DEMO CIRCUIT 1184A QUICK START GUIDE LTC3860EUH DUAL OUTPUT SYNCHRONOUS BUCK CONVERTER DESCRIPTION Demonstration circuit DC1184A is a dual output voltage mode synchronous buck converter featuring the LTC3860EUH. This board provides two outputs of 1.2V/25A and 1.8V/25A from an input voltage of 10V to 14V at a switching frequency of 500kHz. The power stage consists of the Renesas R2J20602NP which is a tri-state PWM compatible 8mm x 8mm DrMOS and a 0.47uH 13.2mm x 12.8mm iron powder type inductor from Wurth. An on-board 5V LT1616 buck regulator provides the 5V bias for the LTC3860 and the DrMOS. The demo board uses a high density, two sided drop-in layout. The power components, excluding the bulk output and input capacitors, fit within a 1.5” x 1.25” area on the top layer. The control circuit resides in a 0.75” x 0.75” area on the bottom layer. The package style for the LTC3860EUH is a 32-lead 5mm x 5mm QFN. Table 1. The main features of the board are listed below: • Differential amplifier for remote sensing VOUT1 which is setup for 1.2V. • Optional components for single output dual phase operation. • CLKIN pin for synchronization to an external clock which can be used in conjunction with optional PHSMD resistors and CLKOUT pin for up to 12-phase operation. • TRACK/SS pins for external coincident rail tracking. • RUN pins and PGOOD pins for each phase. • For each phase, optional footprints for an LTC4449 gate driver and two top FETs and two bottom FETs. Design files for this circuit board are available. Call the LTC factory. Performance Summary (TA = 25°C) PARAMETER CONDITION VALUE Minimum Input Voltage 10V Maximum Input Voltage 14V Output Voltage VOUT1 IOUT1 = 0A TO 25A, VIN = 10V to 14V 1.2V ± 1.75% Output Voltage VOUT2 IOUT2 = 0A TO 25A, VIN = 10V to 14V 1.8V ± 1.75% Nominal Switching Frequency 500kHz Efficiency VOUT1 = 1.2V, IOUT1 = 25A, VIN = 12V 87.8% typical See Figure 2 VOUT2 = 1.8V, IOUT2 = 25A, VIN = 12V 91.0% typical 1 LTC3860EUH QUICK START PROCEDURE Demonstration circuit 1184A is easy to set up to evaluate the performance of the LTC3860EUH. Refer to Figure 1 for the proper measurement equipment setup and follow the procedure below: 1. 2. 3. Place jumpers in the following positions: JP1 RUN1 ON JP2 RUN2 ON JP3 INT 5V ON JP4 +5V SELECT INT With power off, connect the input power supply to VIN and GND. Turn on the power at the input and increase the input voltage to 10V or higher. Check for the proper output voltages: Vout1 = 1.179V to 1.221V Vout2 = 1.769V to 1.832V 4. Once the proper output voltages are established, adjust the loads within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. Do not apply load between the VOS1+ and VOS1- pins or between the VO2+ and VO2- pins. These pins are only intended to sense the output voltage across COUT4 and COUT10 respectively. Heavy load currents applied across these pins may damage the converter. Note 1. Use J9 and J10 to monitor the output voltage ripple. J9 will measure the ripple across COUT2 and J10 will measure the ripple across COUT8. Connect J9 and J10 to the oscilloscope with a short coaxial cable. To avoid excessive noise pickup, keep the length of the cable to a minimum. Note 2. SINGLE OUTPUT / DUAL PHASE OPERATION A single output / dual phase converter may be preferred for high output current applications. The benefits of single output / dual phase operation is lower ripple current through the input and output capacitors, improved load step response and simplified thermal design. To implement single output / dual phase operation, make the following modifications: 1. Select phase 1 to be the master and phase 2 the slave since the differential amplifier already senses VOUT1. 2. Stuff R16 with 0 Ohms to disable the error amp for phase 2. 3. Stuff 0 Ohms at R49 to tie COMP1 to COMP2 and remove the redundant compensation components. 4. Stuff R20 with 0 Ohms. 5. Remove 0 Ohm resistor at R25 to release IAVG from ground. 6. Stuff C16 with 100pF to filter the IAVG signal. 7. Stuff R60 with 0 Ohms to tie the two RUN pins together. 8. Stuff R57 with 0 Ohms to tie the two TRK/SS pins together. 9. Tie VOUT1 to VOUT2 by tying together the exposed copper pads on the VOUT shapes with pieces of heavy copper foil. 2 LTC3860EUH VOUT1 + V - IIN A + VOUT1 load IOUT1 A VIN supply A + + VOUT2 load IOUT2 - + VIN V - + V - VOUT2 Figure 1. Proper Measurement Equipment Setup DC1184A Efficiency at Vin = 12V, Fsw = 500kHz 95 1.8V 90 Efficiency 1.2V 85 80 Parameters and conditions: ● DrMOS = Renesas R2J20602NP. ● L = Wurth 744355147 (0.47uH, DCR= 0.67mOhms +/- 10%). ● No external bias applied; 5V bias for LTC3860 and DrMOS supplied from on-board 5V LT1616 buck converter. ● Other rail disabled. ● No airflow. 75 70 0 5 10 15 20 25 30 Load current (Amps) Figure 2. Typical Efficiency Curves 3 E28 DRMBIAS E19 GND E15 CLKOUT E12 TRK/SS2 E13 CLKIN E8 TRK/SS1 E5 PGOOD1 E4 PGOOD2 OFF ON OFF 3 2 JP2 0 R9 R28 (Opt) 0 R24 (Opt) R51 (Opt) R50 R57 (Opt) VDIF1 DRMBIAS2 0 R71 R1B 20K 1% R3A 499 1% C3A 2200pF R77 10.0K 1% R76 30.1K 1% C1A C1B R49 (Opt) VOS1+ VOS1- VDIF1 VCC 7 6 5 4 3 8 33 29 30 R19 (Opt) COMP1 2 VCC R29 C14 0.1uF FB2 SGND SGND SGND COMP2 VSNSP VSNSN VSNSOUT COMP1 FB1 1uF C7 C6 0.1uF (Opt) R30 40.2K 1% Fswitch = 500kHz typical C3B 2200pF R3B 499 1% 100pF 6.34K 1% C2B 680pF R2B 100pF R12 (Opt) R8 (Opt) VOUT2 U1 LTC3860EUH 6.34K 1% C2A 680pF R2A VIN VCC C17 (Opt) R34 (Opt) (Opt) R33 23 24 PWMEN1 C16 (Opt) 31 16 19 20 21 22 25 R25 0 (Opt) PWM1 R32 (Opt) PWM2 R53 (Opt) 0 TP3 TP2 TP4 DISBL# NC NC PWM VIN 55 R23 10.0K C12 1uF 25V DRMBIAS2 2 53 56 55 2 53 56 DRMDISBL2 VIN C10 0.22uF C9 0.22uF TP1 R17 VCC R27 (Opt) R52 (Opt) R7 (Opt) DRMDISBL1 R26 59.0K 1% R20 (Opt) VCC C11 (Opt) PWMEN2 VINSNS PWM2 ISNS2P ISNS2N ISNS1N ISNS1P PWM1 R13 59.0K 1% R10 (Opt) VCC R54 (Opt) R5 DRMDISBL2 VCC R2 10.0K C2 1uF 25V DRMBIAS1 NC NC PWM DISBL# 6. STUFF R60 WITH 0 OHMS. 7. STUFF R57 WITH 0 OHMS. 8. REMOVE REDUNDANT COMPENSATION COMPONENTS. 9. TIE VOUT1 AND VOUT2 SHAPES TOGETHER. 1. FOR VOUT1, APPLY EXCITATION SIGNAL ACROSS R6. 2. FOR VOUT2, APPLY EXCITATION SIGNAL ACROSS R71 AND CHANGE ITS VALUE TO 10 OHMS. BODE PLOT SETUP: 1. STUFF R16 WITH 0 OHMS. 2. STUFF R49 WITH 0 OHMS. 3. STUFF R20 WITH 0 OHMS. 4. REMOVE 0 OHM RESISTOR AT R25. 5. STUFF C16 WITH 100PF. MODIFICATIONS FOR SINGLE OUTPUT / DUAL PHASE OPERATION WHERE PHASE 1 = MASTER: RBB 10.0K 1% R16 (Opt) VCC RBA 20K 1% R1A 20K 1% R75 10.0K 1% R15 (Opt) VCC 0 R70 VOUT2 COMP1 R60 (Opt) DRMBIAS1 R61 (Opt) R3 100K C4 1000pF C1 1000pF R4 100K VCC R21 10.0K VCC 3 2 RUN2 1 JP1 RUN1 1 4 ON R1 2.2 7 GH NOTE: UVL0 = 9V, Typical 32 58 VIN VLDRV 2.2 R18 VDRIVE VDRIVE VIN C8 4.7uF 10V 0805 VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH C3 1uF 25V X5R U2 R2J20602NP VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH VSWH C13 1uF 25V X5R 0603 U3 R2J20602NP 59 21 40 41 42 43 44 45 46 47 48 49 50 CIN8 22uF 16V 59 21 40 41 42 43 44 45 46 47 48 49 50 CIN2 22uF 16V 1210 SW2 C15 0.22uF R73 0 CIN7 22uF 16V L2 1. ALL RESISTORS ARE IN OHMS, 0603. 2. ALL CAPACITORS ARE IN MICROFARAD, 0603. R63 1.00K 1% VOUT2 0.47uH 744355147 Wurth Electronik R31 2.87K 1% R62 1.00K 1% VOUT1 VIN L1 0.47uH 744355147 Wurth Electronik R11 2.87K 1% SW1 C5 0.22uF R72 0 CIN1 22uF 16V 1210 CIN3 (Opt) 1210 VOUT2 R14 10 COUT10 100uF 6.3V COUT11 (Opt) 1210 COUT5 (Opt) 1210 R6 10 E3 VOS1+ VOS1E11 COUT4 100uF 6.3V VOS1- VOUT1 VOS1+ + + CIN6 180uF 16V (Opt) COUT2 330uF 2.5V 7343 + + + COUT3 330uF 2.5V 7343 CIN5 180uF 16V 16SVP180MX J5 VOUT1- J4 VOUT1+ 1.2V / 25A E2 VIN- J2 GND J1 VIN 10V - 14V E20 VO2- E14 VO2+ + COUT7 330uF 2.5V 7343 + COUT8 330uF 2.5V 7343 + COUT9 330uF 2.5V 7343 J8 VOUT2- J7 VOUT2+ 1.8V / 25A 5. USE E14 AND E20 TO MONITOR THE DC VOLTAGE OF VOUT2 WITH ANY DMM. 4. USE E3 AND E11 TO MONITOR THE DC VOLTAGE OF VOUT1. ONLY USE A BATTERY POWERED DMM. 3. DO NOT CONNECT SCOPE GROUND TO E11. 2. ONLY APPLY LOAD FROM J7 TO J8 ON VOUT2. NOTE: 1. ONLY APPLY LOAD FROM J4 TO J5 ON VOUT1. COUT1 330uF 2.5V 7343 CIN4 (Opt) 1210 E1 VIN+ 04/14/10 Mike S. VIN 01/11/10 Mike S. Value Change: R74, R76, Q1, Q2, Q11 & Q12. DATE 06/22/09 APPROVED Mike Shriver 6 DESCRIPTION PRODUCTION Value Change: R2A, R2B, R30, R26, R13, COUT17, COUT22, C30 & C31. (FSwitch 400kHz to 500kHz) 4 - REVISION HISTORY 5 REV NOTE: UNLESS OTHERWISE SPECIFIED. C18 4.7uF 10V 0805 5 BOOT R74 30.1K 1% 1 9 VIN 14 VCC 27 SS2 11 SS1 CLKIN 26 PWMEN1 17 PGOOD2 FREQ 10 PGOOD1 CLKOUT 12 RUN2 PHSMD 13 RUN1 IL1M1 IAVG 28 ILIM2 18 PWMEN2 15 CGND 57 CGND 57 VCIN 4 VCIN 1 6 51 GL 52 CGND CGND CGND 1 6 51 7 3 GH CGND CGND CGND 8 9 10 11 12 13 14 15 16 17 18 19 20 VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN GL 58 VIN VLDRV 3 54 Reg5V 8 9 10 11 12 13 14 15 16 17 18 19 20 VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN VIN 52 54 Reg5V PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 5 BOOT PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND PGND 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 ECO LTC3860EUH 4 OFF ON C24 1uF R40 2.2 VDRIVE C21 1uF R35 2.2 VDRIVE 4 5 6 7 GND IN VLOGIC VCC 9 GND BG TS TG BOOST 3 2 1 8 0 R64 C20 0.22uF 4 Q6 RJK0330DPB 4 Q1 RJK0305DPB 1 2 3 5 1 2 3 5 4 4 Q2 RJK0305DPB 1 2 3 5 1 2 3 5 3 2 JP3 INT 5V1 VIN PWM2 0805 4.7uF C22 4 5 6 7 D6 C26 1uF GND IN VLOGIC VCC 2 4 5 9 GND BG TS TG BOOST 3 2 1 8 GND SHDN VIN FB SW BOOST U6 LT1616ES6 U5 LTC4449EDCB CMDSH-3 3 6 1 0 R65 R45 6.65K 1% R46 20K 1% C25 0.22uF 4 1 2 3 5 15uH A914BYW-150M D4 B0530W-7-F L3 5 1 2 3 CMDSH-3 D3 4 Q13 RJK0330DPB 5V BIAS 0.22uF C23 Q11 RJK0305DPB C27 10uF 10V 0805 5 1 2 3 5 1 2 3 VCC C28 1uF 4 4 Q12 RJK0305DPB CIN9 22uF 16V 1210 10 R47 Q14 RJK0330DPB SW2 VIN VIN CIN12 22uF 16V 1210 CIN10 22uF 16V 1210 3 0 C29 1uF R48 EXT JP4 +5V SELECT 1 INT 2 CIN11 22uF 16V 1210 Q7 RJK0330DPB SW1 OPTIONAL DISCRETE GATE DRIVER AND MOSFETS FOR PHASE 2 PWM1 4.7uF 0805 C19 U4 LTC4449EDCB CMDSH-3 D5 OPTIONAL DISCRETE GATE DRIVER AND MOSFETS FOR PHASE 1 VDRIVE E26 GND E25 VDRIVE R37 10.0K GND ISTEP1 JP5 10mV / A 5% DUTY CYCLE MAX. PULSED LOAD1 CURRENT R39 0.010 1% 2010 Q4 SUD50N03-12P R41 10.0K R68 (Opt) PWMEN2 R66 (Opt) PWMEN1 (Opt) R69 (Opt) R67 DRMDISBL2 DRMDISBL1 PWM ENABLE CIRCUIT FOR NON-THREE STATE COMPATIBLE DRMOS E24 GND E23 PULSE GEN2 5% DUTY CYLCE MAX. GND ISTEP2 JP6 10mV / A 5% DUTY CYCLE MAX. PULSED LOAD2 CURRENT R44 0.010 1% 2010 Q9 SUD50N03-12P DYNAMIC LOAD CIRCUIT FOR VOUT2 E22 GND E21 PULSE GEN1 5% DUTY CYLCE MAX. DYNAMIC LOAD CIRCUIT FOR VOUT1 + + COUT18 (Opt) 7343 COUT13 (Opt) 7343 + + COUT19 (Opt) 7343 COUT14 (Opt) 7343 + + COUT20 (Opt) 7343 COUT15 (Opt) 7343 COUT21 (Opt) 1210 COUT16 (Opt) 1210 VOUT1 COUT22 100uF 6.3V 1210 VOUT2 COUT17 100uF 6.3V 1210 C31 4.7uF 10V (Opt) 0805 C30 4.7uF 10V (Opt) 0805 J10 J9 VOUT2 VOUT1 LTC3860EUH 5