DEMO MANUAL DC1822A
LTC3861EUHE
High Current, Dual Output
Synchronous Buck Converter
Description
Demonstration circuit 1822A is a dual output synchronous
buck converter featuring the LTC®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 × 6mm
DrMOS and a 13mm × 13mm iron powder type inductor.
An on-board 5V LT®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" × 1.2" area on the
top layer. The control circuit fits in a 1.1" × 1.0" area on
the bottom layer. The package style for the LTC3861EUHE
is a 36-lead 5mm × 6mm QFN.
L, LT, LTC, LTM, µModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other 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 at
http://www.linear.com/demo
(TA = 25°C), no airflow
CONDITION
Minimum Input Voltage
VALUE
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 Figures 2 and 3)
500kHz
VOUT1 = 1.5V, IOUT1 = 25A, VIN = 12V
91.6% Typical
VOUT2 = 1.2V, IOUT2 = 25A, VIN = 12V
90.7% Typical
dc1822af
1
DEMO MANUAL DC1822A
Quick Start Procedure
Demonstration circuit 1822A is easy to set up to evaluate
the performance of the LTC3861EUHE. Please refer to
Figure 1 for proper measurement equipment setup and
follow the procedure below.
1. With power off, connect the input supply, load and
meters, as shown in Figure 1. Preset the load to 0A
and VIN supply to be 0V. Place jumpers in the following
positions:
JP1 RUN1
ON
JP2 RUN2
ON
JP3
ON
INT BIAS
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
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.
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.
+
+
A
A
IOUT1
VOUT2
LOAD
–
IOUT2
Monitor voltage across COUT5
and COUT10 for accurate
efficiency measurements.
+
+
VOUT1
*
VOUT2
V
V
–
–
*
+
VIN
V
–
dc1822a F01
IIN
A
+
VIN SUPPLY
–
Figure 1. Proper Measurement Equipment Setup
dc1822af
2
DEMO MANUAL DC1822A
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 Figures 4 and 5 for transient
response curves with a 50% load change.
95
Efficiency (%)
90
85
Parameters and conditions:
RBOOST = 2.2Ω (R2, R25)
L = Würth 744355147
(0.47µH, DCR = 0.67mΩ ±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
dc1822a F02
Figure 2. Efficiency Curves for the 1.5V Rail of the DC1822A.
fSW = 500kHz with the FDMF6820A DrMOS
95
Efficiency (%)
90
85
Parameters and conditions:
RBOOST = 2.2Ω (R2, R25)
L = Würth 744355147
(0.47µH, DCR = 0.67mΩ ±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
dc1822a F03
Figure 3. Efficiency Curves for the 1.2V Rail of the DC1822A.
fSW = 500kHz with the FDMF6820A DrMOS
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3
DEMO MANUAL DC1822A
quick start procedure
88mV
1.5VO(AC)
50mV/DIV
25A
LOAD STEP
5A/DIV
12.5A
20µs/DIV
dc1822a F04
Figure 4. Load Step Response of the DC1822A 1.5V Rail at VIN = 12V.
COUT = 3× Sanyo 2R5TPE330M9 || 2× 100µF X5R 6.3V 1210, L = 0.47µH,
fSW = 500kHz
91mV
1.2VO(AC)
50mV/DIV
25A
LOAD STEP
5A/DIV
12.5A
20µs/DIV
dc1822a F05
Figure 5. Load Step Response of the DC1822A 1.2V Rail at VIN = 12V.
COUT = 3× Sanyo 2R5TPE330M9 || 2× 100µF X5R 6.3V 1210, L = 0.47µH,
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 Figure 8. To tie the
two outputs together, make the following modifications:
1. Stuff 0Ω 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 0Ω at R51 to disable
the error amplifier for phase 2. Also stuff 0Ω at R52.
• If VOUT2 is the master, then stuff 0Ω at R49 to disable
the error amplifier for phase 1. Also stuff 0Ω at R50.
3. Remove the 0Ω jumper at R13 and stuff a 100pF
capacitor at C14 for the IAVG signal.
4. Stuff 0Ω at R53, R48 and R54 to tie the COMP, TRK/SS
and RUN pins together.
5. Remove the redundant compensation components.
PARALLELING BOARDS
The DC1822A 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. Figure 6 shows how
to set up a 4-phase converter and Figure 7 shows how to
set up a 3-phase plus single phase converter.
dc1822af
4
Cu
VIN
VOUT
0.0mΩ
0.0mΩ
BOARD #1
BOARD #2
VOUT1 TO
VOUT2
R36 & R47
NS
NS
ILIM1 TO
VCC
R50
0Ω
0Ω
NS
NS
ILIM2 R
R24
0Ω
NS
FB1 TO
VCC
R49
0Ω
0Ω
FB2 TO
VCC
R51
0Ω
0Ω
TRK/SS1
TO
TRK/SS2
R48
0Ω
0Ω
COMP1
TO
COMP2
R53
0Ω
0Ω
RUN1 TO
RUN2
R54
Figure 6. 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 DC1822A
quick start procedure
dc1822af
5
6
VIN
Cu
VIN
VOUT1
NS
BOARD #2
NS
NS
ILIM1 TO
VCC
R50
STUFF
STUFF
ILIM1 R
R17
NS
0Ω
ILIM2 TO
VCC
R52
STUFF
NS
ILIM2 R
R24
0Ω
NS
FB1 TO
VCC
R49
NS
0Ω
FB2 TO
VCC
R51
NS
0Ω
TRK/SS1
TO
TRK/SS2
R48
NS
0Ω
COMP1
TO
COMP2
R53
NS
0Ω
RUN1 TO
RUN2
R54
0Ω
NS
NS
NS
PHASE MODE
SETTING
R41
R42
Single
phase
rail
VOUT2
Figure 7. Setup of a 3-Phase Plus Single Phase Converter; Phase 1 of Board 1 Is the Master of the 3-Phase Rail
0.0mΩ
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 DC1822A
quick start procedure
dc1822af
DEMO MANUAL DC1822A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
DC1822A Required Circuit Components
1
4
C1, C7, C8, C9
CAP, 0.22µF, 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, 10µF, 20%, 6.3V, X5R, 0805
AVX 08056D106MAT2A
5
4
C3, C11, C34, C35
CAP, 2.2µF, 10%, 16V, X7R, 0603
MURATA GRM188R61C225KE15D
6
2
C3-1, C3-2
CAP, 3300pF, 10%, 50V X7R, 0603
AVX 06035C332KAT2A
7
1
C6
CAP, 1µF, 20%, 25V, X5R, 0603
AVX 06033D105MAT2A
8
1
CIN2
CAP, 180µF, 20%, 16V, OSCON
SANYO 16SVP180MX
9
4
CIN3, CIN4, CIN5, CIN6
CAP, 22µF, 20%, 16V, X5R, 1210
AVX 1210YD226MAT2A
10
6
COUT1-COUT3, COUT6-COUT8
CAP, 330µF, 20%, 2.5V POSCAP 7343
SANYO 2R5TPE330M9
11
4
COUT4, COUT5, COUT9, COUT10
CAP, 100µF, 20%, 6.3V, X5R, 1210
AVX 12106D107MAT2A
12
2
L1,L2
IND, 0.47µH, 20%
WURTH 744355147
13
2
R1, R45
RES, 18.2k, 1%, 1/10W, 0603
VISHAY CRCW060318K2FKEA
14
4
R11, R18, R39, R43
RES, 10Ω, 1%, 1/10W, 0603
VISHAY CRCW060310R0FKEA
15
2
R17, R24
RES, 53.6k, 1%, 1/10W, 0603
VISHAY CRCW060353K6FKEA
16
2
R2, R25
RES, 2.2Ω, 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, 1Ω, 1%, 1/10W, 0603
YAGEO RC0603FR-071RL
21
2
R3-1, R3-2
RES, 280Ω, 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, 0Ω, 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
LINEAR TECH. LTC3861EUHE#PBF
28
2
U2, U3
MOSFET, DrMOS, DC-DC, 3.3V, PWM
FAIRCHILD FDMF6820A
Additional Circuit Components
1
1
C17
CAP, 0.22µF, 10%, 25V, X7R, 0603
AVX 06033C224KAT2A
2
1
C18
CAP, 1µF, 20%, 25V, X5R, 0603
AVX 06033D105MAT2A
3
1
C19
CAP, 22µF, 20%, 16V, X5R, 1210
AVX 1210YD226MAT2A
4
2
C2, C4, C5, C10, C12-C16, C20,
C22-C25, C27, C30-C33
CAP, 0603
OPT
5
1
C21
CAP, 22pF, 10%, 25V, NPO, 0603
AVX 06033A220KAT2A
6
1
C26
CAP, 1µF, 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
dc1822af
7
DEMO MANUAL DC1822A
parts list
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
11
0
D2, D3
CMDSH-3
OPT
12
1
L3
IND, 33µH, –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,
R33-R35, R41, R42, R47-R55, R62,
R64-R67, 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, 0.010Ω, 1%, 1W, 2010
IRC LRC-LRF2010LF-01-R010-F
21
1
R59
RES, 0Ω, 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
LINEAR TECHNOLOGY 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
Hardware
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, 2×4, 8 PIN
MILL-MAX 802-10-008-20-001000
8
1
J9
SOCKET, DBL ROW, RT ANGLE, 2×4, 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
dc1822af
8
1
2
3
4
A
B
C
C
U2
D
+
E
+
+
TECHNOLOGY
+
E
D
Figure 8. DC1822A Demo Circuit Schematic
B
A
1
2
3
4
DEMO MANUAL DC1822A
Schematic Diagram
dc1822af
9
1
2
3
A
B
+
C
D
D
E
TECHNOLOGY
E
Figure 9. DC1822A Demo Circuit Schematic
+ +
4
C
+
B
+
10
+
A
1
2
3
4
DEMO MANUAL DC1822A
Schematic Diagram
dc1822af
DEMO MANUAL DC1822A
Schematic Diagram
Figure 10. DC1822A Demo Circuit Schematic
dc1822af
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
DEMO MANUAL DC1822A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
dc1822af
12 Linear Technology Corporation
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