LT3744 High Current Synchronous Step-Down LED Driver Fea T Descrip T n Ideal for Driving Up to 40A LEDs The LT 3744 is a fixed frequency synchronous step-down n Up to 3000:1 PWM Dimming DC/DC controller designed to drive a LED load at up to 20A n 20:1 Analog Dimming continuous or 40A pulsed. The peak current mode controller n 3% Current Regulation Accuracy will maintain 3% LED current regulation over a wide output n 3% Voltage Regulation Accuracy voltage range, from VEE to V . By allowing VEE to float IN n Unique Inverting Buck-Boost Topology Allows to negative voltages, several LEDs in series can be driven Grounded Heat Sink to Be Used for RGB LEDs from a single Li-Ion battery with a simple, single step-down n 3.3V to 36V Input Voltage Range output stage. PWM dimming is achieved with the PWM pins. n Peak Current Mode with DC LED Current Sensing The regulated LED current is set with analog voltages at the n Open and Shorted LED Protection and Fault Reporting CTRL pins. Regulated voltage and overvoltage protection n Floating LED Driver Allows Single Power Solution are set with a voltage divider from the output to the FB pin. to Drive Multicolor LEDs or Single LED with Three The switching frequency is programmable from 100kHz to Different Regulated Currents 1MHz through an external resistor on the RT pin. n Thermally Enhanced 5mm 6mm QFN 36-Lead Additional features include an accurate external reference Package voltage, a control input for thermally derating regulation current, an accurate EN/UVLO pin, an open-drain output a T fault flag, OVLO, frequency synchronization, and thermal n LED Driver for DLP Projectors shutdown. n Heads-Up Displays L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. n High Power LED Protected by U.S. Patents, including 7199560, 7321203, 8120335 and 8901904. Typical a T LED Driver for DLP Projectors LED Current Waveforms (2000:1) 0A to 6.7A to 13.3A to 20A V IN EN/UVLO EN/UVLO V IN 3.3V TO 12V PWM1 20F 220F PWM2 PWM1 VEE PWM3 5V/DIV TG 220nF CTRL1 PWM2 CTRL2 BOOST 5V/DIV CTRL3 SW PWM3 LT3744 0.47H 1m 20A MAXIMUM 5V/DIV 2V V INTV REF CC 2.2F 22F 330F 100k 330F I LED BG 45.3k FAULT 330F 6.7A/DIV CTRLT VEE 51k ISP SGND 680k GREEN ISN 10F SYNC PWM OUT1 SS 3744 TA01b 25sec/DIV RT 1nF PWM OUT2 82.5k V FNEG VEE PWM OUT3 4.7nF 51k V LED ISP C1 4.7nF LED ISN 51k 3m FB V C2 4.7nF 10k 51k V C3 3744 TA01a VEE 3744fa 1 For more information www.linear.com/LT3744 ion pplica ions pplica ion uresLT3744 a T e Maxi Mu M r a T (Note 1) Relative to VEE (Tested with VEE = 0V and SGND = 20V): Relative to SGND (Tested with VEE = 0V and SGND = 0V): V ........................................................................36V V ........................................................................36V IN IN EN/UVLO ..............................................................36V EN/UVLO ..............................................................36V CTRL1, CTRL2, CTRL3 ..........................................23V CTRL1, CTRL2, CTRL3 ............................................3V CTRLT ...................................................................23V CTRLT ....................................................................3V ISP, ISN .................................................................36V ISP, ISN .................................................................36V LED ISP, LED ISN ..................................................3V LED ISP, LED ISN ..................................................3V V , V , V ...........................................................3V V , V , V ...........................................................3V C1 C2 C3 C1 C2 C3 V .........................................................15V to 3V V ..........................................................15V to 3V FNEG FNEG BOOST .................................................................. 41V BOOST .................................................................. 41V FAULT, SYNC .........................................................23V FAULT, SYNC ...........................................................3V PWM1, PWM2, PWM3 .........................................25V PWM1, PWM2, PWM3 ............................................5V FB ...........................................................................3V FB ...........................................................................3V SW ........................................................................36V SW ........................................................................36V INTV , RT, BG, TG, PWM OUT1, PWM OUT2, Storage Temperature Range ................ 65C to 150C CC PWM OUT3, V , SS ......................................Note 4 REF p c F T TOP VIEW 36 35 34 33 32 31 30 29 EN/UVLO 1 28 VEE CTRL1 PWM OUT1 2 27 V 3 26 VEE REF CTRL2 4 25 PWM OUT2 CTRL3 5 24 V FNEG 37 VEE CTRLT 6 23 PWM OUT3 PWM1 ISP 7 22 PWM2 8 21 ISN PWM3 9 20 V C1 SYNC 10 19 V C2 11 12 13 14 15 16 17 18 UHE PACKAGE 36-LEAD (5mm 6mm) PLASTIC QFN = 34C/W, = 3C/W JA JC EXPOSED PAD (PIN 37) IS VEE, MUST BE SOLDERED TO PCB 3744fa 2 For more information www.linear.com/LT3744 FAULT V IN SGND VEE RT INTV CC SS VEE LED ISN BG LED ISP BOOST FB SW V TG C3 ion igura on in ings bsolu