5 4 3 2 1 REVISION HISTORY L1 10uH ECO REV 1 2 DESCRIPTION APPROVED DATE M. ZHU 11-05-09 PRODUCTION SUMIDA CDR7D43MN-100 D D U1 LT3991EMSE 0603 3 E1 2 4 + E2 C 1 C2 22uF,100V C3 2.2uF,100V 1210 SANYO 100CE22BS GND JP1 ON OFF R6 OPT 0603 1 2 3 5 BD SYNC BOOST PG SW RT VIN SS EN FB 10 9 8 R1 7 118k (400kHz) 6 R2 562k C5 10pF 11 VIN 4.5V - 55V C1 0.47uF,16V GND D1 DFLS260 2 1 R3 1M E5 R4 200K R7 OPT 0603 C4 47uF,10V E6 1210 GND E8 E7 EN PGOOD E4 E3 EXTSS SYNC R5 100k 0603 B 1 2 3 JP2 C6 OPT 0603 CUSTOMER NOTICE NOTES: UNLESS OTHERWISE SPECIFIED 1. ALL RESISTORS ARE IN OHMS, 0402. ALL CAPACITORS ARE IN MICROFARADS, 0402. A C VOUT [email protected] 2. INSTALL SHUNTS AS SHOWN. CONTRACT NO. LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A APPROVALS CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES. K. TRAN VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL ENG. M. ZHU 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 TECHNOLOGY B SYNC RT FREQ 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 LTC Confidential-For Customer Use Only TITLE: SCHEMATIC A 55V, 1.2A, MICROPOWER BUCK REGULATOR SIZE IC NO. A DATE: REV LT3991EMSE 2 DEMO CIRCUIT 1526A Thursday, November 05, 2009 2 SHEET 1 1 OF 1