LT3478/LT3478-1 4.5A Monolithic LED Drivers with True Color PWM Dimming FEATURES DESCRIPTIO True Color PWM Dimming Delivers Constant LED The LT 3478/LT3478-1 are 4.5A step-up DC/DC convert- Color with Up to 3000:1 Range ers designed to drive LEDs with a constant current over Wide Input Voltage Range: 2.8V to 36V a wide programmable range. Series connection of the 4.5A, 60m, 42V Internal Switch LEDs provides identical LED currents for uniform bright- Drives LEDs in Boost, Buck-Boost or Buck Modes ness without the need for ballast resistors and expensive Integrated Resistors for Inductor and LED Current factory calibration. Sensing The LT3478-1 reduces external component count and cost Program LED Current: by integrating the LED current sense resistor. The LT3478 100mA to 1050mA (LT3478-1) uses an external sense resistor to extend the maximum (10mV to 105mV)/R (LT3478) SENSE programmable LED current beyond 1A and also to achieve Program LED Current De-Rating vs Temperature greater accuracy when programming low LED currents. Separate Inductor Supply Input Operating frequency can be set with an external resistor Inrush Current Protection from 200kHz up to 2.25MHz. Unique circuitry allows a Programmable Soft-Start PWM dimming range up to 3000:1 while maintaining Fixed Frequency Operation from 200kHz to 2.25MHz constant LED color. The LT3478/LT3478-1 are ideal for Open LED Protection (Programmable OVP) high power LED driver applications such as automotive TFT Accurate Shutdown/UVLO Threshold with LCD backlights, courtesy lighting and heads-up displays. Programmable Hysteresis One of two CTRL pins can be used to program maximum 16-Pin Thermally Enhanced TSSOP Package LED current. The other CTRL pin can be used to program U a reduction in maximum LED current vs temperature to APPLICATIO S maximize LED usage and improve reliability. High Power LED Driver Additional features include inrush current protection, Automotive Lighting programmable open LED protection and programmable , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. soft-start. Each part is available in a 16-pin thermally All other trademarks are the property of their respective owners. Patents Pending. enhanced TSSOP Package. TYPICAL APPLICATIO Automotive TFT LCD Backlight Ef ciency vs V IN 100 10H V 8V TO 16V IN I = 700mA LED f = 500kHz OSC 10F 4.7F PWM DUTY CYCLE = 100% V VLSW IN S 95 SHDN OUT V REF 0.1 R SENSE 45.3k 90 CTRL2 (LT3478) LT3478-1 LED OVPSET 54.9k 85 CTRL1 700mA 15W 130k PWM SS V R C T 6 LEDs LUXEON III (WHITE) 6 LEDs 80 (WHITE) 8 10 12 14 16 1F 0.1F 69.8k V (V) IN PWM DIMMING 3478 TA01b CONTROL 3478 TA01 34781f 1 EFFICIENCY (%) U ULT3478/LT3478-1 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW SW ............................................................................42V SW 1 16 SS V , LED ..................................................................42V OUT SW 2 15 R T V , V , V , SHDN (Note 5) .......................................36V IN S L V 3 14 PWM IN PWM ......................................................................... 15V V 4 13 CTRL2 S 17 CTRL1, 2 .....................................................................6V L 5 12 CTRL1 SS, R , V , V , OVPSET ............................................2V T C REF V 6 11 SHDN OUT Operating Junction Temperature Range LED 7 10 V REF (Notes 2, 3, 4) .................................... 40C to 125C OVPSET 8 9 V C Storage Temperature Range ................... 65C to 150C FE PACKAGE 16-LEAD PLASTIC TSSOP Lead Temperature (Soldering, 10 Sec) .................. 300C T = 125C, = 35C/W JMAX JA EXPOSED PAD (PIN 17) IS PGND, MUST BE SOLDERED TO PCB. ORDER PART NUMBER FE PART MARKING LT3478EFE 3478FE LT3478EFE-1 3478FE-1 LT3478IFE 3478FE LT3478IFE-1 3478FE-1 Order Options Tape and Reel: Add TR Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: