Synchronous step-down LED driver delivers up to 40A for high-current LEDs

27-03-2015 | Linear Technology | Power

Linear Technology has unveiled the LT3744, a new synchronous step-down DC-DC converter designed to deliver constant current to drive high current LEDs. The device's 3.3V to 36V input voltage range makes it ideal for a wide variety of applications, including industrial, DLP projection and architectural lighting. The LT3744 uses two external switching MOSFETs, delivering up to 20A (80W) of continuous LED current from a nominal 12V input. In pulsed LED applications, it can deliver up to 40A of LED current or 160W from a 12V input. Delivering efficiencies as high as 95%, it can eliminate the need for external heat sinking. The LT3744’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 program the frequency between 100kHz and 1MHz, optimizing efficiency while minimizing external component size. Combined with its 5mm x 6mm QFN package, the LT3744 offers a particularly compact 80W LED driver solution. The LT3744 provides both PWM dimming and CTRL dimming, which offer 3,000:1 dimming capability for four LED current levels, ideal for colour mixing applications, such as those required in DLP projectors. Similarly, its unique topology enables it to transition between two regulated LED currents in less than 2µsec, 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 synchronization and thermal shutdown. The LT3744 is available in 36-pin 5mm x 6mm QFN package. Two temperature grades are available, with operation from -40C to 125C (junction) for the extended and industrial grades., says the company.
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By Craig Dyball