection and architectural lighting.
The converter uses two external switching MOSFETs, delivering up to 20A (80W) of continuous LED current from a nominal 12V input. In pulsed LED applications, the LT3744 can deliver up to 40A of LED current or 160W from a 12V input. Delivering efficiencies as high as 95%, the converter can eliminate the need for external heat sinking.
The device’s peak current mode controller maintains ±3% LED current regulation over a wide voltage range from VEE to VIN. By allowing VEE to float to negative voltages, several LEDs can be driven from a single Li-Ion battery with a simple, single step-down output stage. Additionally, this enables a unique inverting step-down topology which allows a single common anode heat sink to be used for RGB LEDs. A frequency adjust pin allows the user to programme the frequency between 100kHz and 1MHz, optimising efficiency while minimising external component size. Combined with its 5x6mm QFN package, the LT3744 offers a very compact 80W LED driver solution.
The converter provides both PWM dimming and CTRL dimming, which offer 3,000:1 dimming capability for four LED current levels, suitable for colour mixing applications, such as those required in DLP projectors. Similarly, the device’s unique topology enables it to transition between two regulated LED currents in less than 2µs, enabling more accurate colour mixing in RGB applications. LED current accuracy of ±3% is maintained to offer the most accurate brightness of light emitted from the LED. Additional features include output voltage regulation and open-LED and shorted-LED protection, open-drain output fault flag, frequency synchronisation and thermal shutdown.
The LT3744 is available in 36-pin 5x6mm QFN package. Two temperature grades are available, with operation from -40 to 125°C (junction) for the extended and industrial grades. The 1,000-piece price starts at $4.55 each. All versions are available from stock.