1 2 REVISION HISTORY ECO - 11-15-10 A GND CIN3 2.2uF 100V 1210 CIN4 2.2uF 100V 1210 * 79V CAPACITOR SURGE VOLTAGE E2 R1 1M RUN GND JP1 2 JP2 MODE R2 97.6K 2 PULSE SKIP 4 5 6 BURST BOOST 16 TG 15 2 SHDN VFB SW 14 R6 R4 R5 16.2K 1% R12 C4 100pF 8 FSET R9 49.9K 16V Q1 BSC123N08N 4 D1 BAS521 VOUT E4 R11 VOUT 0 VCC SW VCC C7 1uF 16V 0603 BG PGND 11 SENSE+ 10 TG 0 BG 12 7 SYNC R7 20K C5 1500pF 4.99 D3 1N4148 6 VC (OPT) 143K 1% VCC 13 5 VFB C3 (OPT) C6 0.1uF TG 3 SS 4 BURST_EN R3 5.1M 5% R10 C2 1500pF CONT . 3 LT3845AEFE 1 VIN 100V 1206 3 SHDN 1 U1 C1 0.47uF 8 7 6 5 CIN2 33uF 63V* 1 2 3 CIN1 + 33uF 63V* R13 BG 0 L1 8 7 6 5 + VFB DATE MARTY M. VIN J1 VCC APPROVED PRODUCTION FAB J2 Q2 BSC123N08N 4 1 2 3 VIN 16V - 60V 17 SGND A DESCRIPTION 2 E1 1 VIN REV R16 6.65 1206 VS+ 10uH* D2 B160 J4 R17 VOUT 0.007 2512 COUT1 + 68uF 16V + C9 220pF 100V 1206 COUT2 (OPT) COUT3 22uF 16V 1210 COUT4 (OPT) 1210 J3 GND SENSE- 9 E5 C8 (OPT) R14 0 R15 0 VOUT 12V, 120W GND E3 SYNC R8 100K B B NOTES:UNLESS OTHERWISE SPECIFIED RESISTORS: OHMS, 0402 CAPACITORS: uF, 0402 * L1 LAYOUT PADS ARE NON-STANDARD PADS DESIGNED TO ACCOMMODATE THE WURTH ELEKTRONIC, 74435561100 INDUCTOR OR THE WURTH ELEKTRONIC, 7443551151 INDUCTOR CUSTOMER NOTICE 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. 1 APPROVALS PCB DES. APP ENG. NC MARTY M. TITLE: SCHEMATIC HIGH VOLTAGE SYNCHRONOUS BUCK CONTROLLER WITH ADJUSTABLE OPERATING FREQUENCY SIZE IC NO. N/A SCALE = NONE 2 TECHNOLOGY 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only DATE: 11-15-10 REV. LT3845AEFE DEMO CIRCUIT 1619A 2 SHEET 1 OF 2 1 2 OPTIONAL BIAS CIRCUIT OPTIONAL POWER FETS VIN A VCC A R18 4 R19 Q3B Si1555DL R20 5 Q4 4 1 2 3 3 C13 1uF 6 1 Q3A Si1555DL SW 8 7 6 5 C12 1uF 10V R21 TG BG 2 10V BG R22 Q5 4 1 2 3 1 C11 1uF 10V 2 3 C10 1uF 10V 1 3 2 D5 BAV99 2VOUT 3VOUT D4 BAV99 8 7 6 5 VOUT USE OPTIONAL BIAS CIRCUIT TO BACKFEED VCC WHEN VOUT IS BETWEEN 3V AND 9V AND VCC POWER DISSIPATION EXCEEDS 250mW. REFER TO THE LT3845AEFE DATASHEET FOR MORE DETAILS. B B CUSTOMER NOTICE 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. 1 APPROVALS TECHNOLOGY PCB DES. NC APP ENG. MARTY M. TITLE: SCHEMATIC HIGH VOLTAGE SYNCHRONOUS BUCK CONTROLLER WITH ADJUSTABLE OPERATING FREQUENCY SIZE IC NO. N/A SCALE = NONE 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only DATE: 11-15-10 2 REV. LT3845AEFE DEMO CIRCUIT 1619A 2 SHEET 2 OF 2