LT3909 2-String 60mA, 2MHz Step-Up LED Driver with 2% Current Matching FEATURES DESCRIPTION n Up to 36V of LEDs, 2-String 60mA LED Driver The LT 3909 is a 2-string 60mA LED driver with a fixed n Wide Input Range: 2.9V to 40V 2MHz step-up DC/DC converter capable of driving up to 36V n Up to 40,000:1 PWM Dimming (250ns LED On-Time) of LEDs. Each LED string contains an accurate high-side (Independent of Leakage at V ) current source with 2% current matching. Output volt- OUT n 2% LED Current Matching (Typ 0.3%) age adapts to variations in LED V for optimum efficiency. F n Integrated Schottky Diode Maximum LED current can be programmed from 10mA n Internal 400m, 40V, 1A Switch to 60mA per string using a single resistor. LED brightness n Single Resistor Sets LED Current (10mA to 60mA) can be reduced with analog dimming (up to 10:1) or with for Both High-Side Current Sources PWM dimming (up to 40,000:1 at 100Hz, up to 160:1 at n Output Adapts to LED V for Optimum Efficiency F 25kHz) (independent of leakage at V ). The LED pins OUT n LED Current Regulated Even for V > V IN OUT can be paralleled for higher LED current. n Fault Flag + Protection for Open-LED and LED-Short- to-GND (Other String Remains in Regulation) Additional features include: programmable maximum V OUT n Programmable Maximum V (Regulated) for open LED protection, a fault flag to indicate open-LED OUT n Internal Compensation, Soft-Start and Thermal or LED-short-to-GND and an internal regulation loop to Regulation safely limit junction temperature. The LT3909 also includes n Accurate EN/UVLO Threshold internal compensation, internal soft-start and micropower n Fixed 2MHz Switching Frequency shutdown. The LT3909 is available in the 12-pin (3mm 3mm) DFN and 12-pin MSOP packages. APPLICATIONS L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear n PDAs, Handheld Computers Technology Corporation. All other trademarks are the property of their respective owners. n GPS Receivers n Automotive Displays n High Contrast Instrument Clusters TYPICAL APPLICATION 2-String 40mA, 2MHz LED Driver for Ten White LEDs/String LED Current Waveforms 6.8H 20,000:1 PWM Dimming (100Hz) V IN 7V TO 36V V = 12V 1F 2.2F IN 976k SW V OUT V FB IN I(LED1) 20mA/DIV 31.6k 402k LT3909 EN/UVLO LED1 130k I(LED2) PWM LED2 20mA/DIV CTRL FAULT V IN PWM 100k INTV GND I CC SET 2V/DIV 10 LEDs PER STRING 3909 TA01b 400ns/DIV 24.9k 1F 3909 TA01a 3909fb 1 For more information www.linear.com/LT3909LT3909 ABSOLUTE MAXIMUM RATINGS (Note 1) V , V , SW ...........................................................40V Operating Junction Temperature (Notes 3, 4) IN OUT LED1, LED2 ...............................................................40V LT3909E, LT3909I ............................. 40C to 125C V LED1, V LED2 .......................................40V Storage Temperature Range .................. 65C to 150C OUT OUT EN/UVLO, FAULT .......................................................40V Lead Temperature (Soldering, 10 sec) CTRL, FB, PWM ..........................................................6V MSOP Package Only .............................................300C INTV , I ....................................................... (Note 2) CC SET PIN CONFIGURATION TOP VIEW TOP VIEW 1 SW INTV 12 CC INTV 1 12 SW CC V 2 11 V OUT IN V 2 11 V IN OUT 3 EN/UVLO 10 LED1 EN/UVLO 3 10 LED1 13 13 GND I 4 GND 9 LED2 4 9 LED2 SET I SET CTRL 5 8 FAULT 5 8 CTRL FAULT FB 6 7 PWM 6 7 FB PWM MSE PACKAGE DD PACKAGE 12-LEAD PLASTIC MSOP 12-LEAD (3mm 3mm) PLASTIC DFN = 40C/W, = 5C/W to 10C/W JA JC = 43C/W, = 5.5C/W JA JC EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION (