LT3743 High Current Synchronous Step-Down LED Driver with Three-State Control FEATURES DESCRIPTION n PWM Dimming Provides Up to 3000:1 Dimming Ratio The LT 3743 is a fixed frequency synchronous step-down n CTRL SEL Dimming Provides Up to 3000:1 Dimming DC/DC controller designed to drive high current LEDs. The Ratio Between Any Current average current mode controller will maintain inductor n Three-State Current Control for Color Mixing current regulation over a wide output voltage range of 0V n 6% Current Regulation Accuracy to (V 2V). LED dimming is achieved through analog IN n 6V to 36V Input Voltage Range dimming on the CTRL L, CTRL H and CTRL T pins and n Average Current Mode Control with PWM dimming on the PWM and CTRL SEL pins. n 2s Maximum Recovery Time Between Any Current Through the use of externally switched load capacitors, Regulation State the LT3743 is capable of changing regulated LED current n <1A Shutdown Current levels within several s, providing accurate, high speed n Output Voltage Regulation and Open-LED Protection PWM dimming between two current levels. The switching n Thermally Enhanced 4mm 5mm QFN and frequency is programmable from 200kHz to 1MHz through 28-Pin FE Package an external resistor on the RT pin. Additional features include voltage regulation and overvolt- age protection set with a voltage divider from the output APPLICATIONS to the FB pin. Overcurrent protection is provided and set n DLP Projectors by the CTRL H pin. n High Power Architectural Lighting L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and n True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are the Laser Diodes property of their respective owners. Protected by U.S. Patents including 7199560, 7321203, 8120335 and 8901904. TYPICAL APPLICATION 92% Efficient 20A LED Driver V IN EN/UVLO EN/UVLO V IN 10V TO 30V 4.7F PWM PWM 1F 4 CTRL SEL CTRL SEL M1 RT HG CTRL SEL 220nF SYNC 82.5k 5V/DIV OUTPUT CBOOT 1.1H 2.5m 20A MAXIMUM PWM V SW LT3743 REF 5V/DIV 2.2nF 4.7F 100k CTRL L V 330F CC INT SW 22F 3 20V/DIV R M2 HOT LG 100k CTRL H 499 330F GND 3 M3 + CTRL T SENSE I LED SENSE 10A/DIV R NTC PWMGH M4 10k SS PWMGL 10nF 3743 TA01b V = 24V 20s/DIV 51.1k IN 0A TO 2A TO 20A LED CURRENT STEP FB 330F V V 10.0k CL CH 3743 TA01a 3 34k 34k M1, M2: SiR462DP 8.2nF 8.2nF M3, M4: Si7234DP 3743fe 1 For more information www.linear.com/LT3743LT3743 ABSOLUTE MAXIMUM RATINGS (Note 1) V Voltage ................................................................40V CBOOT ......................................................................46V IN EN/UVLO Voltage ........................................................6V RT Voltage ..................................................................3V V Voltage ...............................................................3V FB Voltage ...................................................................3V REF CTRL L, CTRL H, CTRL T Voltage ............................3V SS Voltage ..................................................................6V PWM, CTRL SEL Voltage ...........................................6V SYNC Voltage ..............................................................6V + SENSE Voltage ........................................................40V Storage Temperature Range .................. 65C to 150C SENSE Voltage ........................................................40V Lead Temperature (Soldering, 10 sec) V , V Voltage .........................................................3V TSSOP ..............................................................300C CH CL SW Voltage ...............................................................40V PIN CONFIGURATION TOP VIEW TOP VIEW LG 1 28 V CC INT GND 2 27 GND CBOOT 3 26 V IN 28 27 26 25 24 23 SW 4 25 EN/UVLO GND 1 22 PWMGL HG 5 24 V EN/UVLO 2 21 GND REF PWMGL 6 23 V 3 20 GND CTRL T REF GND CTRL T 4 19 PWMGH 7 22 GND 29 29 GND GND GND 5 18 PWMGH PWM 8 21 CTRL H CTRL H 6 17 CTRL SEL PWM 9 20 CTRL L CTRL L 7 16 SYNC CTRL SEL 10 19 SS SS 8 15 RT SYNC 11 18 GND 9 10 11 12 13 14 RT 12 17 FB + V 13 16 CH SENSE V 14 15 CL SENSE UFD PACKAGE 28-LEAD (4mm 5mm) PLASTIC QFN FE PACKAGE 28-LEAD PLASTIC TSSOP T = 125C, = 37C/W JMAX JA EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB T = 125C, = 30C/W JMAX JA EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION (Note 2) LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3743EUFD PBF LT3743EUFD TRPBF 3743 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3743IUFD PBF LT3743IUFD TRPBF 3743 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3743EFE PBF LT3743EFE TRPBF LT3743FE 28-Lead Plastic TSSOP 40C to 125C LT3743IFE PBF LT3743IFE TRPBF LT3743FE 28-Lead Plastic TSSOP 40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: