DEMO MANUAL DC1822B LTC3861EUHE High Current, Dual Output Synchronous Buck Converter DESCRIPTION Demonstration circuit 1822B is a dual output synchronous buck converter featuring the LTC(R)3861EUHE. The board provides two outputs of 1.5V/25A and 1.2V/25A from an input voltage of 7V to 14V at a switching frequency of 500kHz. The power stage consists of a 6mm x 6mm DrMOS and a 13mm x 13mm iron powder type inductor. An on-board 5V LT(R)3470 buck regulator provides the 5V bias for the LTC3861 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 1.2" area on the top layer. The control circuit fits in a 1.1" x 1.0" area on the bottom layer. The package style for the LTC3861EUHE is a 36-lead 5mm x 6mm QFN. All registered trademarks and trademarks are the property of their respective owners. PERFORMANCE SUMMARY PARAMETER The main features of the board are: * Remote sensing for each output, where the divider is placed before a high input impedance differential amplifier. * CLKIN and CLKOUT pins. * Optional resistors to tie the two outputs together. * Connector and header to tie two or more boards together for up to 12-phase operation. * Optional footprint for an LTC4449 gate driver and discrete MOSFETs. * Optional footprint for a dual phase Delta power block. Design files for this circuit board are available. (TA = 25C), no airflow CONDITION VALUE Minimum Input Voltage 7V Maximum Input Voltage 14V Output Voltage VOUT1 IOUT1 = 0A to 25A, VIN = 7V to 14V 1.5V 2% Output Voltage VOUT2 IOUT2 = 0A to 25A, VIN = 7V to 14V 1.2V 2% VOUT1 Maximum Output Current, IOUT1 VIN = 7V to 14V, VOUT1 = 1.5V 25A VOUT2 Maximum Output Current, IOUT2 VIN = 7V to 14V, VOUT2 = 1.2V 25A Nominal Switching Frequency Efficiency (See Figure2 and Figure3) 500kHz VOUT1 = 1.5V, IOUT1 = 25A, VIN = 12V 91.6% Typical VOUT2 = 1.2V, IOUT2 = 25A, VIN = 12V 90.7% Typical Note: The DC1828B demo circuit and manual replaces the DC1828A. The demo board was modified slightly. Rev 0 1 DEMO MANUAL DC1822B QUICK START PROCEDURE Demonstration circuit 1822B is easy to set up to evaluate the performance of the LTC3861EUHE. Please refer to Figure1 for proper measurement equipment setup and follow the procedure below. 3.Next, apply 25A load to each output and re-measure VOUT. 4.Once the DC regulation is confirmed, observe the output voltage ripple, load step response, efficiency and other parameters. 1.With power off, connect the input supply, load and meters, as shown in Figure1. Preset the load to 0A and VIN supply to be 0V. Place jumpers in the following positions: NOTE 1. Use the BNC connectors labeled VOUT1 or VOUT2 to measure the output voltage ripple. NOTE 2. Do not apply the load from the VOS1+ turret to the VOS1- turret or from the VOS2+ turret to the VOS2- turret. These are connected to the sense traces for the output voltage. Heavy load currents applied across these turrets may damage these traces. JP1RUN1ON JP2RUN2ON JP3 INT BIAS ON 2.Adjust the input voltage to be between 7V to 14V. VOUT1 should be 1.5V 2%.VOUT2 should be 1.2V 2%. - VOUT1 LOAD + + A A IOUT1 VOUT2 LOAD - IOUT2 Monitor voltage across COUT5 and COUT10 for accurate efficiency measurements. + + VOUT1 * VOUT2 V V - - * + VIN V - dc1822b F01 IIN A + VIN SUPPLY - Figure1. Proper Measurement Equipment Setup Rev 0 2 DEMO MANUAL DC1822B QUICK START PROCEDURE DYNAMIC LOAD CIRCUIT (OPTIONAL) 1.Preset the amplitude of a pulse generator to 0.0V and the duty cycle to 5% or less. 2.Connect the scope to the VOUT BNC connectors for the rail under test with a coax cable. To monitor the load step current, connect the scope probe across the ISTEP turrets for that rail. 3.Connect the output of the pulse generator to the PULSE GEN turret for the rail under test and connect the return to one of the GND turrets. 4.With the converter running, slowly increase the amplitude of the pulse generator output to provide the desired load step pulse height. The scaling for the load step signal is 10mV/Amp. See Figure4 and Figure5 for transient response curves with a 50% load change. 95 Efficiency (%) 90 85 Parameters and conditions: RBOOST = 2.2 (R2, R25) L = Wurth 744355147 (0.47H, DCR = 0.67m 10%) External 5V bias applied Power from the external 5V bias included in the efficiency measurements 1.2V rail disabled No airflow 80 75 70 0 5 10 15 Load Current (Amps) VIN = 7V VIN = 12V 20 25 VIN = 14V 30 dc1822b F02 Figure2. Efficiency Curves for the 1.5V Rail of the DC1822B. fSW = 500kHz with the FDMF6820A DrMOS 95 Efficiency (%) 90 85 Parameters and conditions: RBOOST = 2.2 (R2, R25) L = Wurth 744355147 (0.47H, DCR = 0.67m 10%) External 5V bias applied Power from the external 5V bias included in the efficiency measurements 1.5V rail disabled No airflow 80 75 70 0 5 10 15 Load Current (Amps) VIN = 7V VIN = 12V 20 25 VIN = 14V 30 dc1822b F03 Figure3. Efficiency Curves for the 1.2V Rail of the DC1822B. fSW = 500kHz with the FDMF6820A DrMOS Rev 0 3 DEMO MANUAL DC1822B QUICK START PROCEDURE 88mV 1.5VO(AC) 50mV/DIV 25A LOAD STEP 5A/DIV 12.5A 20s/DIV dc1822b F04 Figure4. Load Step Response of the DC1822B 1.5V Rail at VIN = 12V. COUT = 3x Sanyo 2R5TPE330M9 || 2x 100F X5R 6.3V 1210, L = 0.47H, fSW = 500kHz 91mV 1.2VO(AC) 50mV/DIV 25A LOAD STEP 5A/DIV 12.5A 20s/DIV dc1822b F05 Figure5. Load Step Response of the DC1822B 1.2V Rail at VIN = 12V. COUT = 3x Sanyo 2R5TPE330M9 || 2x 100F X5R 6.3V 1210, L = 0.47H, fSW = 500kHz SINGLE OUTPUT/DUAL PHASE OPERATION A single output/dual phase converter may be preferred for higher output current applications. The optional components required to tie the phases together are found on the bottom of the schematic shown in Figure8. To tie the two outputs together, make the following modifications: 1.Stuff 0 at R36 and R47 to tie the two outputs together. 2.Select one rail to be the master. * If VOUT1 is the master, then stuff 0 at R51 to disable the error amplifier for phase 2. Also stuff 0 at R52. * If VOUT2 is the master, then stuff 0 at R49 to disable the error amplifier for phase 1. Also stuff 0 at R50. 3.Remove the 0 jumper at R13 and stuff a 100pF capacitor at C14 for the IAVG signal. 4.Stuff 0 at R53, R48 and R54 to tie the COMP, TRK/SS and RUN pins together. 5.Remove the redundant compensation components. PARALLELING BOARDS The DC1822B demo boards can be tied together to form a converter with up to 12 phases. To tie the boards together, place the boards side-by-side and then connect the boards by connecting J8 of one board to J9 of the other. This will connect the IAVG, COMP, TRK/SS and signal ground signals together. Next, use copper strips to tie the VOUT planes, the VIN planes and GND planes of the two adjacent boards together. The board has exposed copper along the edges of the board for this purpose. Figure6 shows how to set up a 4-phase converter and Figure7 shows how to set up a 3-phase plus single phase converter. Rev 0 4 Cu VIN VOUT 0.0m 0.0m BOARD #1 BOARD #2 VOUT1 TO VOUT2 R36 & R47 NS NS ILIM1 TO VCC R50 0 0 NS NS ILIM2 R R24 0 NS FB1 TO VCC R49 0 0 FB2 TO VCC R51 0 0 TRK/SS1 TO TRK/SS2 R48 0 0 COMP1 TO COMP2 R53 0 0 RUN1 TO RUN2 R54 Figure6. Setup of a 4-Phase Converter; Phase 1 of Board 1 is the Master STUFF STUFF ILIM1 R R17 ILIM2 TO VCC R52 Note: Tie GND shapes together on the bottom layer by using the exposed copper along the edge of the board. VIN VOUT BOARD 2--TOP LAYER Cu VIN VOUT BOARD 1--TOP LAYER NS NS NS NS PHASE MODE SETTING R41 R42 VOUT 100pF dc1822a F06 NS NS IAVG PIN R13 100pF C14 DEMO MANUAL DC1822B QUICK START PROCEDURE Rev 0 5 6 VIN Cu VIN VOUT1 NS BOARD #2 NS NS ILIM1 TO VCC R50 STUFF STUFF ILIM1 R R17 NS 0 ILIM2 TO VCC R52 STUFF NS ILIM2 R R24 0 NS FB1 TO VCC R49 NS 0 FB2 TO VCC R51 NS 0 TRK/SS1 TO TRK/SS2 R48 NS 0 COMP1 TO COMP2 R53 NS 0 RUN1 TO RUN2 R54 0 NS NS NS PHASE MODE SETTING R41 R42 Single phase rail VOUT2 Figure7. Setup of a 3-Phase Plus Single Phase Converter; Phase 1 of Board 1 Is the Master of the 3-Phase Rail 0.0m BOARD #1 VOUT1 TO VOUT2 R36 & R47 Note: Tie GND shapes together on the bottom layer by using the exposed copper along the edge of the board. Triple phase rail VOUT1 BOARD 2--TOP LAYER Cu VIN VOUT1 BOARD 1--TOP LAYER 100pF dc1822a F07 NS NS IAVG PIN R13 100pF C14 DEMO MANUAL DC1822B QUICK START PROCEDURE Rev 0 DEMO MANUAL DC1822B PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER DC1822B Required Circuit Components 1 4 C1, C7, C8, C9 CAP, 0.22F, 10%, 25V, X7R, 0603 AVX 06033C224KAT2A 2 2 C1-1, C1-2 CAP, 1500pF, 10%, 50V, GOG, 0603 MURATA,GRM1885C1H152JA01D 3 2 C2-1, C2-2 CAP, 100pF, 5%, 25V, NPO, 0603 AVX 06033A101JAT2A 4 2 C28, C29 CAP, 10F, 20%, 6.3V, X5R, 0805 AVX 08056D106MAT2A 5 4 C3, C11, C34, C35 CAP, 2.2F, 10%, 16V, X7R, 0603 MURATA GRM188R61C225KE15D 6 2 C3-1, C3-2 CAP, 3300pF, 10%, 50V X7R, 0603 AVX 06035C332KAT2A 7 1 C6 CAP, 1F, 20%, 25V, X5R, 0603 AVX 06033D105MAT2A 8 1 CIN2 CAP, 180F, 20%, 16V, OSCON SANYO 16SVP180MX 9 4 CIN3, CIN4, CIN5, CIN6 CAP, 22F, 20%, 16V, X5R, 1210 AVX 1210YD226MAT2A 10 6 COUT1-COUT3, COUT6-COUT8 CAP, 330F, 20%, 2.5V POSCAP 7343 SANYO 2R5TPE330M9 11 4 COUT4, COUT5, COUT9, COUT10 CAP, 100F, 20%, 6.3V, X5R, 1210 AVX 12106D107MAT2A 12 2 L1,L2 IND, 0.47H, 20% WURTH 744355147 13 2 R1, R45 RES, 18.2k, 1%, 1/10W, 0603 VISHAY CRCW060318K2FKEA 14 4 R11, R18, R39, R43 RES, 10, 1%, 1/10W, 0603 VISHAY CRCW060310R0FKEA 15 2 R17, R24 RES, 53.6k, 1%, 1/10W, 0603 VISHAY CRCW060353K6FKEA 16 2 R2, R25 RES, 2.2, 1%, 1/16W, 0603 VISHAY CRCW06032R20FKEA 17 2 R20, R38 RES, 2.87k, 1%, 1/10W, 0603 VISHAY CRCW06032K87FKEA 18 1 R2-1 RES, 9.76k, 1%, 1/16W, 0603 VISHAY CRCW06039K76FKEA 19 1 R2-2 RES, 9.31k, 1%, 1/16W, 0603 VISHAY CRCW06039K31FKEA 20 3 R3, R16, R26 RES, 1, 1%, 1/10W, 0603 YAGEO RC0603FR-071RL 21 2 R3-1, R3-2 RES, 280, 1%, 1/10W, 0603 VISHAY CRCW0603280RFKEA 22 1 R37 RES, 34k, 1%, 1/10W, 0603 VISHAY CRCW060334K0FKEA 23 2 R8, R44 RES, 100k, 1%, 1/10W, 0603 VISHAY CRCW0603100KFKEA 24 9 R9, R12, R13, R19, R21-R23, R32, R73 RES, 0, JUMPER, 0603 VISHAY CRCW06030000Z0EA 25 11 RB-1, RB-2, RT-2, R1-1, R1-2, R4-R6, R29, R30, R46 RES, 10k, 1%, 1/10W, 0603 VISHAY CRCW060310K0FKEA 26 1 RT-1 RES, 15k, 1%, 1/10W, 0603 YAGEO RC0603FR-0715KL 27 1 U1 I.C., LTC3861EUHE ANALOG DEVICES LTC3861EUHE#PBF 28 2 U2, U3 MOSFET, DrMOS, DC-DC, 3.3V, PWM FAIRCHILD FDMF6820A Additional Circuit Components 1 1 C17 CAP, 0.22F, 10%, 25V, X7R, 0603 AVX 06033C224KAT2A 2 1 C18 CAP, 1F, 20%, 25V, X5R, 0603 AVX 06033D105MAT2A 3 1 C19 CAP, 22F, 20%, 16V, X5R, 1210 AVX 1210YD226MAT2A 4 2 C2, C4, C5, C10, C12-C16, C20, C22C25, C27, C30-C33 CAP, 0603 OPT 5 1 C21 CAP, 22pF, 10%, 25V, NPO, 0603 AVX 06033A220KAT2A 6 1 C26 CAP, 1F, 20%, 25V, X5R, 0603 AVX 06033D105MAT2A 7 0 CIN1 CAP, SVP, F8 OPT 8 0 CIN7-CIN14, COUT11-COUT17 CAP, 1210 OPT 9 0 COUT15-COUT17, COUT22-COUT24 CAP, 7343 OPT 10 0 D1 DIODE, BAV170, SOT23 OPT Rev 0 7 DEMO MANUAL DC1822B PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER 11 0 D2, D3 CMDSH-3 OPT 12 1 L3 IND, 33H, -53DLC TOKO A914BYW-330M=P3 13 0 L4 INDUCTOR, -53LDC OPT 14 0 PB1 DC/DC Converters, D12S1R845A OPT 15 2 Q1, Q2 MOSFET, 30V N-CHANNEL, DPAK VISHAY SUD50N03-12P-E3 16 0 Q3, Q4, Q7, Q8 BSC050NE2LS OPT 17 0 Q5, Q6, Q9, Q10 BSC010NE2LS OPT 18 0 R10, R14, R15, R27, R28, R31, R33R35, R41, R42, R47-R55, R62, R64R67, R69, R71, R72, R74-R81 RES, 0603 OPT 19 2 R56, R58 RES, 10k, 1%, 1/10W, 0603 VISHAY CRCW060310K0FKEA 20 2 R57, R60 RES, 0.010, 1%, 1W, 2010 IRC LRC-LRF2010LF-01-R010-F 21 1 R59 RES, 0, JUMPER, 1206 VISHAY CRCW12060000Z0EA 22 1 R61 RES, 604k, 1%, 1/16W, 0603 VISHAY CRCW0603604KFKEA 23 1 R63 RES, 200k, 1%, 1/16W, 0603 VISHAY CRCW0603200KFKEA 24 1 U4 BUCK REGULATOR, LT3470ETS8 ANALOG DEVICES LT3470ETS8 25 0 U5 BUCK REGULATOR, LT3470ETS8 OPT 26 0 U8, U9 N-CHANNEL MOSFET DRIVER, LTC4449 OPT 1 27 E1-E27 TESTPOINT, TURRET, 0.095" MILL-MAX 2501-2-00-80-00-00-07-0 2 6 J1-J6 STUD, TEST PIN PEM KFH-032-10 3 12 J1-J6 NUT, BRASS PL #10-32 ANY #10-32M/S 4 6 J1-J6 RING, LUG #10 KEYSTONE 8205 5 6 J1-J6 WASHER, TIN, PLATED BRASS ANY 6 2 J7, J10 CON, BNC, 5 PINS CONNEX 112404 7 1 J8 HEADER, DOBL ROW, RT ANGLE, 2x4, 8 PIN MILL-MAX 802-10-008-20-001000 8 1 J9 SOCKET, DBL ROW, RT ANGLE, 2x4, 8 PIN MILL-MAX 803-43-008-20-001000 9 4 JP1, JP2, JP3, JP4 HEADER, 3 PIN, 0.079" SINGLE ROW SAMTEC TMM-103-02-L-S 10 4 MTGS AT 4 CORNERS STAND-OFF, NYLON 0.5" KEYSTONE 8833 (SNAP-ON) 11 4 XJP1, XJP2, XJP3, XJP4 SHUNT, 0.079" CENTER SAMTEC 2SN-BK-G Hardware Rev 0 8 1 2 3 4 A B C C U2 D + + + E 710-DC1822B_REV01 HIGH CURRENT DUAL OUTPUT SYNCHRONOUS BUCK CONVERTER + E D Figure8. DC1822B Demo Circuit Schematic B A 1 2 3 4 DEMO MANUAL DC1822B SCHEMATIC DIAGRAM Rev 0 9 1 2 3 A B + C D D E 710-DC1822B_REV01 HIGH CURRENT DUAL OUTPUT SYNCHRONOUS BUCK CONVERTER E Figure9. DC1822B Demo Circuit Schematic + + 4 C + B + 10 + A 1 2 3 4 DEMO MANUAL DC1822B SCHEMATIC DIAGRAM Rev 0 1 2 3 4 A A B Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. C D D Figure10. DC1822B Demo Circuit Schematic C B E 710-DC1822B_REV01 HIGH CURRENT DUAL OUTPUT SYNCHRONOUS BUCK CONVERTER E 1 2 3 4 DEMO MANUAL DC1822B SCHEMATIC DIAGRAM Rev 0 11 DEMO MANUAL DC1822B ESD Caution ESD (electrostatic discharge) sensitive device. 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