POWER LOSS (W) LT3950 60V, 1.5A LED Driver with Internal Exponential Scale Dimming FEATURES DESCRIPTION n Operates in Boost, SEPIC, Buck Mode and Buck- The LT 3950 is a multitopology DC/DC converter designed Boost Mode specifically to drive high current LEDs. It contains a 1.5A, n 128:1 Internal Exponential Scale PWM Dimming 60V DMOS switch and supports an external PWM dim- n Wide Input Voltage Range (3V to 60V) ming PMOS. The LT3950 has an internal PWM generator n 1.5A, 60V Internal Switch for dimming that maps an analog control signal to an n 20000:1 External PWM Dimming at 100Hz exponential scale used to define PWM dimming duty ratio. n 2% LED Current and Output Voltage Regulation Using an exponential scale to define duty ratio preserves n PMOS Switch Driver for PWM Dimming dimming resolution across a wide range of LED current. n LED Short/Open Protection and Indication In addition to operating as a constant current source, the n Constant Voltage and Constant Current Regulation LT3950 also provides output voltage regulation. This can n Adjustable 300kHz to 2MHz Switching Frequency be used to prevent damage to the part in case of open LED n Adjustable 100Hz to 1kHz PWM Generator Frequency events. A programmable switching frequency offers flex- n Internal Spread Spectrum Frequency Modulation ibility in design for higher efficiency or reduced compo- n Easy Synchronization to External Clock nent size. Enabling spread spectrum frequency modula- n Programmable V UVLO with Hysteresis tion reduces EMI. The switching frequency can also easily IN n Available in 16-Lead MSOP Package be synchronized by driving the SYNC/SPRD pin with an external clock. LED current is programmed with a single external sense resistor and can be adjusted from zero to APPLICATIONS full-scale by an analog signal at the CTRL pin. n Display Backlighting All registered trademarks and trademarks are the property of their respective owners. Protected n Automotive and Avionic Lighting by U.S. Patents, including 7199560, 7321203, 7746300, 8116045. Patents pending. TYPICAL APPLICATION 10W LED Driver for Automotive, 2MHz, 90% Efficient Efficiency and Power Loss with and without PWM Dimming V 10H IN 1 3V TO16V DC 100 3.000 TRANSIENT 2.2F 2.2F TO 48V 96 2.750 V SW ISP IN EFFICIENCY 100% ON 92 2.500 EN/UVLO ISN 88 2.250 100k 1M EFFICIENCY (EFF.) AT 2.000 84 FAULT FAULT FB 10W 10% PWM DIMMING LED 80 1.750 INTV CC 24.9k LT3950 POWER P 10% PWM DIMMING LOSS, EFF. 1F 1.500 76 (DERATED CTRL BELOW 72 1.250 PWMTG V = 7V) IN 267k VC 68 1.000 P 100% ON LOSS PWM 39k 64 0.750 SYNC/SPRD RP RT GND 100k 220pF 60 0.500 300Hz 2MHz 10 13 16 19 22 25 28 31 34 37 40 182k 45.3k V (V) IN 3950 TA01a 3950 TA01b Rev. A 1 Document Feedback For more information www.analog.com EFFICIENCY (%)LT3950 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW V , SW, ISP, ISN, EN/UVLO, FAULT ..........................62V IN ISP 1 16 PWMTG V V ..................................................................2V ISP ISN ISN 2 15 SW FB 3 14 SW INTV , RT, PWMTG .......................................... (Note 2) CC 17 VC 4 13 V IN CTRL 5 GND 12 EN/UVLO VC, RP.................................................. INTV + 200mV CC SYNC/SPRD 6 11 INTV CC PWM 7 10 FAULT SYNC/SPRD, CTRL, PWM, FB .................................5.5V RP 8 9 RT Operating Junction Temperature (Notes 3, 5) MSE PACKAGE 16-LEAD PLASTIC MSOP LT3950E ............................................ 40C to 125C = 40C/W JA LT3950J ............................................. 40C to 150C EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB Storage Temperature Range .................. 65C to 150C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3950EMSE PBF LT3950EMSE TRPBF 3950 16-Lead Plastic MSOP 40C to 125C LT3950JMSE PBF LT3950JMSE TRPBF 3950 16-Lead Plastic MSOP 40C to 150C Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with TRMPBF suffix. Rev. A 2 For more information www.analog.com