LT3956 80V , 80V IN OUT Constant-Current, Constant-Voltage Converter Fae Tseru Dpircse Tnoi TM n 3000:1 True Color PWM Dimming The LT 3956 is a DC/DC converter designed to operate as n Wide Input Voltage Range: 4.5V to 80V a constant-current source and constant-voltage regulator. n Output Voltage Up to 80V It is ideally suited for driving high current LEDs. It features n Internal 3.3A/84V Switch an internal low side N-channel power MOSFET rated for n Constant-Current and Constant-Voltage Regulation 84V at 3.3A and driven from an internal regulated 7.15V n supply. The fixed frequency, current-mode architecture 250mV High Side Current Sense n results in stable operation over a wide range of supply Drives LEDs in Boost, Buck Mode, Buck-Boost Mode, and output voltages. A ground referenced voltage FB pin SEPIC or Flyback Topology n serves as the input for several LED protection features, Adjustable Frequency: 100kHz to 1MHz n and also makes it possible for the converter to operate Open LED Protection n as a constant-voltage source. A frequency adjust pin Programmable Undervoltage Lockout with Hysteresis n allows the user to program the frequency from 100kHz Constant-Voltage Loop Status Pin to 1MHz to optimize efficiency, performance or external n PWM Disconnect Switch Driver component size. n CTRL Pin Adjusts High Side Current Sense Threshold n Low Shutdown Current: <1A The LT3956 senses output current at the high side of the n Programmable Soft-Start LED string. High side current sensing is the most flexible n Available in the 36-Lead (5mm 6mm) QFN Package scheme for driving LEDs, allowing boost, buck mode or buck-boost mode configuration. The PWM input provides a acilpp Tsnoi LED dimming ratios of up to 3000:1, and the CTRL input n provides additional analog dimming capability. High Power LED n L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and Battery Charger True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are the n Accurate Current Limited Voltage Regulator property of their respective owners. Protected by U.S. Patents, including 7199560 and 7321203. T lacipy a acilpp Tnoi Efficiency vs V 94% Efficient 25W White LED Headlamp Driver IN V , 6V TO 60V IN D1 22H (80V TRANSIENT) 100 2.2F 2.2F 332k V SW IN s 2 s 5 PGND EN/UVLO 96 100k V ISP REF 332k LT3956 0.68 370mA 92 CTRL INTV ISN CC 40.2k 1M 88 100k FB VMODE 25W LED STRING 16.2k PWM 84 SS RT PWMOUT V GND INTV C CC 80 0 20 60 80 28.7k 40 34k INTV CC 375kHz V (V) IN 47nF 4.7nF 4.7F M1 3956 TA01b 3956 TA01a 3956f EFFICIENCY (%)LT3956 a ulosb T e Mixa Mu M r a Tsgni p ni c no Farugi Tnoi (Note 1) TOP VIEW V , ISP, ISN ..............................................................80V IN SW ............................................................................84V EN/UVLO (Note 3) .....................................................80V 36 35 34 33 32 31 30 INTV ...................................................... V + 0.3V, 8V CC IN NC 1 28 ISP PWMOUT ..................................................INTV + 0.3V EN/UVLO 2 27 ISN CC INTV 3 CTRL, PWM, VMODE ................................................12V CC 37 GND GND FB 4 25 FB ...............................................................................8V 24 GND V , V , SS ................................................................3V C REF V 6 23 PWMOUT IN RT ............................................................................1.5V 38 PGND to GND .........................................................0.5V SW 8 21 SW SW Operating Junction Temperature Range SW SW 9 20 (Note 2) ............................................. 40C to 125C NC 10 12 13 14 15 16 17 Maximum Junction Temperature........................... 125C Storage Temperature Range ................... 65C to 125C Lead Temperature (Soldering, 10 sec) .................. 300C UHE PACKAGE 36-LEAD (5mm s 6mm) PLASTIC QFN T = 125C, = 43C/W, = 5C/W JMAX JA JC EXPOSED PAD (PIN 37) IS GND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 38) IS SW, MUST BE SOLDERED TO PCB ro D re ni Fro Ma Tnoi LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3956EUHE PBF LT3956EUHE TRPBF 3956 40C to 125C 36-Lead (5mm 6mm) Plastic QFN LT3956IUHE PBF LT3956IUHE TRPBF 3956 36-Lead (5mm 6mm) Plastic QFN 40C to 125C Consult LTC Marketing for parts speciefi d with wider operating temperature ranges. *The temperature grade is identiefi d by a label on the shipping container. For more information on lead free part marking, go to: