Synchronous step-down LED driver
03 November 2009
Linear Technology’s LT3743 is a synchronous step-down DC/DC converter.
It has been designed to deliver constant current to drive high current LEDs. The device’s 5.5V to 36V input voltage range makes it ideal for a wide variety of applications, including industrial, DLP projection and architectural lighting.
The LT3743 provides up to 20A of continuous LED current from a nominal 12V input, delivering in excess of 80Watts. In pulsed LED applications, it can deliver up to 40A of LED current or 160Watts from a 12V input. Efficiencies as high as 95% eliminate any need for external heat sinking and significantly simplify the thermal design.
A frequency adjust pin enables the user to program the frequency between 100kHz and 1MHz so designers can optimise efficiency while minimising external component size. Combined with a 4mm x 5mm QFN or thermally enhanced TSSOP-28 package, the LT3743 offers a very compact high-power LED driver solution.
LT3743 offers both PWM and CTRL_SELECT dimming, offering 3,000:1 dimming capability at three LED current levels, making it ideal for colour mixing applications such as those required in DLP projectors. Similarly, the LT3743’s topology enables it to transition between two regulated LED current levels in less than 2µsec, enabling more accurate colour mixing in RGB applications. LED current accuracy of ±6% is maintained in order to ensure the most accurate luminosity of light from the LED. Additional features include output voltage regulation, open-LED protection, overcurrent protection and a thermal derating circuit.
The LT3743EUFD is available in a 28-pin 4mm x 5mm QFN package, whereas the LT3743EFE is available in a thermally enhanced TSSOP-28. Extended temperature versions, or ‘I’ grades, namely the LT3743IUFD and LT3743IFE are also available.
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