5 3 2 1 D3 CMHZ5239B 2 1 E6 9.1V D VIN 1 11 1 GND GND GND Rt 80.6k 1% 500kHz B 3 E8 14 Q1 OPT 4 1 3 2 1 9 PWM VC VADJ RT R4 OPT E7 17 8 15 13 C LED 3 R3 0 E4 1 OUT 2 REF R6 100k 0603 D1 B150 DNC DNC 1210 Q3 MMBT3904 1 LED+ LED- 3 R5 OPT C SW 5 SHDN SUMIDA CDRH8D28 2 16 COUT 2.2uF,50V D4 VC MMSZ5252BS 24V 2 10 SHDN L1 47uH 8 7 6 5 U1 LT3474EFE-1 2 0603 BOOST 6 R1 20k BIAS 7 E2 E3 VADJ CBOOST 0.22uF CIN 2.2uF,50V 1210 12 GND E1 VIN 4 VIN 4V - 36V D R2 10k 0603 2 BIAS 4 Q2 Si2318DS OPT E9 E5 VC GND PWM B C2 0.1uF NOTE: UNLESS OTHERWISE SPECIFIED 1. ALL RESISTORS ARE IN OHMS, 0402. ALL CAPACITORS ARE IN MICROFARADS, 0402. A CUSTOMER NOTICE CONTRACT NO. LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. 5 4 3 APPROVALS DRAWN: TECHNOLOGY KIM T. CHECKED: TITLE: SCHEMATIC DESIGNER: A STEP-DOWN 1A LED DRIVER APPROVED: ENGINEER: KEITH S. 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 LTC Confidential-For Customer Use Only SIZE A DATE: DWG NO. DC1309A * LT3474EFE-1 Wednesday, January 02, 2008 2 SHEET 1 REV A 1 OF 1