L1 TP2 GND 6.8µH 74437324068 TP1 U1 LT3909EDD E1 2 VIN 7V-36V E2 R9 (Opt) GND C5 + 10µF 50V 7343 VIN SW C1 R4 1µF 402k 50V 0805 VOUT E3 3 EN/UVLO EN/UVLO FB D1 12 11 SBR1A40S3 (Opt) R2 976k 6 R3 31.6k R5 130k 1 R6 100k 5% R11 (Opt) R8 100k R10 (Opt) R1 4 R12 CTRL 5 1k 5% E5 7 PWM E6 8 FAULT E7 GND R7 (Opt) INTVCC LED1 C3 1µF 24.9k E4 C2 2.2µF 50V 1206 ISET LED2 E9 10 LED1 35V LED 9 LED2 35V LED GND E12 PWM C4 10nF (Opt) * E11 CTRL FAULT * E10 GND GND 13 THE DEMO MANUAL FOR LED * SEE CURRENT RATING E8 GND CUSTOMER NOTICE NOTE: UNLESS OTHERWISE SPECIFIED 1. ALL RESISTORS AND CAPACITORS 0603. 2. ALL RESISTORS ARE 1%. APPROVALS LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES. VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED APP ENG. CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. TECHNOLOGY RB ANDY R LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY TITLE: SCHEMATIC SIZE THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. N/A SCALE = NONE 1630 McCarthy Blvd. Milpitas, CA 95035 www.linear.com Phone: (408)432-1900 Fax: (408)434-0507 IC NO. 2-STRING, 2MHz STEP-UP LED DRIVER WITH ±1.8% CURRENT MATCHING REV. LT3909EDD DEMO CIRCUIT 2176A MODIFY DATE: Jul 29, 2015 2176A_00_REV3 3 SHEET 1 OF 2 R19 R18 0Ω 0805 0Ω 0805 R32 0Ω 0805 R20 0Ω 0805 R31 0Ω 0805 R17 0Ω 0805 R21 0Ω 0805 R30 0Ω 0805 R34 0Ω 0805 R16 0Ω 0805 R22 0Ω 0805 R29 0Ω 0805 R35 0Ω 0805 R15 0Ω 0805 R23 0Ω 0805 R28 0Ω 0805 R36 0Ω 0805 R14 0Ω 0805 R24 0Ω 0805 R27 0Ω 0805 R37 0Ω 0805 R13 0Ω 0805 R25 0Ω 0805 R26 0Ω 0805 R38 0Ω 0805 R40 0Ω 0805 R33 0Ω 0805 R39 0Ω 0805 APPROVALS TECHNOLOGY PCB DES. APP ENG. LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY TITLE: SCHEMATIC SIZE N/A SCALE = NONE 1630 McCarthy Blvd. Milpitas, CA 95035 www.linear.com Phone: (408)432-1900 Fax: (408)434-0507 2-STRING, 2MHz STEP-UP LED DRIVER WITH ±1.8% CURRENT MATCHING IC NO. LT3909EDD REV. 3 DEMO CIRCUIT 2176A MODIFY DATE: Jul 29, 2015 SHEET 2 OF 2