REVISION HISTORY REV - 1 2 APPROVED DESCRIPTION PRODUCTION C7, C8 & C9 CHANGE TO "NPO" DATE EDWIN L 11/15/10 EDWIN L 12/14/10 U1 LT3688EFE VIN VIN 7V - 36V ECO E1 6 E2 GND C14 C3 4.7uF 50V 1206 VIN BST1 3 R1 0 Ohm 1000pF 50V R2 C4 0.22uF 24 EN/UVLO SW1 17 WDI DA1 VOUT2 WDE ON FB1 1 16 VOUT1 VOUT1 5V / 800mA D1 DFLS140 5 R3 562K 1% C15 22pF 1 R12 100K 3 OFF R5 100K 15 WDO RUN/SS1 JP1 14 E8 13 7 R6 100K 23 E9 R8 RST1 VOUT2 (1MHz) 49.9K C7 1% R9 100K E10 C8 1000pF 1000pF C9 VIN VIN 21 20 18 RST2 1000pF CONFIG 1 22 E4 R4 107K 1% C5 1000pF RST1 BIAS WDO VOUT1 2 C1 22uF 10V 1206 GND WDE 2 VOUT2 E3 NPIS43LS100MTRF (OPT) E7 WDI L1 10uH 4 BST2 RST2 19 10 C6 0.22uF CONFIG SW2 DA2 FB2 CWDT VOUT2 D2 DFLS140 8 R7 316K 1% C16 22pF 12 RUN/SS2 GND 11 C2 22uF 10V 1206 VOUT2 3.3V / 800mA E6 GND R10 100k 1% CPOR1 CPOR2 E5 NPIS43LS100MTRF SYNC RT L2 10uH 9 C10 1000pF 25 2 3 GND JP2 E11 SYNC R11 100K NOTE: UNLESS OTHERWISE SPECIFIED. 1. ALL RESISTORS ARE IN OHMS, 0402. ALL CAPACITORS ARE IN MICROFARADS, 0402. 2. INSTALL SHUNTS AS SHOWN. OPTIONAL CIRCUIT E12 FB1 L3 CUSTOMER NOTICE VIN VEMI C12 (OPT) 0603 3.3uH C13 (OPT) 1210 + C11 22uF 63V 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. APPROVALS PCB DES. APP ENG. LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY TITLE: SCHEMATIC DUAL MONOLITHIC STEP-DOWN SWITCHING REGULATOR WITH POWER-ON RESET AND WATCHDOG TIMER SIZE C:\PADS PROJECTS\1439A\SCH\1439A_00_REV2.DSN THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. TECHNOLOGY RB EDWIN L N/A SCALE = NONE 1630 McCarthy Blvd. Milpitas, CA 95035 www.linear.com Phone: (408)432-1900 Fax: (408)434-0507 DATE: IC NO. REV. LT3688EFE DEMO CIRCUIT 1439A Tuesday, December 14, 2010 SHEET 2 1 OF 1