1 2 3 4 5 6 7 8 REVISION HISTORY VIN JP1 4 C38 R28 OPT OPT 1 CLKOUT E15 4 DESCRIPTION 3 DATE Circuit change, added parts 08/21/09 MS E5 JP4 R10 VIN+ A J1 0 VIN 40.2K VIN R29 100 R30 100 CLKOUT R7 100K 1% Q1 RJK0305DPB 5 6 7 8 C14 SW1 1nF 5 6 7 8 S1+ S1- R3 4.5V - 14V + J2 2 R27 OPT CIN2 CIN4 10uF OPT Q5 OPT GND E6 VIN- R56 OPT S1+ C37 CIN1 270uF 16V 1 VIN E9 APPROVED 3 PLLIN PHASMD 120 90 60 DEG DEG DEG INTVCC RUN1 JP3 2 A 1 ITEMP1 OPT REV 3 R68 20.0K E1 RUN1 1 ON 2 OFF 3 2 INTVCC MODE PS BM FCM ITEMP2 R26 ECO NOTE 1, TO IMPLEMENT DCR SENSING ON PHASE 1, SHORT RS1. REMOVE R29 AND R30. STUFF R58 WITH A 0 OHM RESISTOR. THE DCR SENSE FILTER CONSISTS OF C14, R56 AND R57. CALCULATE THESE VALUES PER THE DATA SHEET. U1 1nF TRK/SS2 S2- DIFFP 41 SGND 0.1uF VIN R38 RUN2 C49 R43 OPT 20.0K R11 1 2 3 1 2 3 31 32 SW1 CLKOUT VIN 26 INTVCC 25 EXTVCC 24 BG2 23 PGND2 22 BOOST2 21 VIN GND C17 1uF 1 C11 4.7uF 10V Q3 RJK0305DPB BG2 D2 CIN3 CIN5 10uF OPT INTVCC 0 R59 CMDSH-3 4 C21 OPT NOTE 4, ONLY APPLY LOAD FROM J3 TO J4 FOR VOUT1 ONLY APPLY LOAD FROM J5 TO J6 FOR VOUT2 DO NOT CONNECT SCOPE GROUND TO E14 Q7 OPT 4 R60 0.1uF OPT L2 RS2 R39 100 INTVCC R63 OPT OPT 4 R70 0.002 R62 OPT Q4 RJK0330DPB 0 C 0.4uH D3 Q8 OPT OPT 4 1 2 3 OPT OPT 1 R61 VOUT2 COUT4 100uF 6.3V 2010 COUT5 COUT6 + 330uF + 330uF 2.5V 2.5V VOUT2 1.2V / 17A C36 10uF 10V J6 GND S2- R40 100 R12 J5 L2- ILIM2 R69 B EXTVCC 2 OPT J4 VIN 5 6 7 8 OPT VOUT1 1.8V / 17A C32 10uF 10V VO1- INTVCC TG2 RUN2 R41 + COUT3 330uF 2.5V E12 SW2 C48 + COUT2 330uF 2.5V 2.2 R25 0 2010 R58 OPT Q2 RJK0330DPB R18 COUT1 100uF 6.3V S1- 5 6 7 8 BG1 D4 OPT 4 J3 VOUT1 0.002 2 27 4 0.4uH 5 6 7 8 BG1 INTVCC CMDSH-3 1 2 3 PGND1 0 1 2 3 33 PHSASMD 34 MODE/PLLIN 36 37 38 39 35 FREQ R9 28 1 2 3 JP2 29 Q6 OPT OPT 1 2 3 BOOST1 D1 5 6 7 8 ON OFF DIFFN C47 OPT 11 R37 10 TG1 S2+ SENSE2- 30 5 6 7 8 9 C15 5.49K 1% 0 SENSE2+ L1TG1 1 2 3 TK/SS2 8 VO1+ OPT RS1 5 6 7 8 7 TRK/SS2 S2+ E11 R57 1 2 3 ITH2 4 L1 TG2 6 SW2 OPT R36 ITH2 R35 1.5nF E10 VFB2 4 0.1uF 20 C44 R34 5 NC 20.0K VOUT1 VFB2 19 150pF PGOOD2 C43 18 R33 PGOOD1 SGND 17 VFB1 4 20.0K B 16 ITH1 3 ITEMP2 2 VFB1 ILIM2 ITH1 15 R32 ITEMP1 TK/SS1 ILIM1 1 14 TRK/SS1 150pF RUN1 SENSE1- C42 R31 18.2K 1% RUN2 1nF 0.1uF 13 C41 40 C2 SENSE1+ R2 OPT DIFFOUT 0 C20 LTC3855EUJ 12 TRK/SS1 C EXTVCC R64 10 E3 R65 10 EXTVCC EXTVCC E14 C50 VO2_SNSVO2_SNS+ 1uF E2 INTVCC GND INTVCC R42 E13 ILIM1 INTVCC OPT R46 100K 1% E4 NOTE 2, TO IMPLEMENT DCR SENSING ON PHASE 2, SHORT RS2. REMOVE R39 AND R40. STUFF R62 WITH A 0 OHM RESISTOR. THE DCR SENSE FILTER CONSISTS OF C15, R59 AND R60. CALCULATE THESE VALUES PER THE DATA SHEET. R44 OPT R66 100K 1% PGOOD1 PGOOD1 E16 NOTE 3, FOR VOUT2 >= 3.3V, REMOVE R11 AND R70. STUFF R12 AND R69 WITH 0 OHM RESISTORS. PGOOD2 PGOOD2 TEMPERATURE COMPENSATION NETWORK FOR DCR SENSING ITEMP1 VFB1 R50 VFB2 ILIM1 OPT Tooling Holes R52 TRK/SS1 on PCB R71 RN1 ILIM2 R67 ITEMP1 OPT OPT RN3 RN2 R47 OPT TRK/SS2 C52 2 OPT C51 2 OPT RUN2 OPT OPT ITEMP2 LINEAR TECHNOLOGY HASMADE 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. COMPONENTSUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. R53 OPT OPT OPT OPT 1 Represents RUN1 R55 CUSTOMER NOTICE OPT 1 X2 ITH2 R51 OPT 2 R49 ITH1 1 R45 OPTIONAL JUMPERS FOR SINGLE OUTPUT/DUAL PHASE OPERATION X1 1 1 D ITEMP2 OPT THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USEWITH LINEAR TECHNOLOGY PARTS. 1 2 3 4 5 6 CONTRACT NO. APPROVALS PCB DES. ENG. MI MS TECHNOLOGY 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 Fax: (408)434-0507 LTC Confidential-For Customer Use Only TITLE: SCHEMATIC DUAL OUTPUT SYNCHRONOUS BUCK CONVERTER SIZE IC NO. REV LTC3855EUJ 3 DEMO CIRCUIT 1441A DATE: Friday, November 20, 2009 7 SHEET 8 1 OF 1 D