1
dc2285af
DEMO MANUAL
DC2285A
DESCRIPTION
LT8705A
80V VIN and VOUT Synchronous
4-Switch Buck-Boost DC/DC Controller
L, LT, LTC, LTM, Linear Technology , the Linear logo and Burst Mode are registered trademarks
of Analog Devices, Inc. All other trademarks are the property of their respectiveowners.
Demonstration circuit 2285A features two high power high
performance buck-boost LT
®
8705A converters operating
in master-slave configuration. The circuit can operate with
input voltages above, below or equal to the output voltage.
The demo board input range is 36V to 75V. The output is
optimized for 48V at 18A, with the output current limit set
at 20A. The circuit will operate with lower input voltage
than 36V if load current is reduced.
The LT8705A controller has integrated input current, input
voltage, output current and output voltage regulators. The
one regulator that wants to decrease current gets control
over the compensation pin V
C
. The inductor current is
controlled by the VC signal that is fed into a current com-
parator together with a ramp compensation signal.
While the current mode control limits the inductor
bothinnormal and in reverse direction, these current
limits have some variation as input voltage changes. The
input and output current regulators offer more accurate
currentlimits.
The input voltage regulator is typically used in applica-
tions with solar panels or high impedance power sources,
and will reduce the current if input voltage drops below
the set point.
The operating mode of the controller is determined
through the MODE pin (jumper JP1) and can be set
to discontinuous mode, forced continuous mode and
BurstMode
®
operation.
The LT8705A is capable of bidirectional current flow when
operating in forced continuous operation. It is important
to know that additional circuitry is required for controlled
reverse current operation, and this additional circuitry can
be elaborate in high power applications where tight con-
trol of current amplitude is required.
The SYNC inputs are used to synchronize the two LT8705A
power stages with 180-degree phase shift. The DC2285A
demo board contains a multiphase clock.
The LT8705A has internal series regulators that provide
INTV
CC
voltage (6.3V Typ) from V
IN
or EXTV
CC
. Especially
in high power applications the internal dissipation of these
series regulators can be high. The DC2285A demo board
includes an LT8631 buck regulator that is configured for
7.8V. By connecting this low voltage to VIN and EXTVCC
the power dissipation is reduced. The auxiliary 7.8V can
also be used to power external circuitry.
The LT8705A data sheet gives a complete description of
the part, operation and application information. The data
sheet should be read in conjunction with this quick start
guide for demo circuit 2285A. The input voltage range of
the LT8705A itself is 2.8V (with external auxiliary voltage
> 6.4V) to 80V and the output range is 1.3V to 80V. The
DC2285A demo board has an optional signal interface
that makes it easy to add potentiometers and switches
(or a microcontroller) for accurate external control of the
power stages.
The LT8705AEUHF is assembled in a 38-lead (5mm ×
7mm) plastic QFN package with a thermal pad underneath
the chip. Proper board layout is essential for maximum
thermal and electrical performance. The DC2285A circuit
board has mounting holes for an optional heat sink and
NTC resistor for monitoring heat sink temperature.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2285A
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dc2285af
DEMO MANUAL
DC2285A
PERFORMANCE SUMMARY
Specifications are at TA = 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Supply Range 36 75 V
VOUT Output Voltage 48 V
IOUT Maximum Output Current (Current limited at 20A) 20 A
FSW Switching Frequency 120 kHz
EFF Efficiency VIN = 36V IOUT = 18A (Set FBIN to 3.3V)
VIN = 48V IOUT = 18A
VIN = 60V IOUT =18A
VIN = 75V IOUT = 18A (Disable OVP at 74.6V)
98.6
98.7
99.0
98.7
%
%
%
%
INPUT VOLTAGE (A)
35
40
45
50
55
60
65
70
75
96
97
98
99
100
0
2
4
6
8
10
12
14
16
EFFICIENCY (%)
DISSIPATION (W)
dc2285A F01
EFFICIENCY
DISSIPATION
Figure 1. Efficiency and Dissipation at 18A Load
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dc2285af
DEMO MANUAL
DC2285A
QUICK START PROCEDURE
1. Demonstration circuit 2285A is easy to set up to evalu-
ate the performance of the LT8705A. Refer to Figure2
for proper measurement equipment setup and follow
the procedure below. Make sure the configuration
jumpers are set correctly.
2. With power off, connect the input power supply to
VIN(J3) and GND (J4).
3. Connect the SHUTDOWN pin (J7:10) to VAUX (J7:12)
to disable the board.
4. Apply 48V to the input. The power source must have
greater than 38A capability if you want to evaluate the
board with full load over the input range.
5. Open the connection from SHUTDOWN to VAUX to
enable the board.
6. Note that the demo circuit will operate at VIN down to
32V, as set by the FB
IN
loop. If operation at this low
input voltage is not preferred, increase the value of R67.
7. Once the proper output voltage is established, adjust
the load and the input voltage within the operating
range and observe the output voltage regulation, effi-
ciency and other parameters as needed. When measur-
ing input/output voltages, measure at the input/output
terminals of the board to avoid measurement error
caused by voltage drops in cables.
8. To measure input/output voltage ripple, avoid a long
ground lead on the oscilloscope probe. A commonly
accepted method is to remove the oscilloscope probe
end cap and ground lead and set the 20MHz bandwidth
limit on the oscilloscope. Measure the input/output
voltage ripple by touching the probe tip directly to the
positive terminal of the input or output capacitor. Con-
nect the probe ground terminal to the board’s GND
plane near the capacitor with a very short wire.
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dc2285af
DEMO MANUAL
DC2285A
Figure 2. Proper Measurement Equipment Setup
LOAD
+
–
+
–
+
–
CLOSE TO SHUT OFF POWER
OPEN SWITCH TO RUN
USE VERY SHORT AND
HEAVY GAUGE WIRE
+
–
QUICK START PROCEDURE
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dc2285af
DEMO MANUAL
DC2285A
PARTS LIST
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
Required Circuit Components
1 3 CIN4, CIN5, CIN6 CAP., ALUM., 33μF, 80V, 20% PANASONIC, EEHZA1K330P
2 3 COUT1, COUT2, COUT3 CAP., ALUM., 56μF, 63V, 20% SUN ELEC., 63HVH56M
3 3 C1, C53, C56 CAP., CER., 10000pF, X7R, 25V, 10%, 0603 MURATA, GRM188R71E103KA01D
4 4 C2, C3, C25, C26 CAP., CER., 0.22μF, X7R, 16V, 10%, 0603 TDK, C1608X7R1C224K080AC
5 2 C4, C27 CAP., CER., 0.1μF, X7R, 16V, 10%, 0603 MURATA, GRM188R71C104KA01D
6 1 C5 CAP., CER., 0.47μF, X7R, 16V, 10%, 0603 MURATA, GRM188R71C474KA88D
7 4 C6, C7, C28, C29 CAP., CER., 1μF, X7R, 16V, 10%, 0805 MURATA, GRM21BR71C105KA01L
8 8 C8, C9, C10, C11, C30-C33 CAP., CER., 10μF, X7S, 100V, 20%, 2220 TDK, CKG57KX7S2A106M335JH
9 4 C12, C13, C34, C35 CAP., CER., 1000pF, X7R, 25V, 10%, 0603 MURATA, GRM188R71E102KA01D
10 2 C14, C36 CAP., CER., 1μF, X7R, 16V, 10%, 0603 MURATA, GRM188R71C105KA12D
11 1 C15 CAP., CER., 6800pF, X7R, 25V, 10%, 0603 MURATA, GRM188R71E682KA01D
12 2 C16, C38 CAP., CER., 220pF, NP0, 25V, 10%, 0603 AVX, 06033A221KAT2A
13 6 C19, C20, C21, C40, C41, C42 CAP., CER., 4.7μF, X5R, 16V, 10%, 0603 TDK, C1608X5R1C475K080AC
14 1 C37 CAP., CER., 4700pF, NP0, 50V, 5%, 0603 MURATA, GRM1885C1H472JA01D
15 4 D1, D2, D3, D4 DIODE, 200V, 1A, SOD123F CENTRAL SEMI., CMMR1U-02
16 2 L1, L2 IND., PWR., HIGH CURRENT, 15μH, ±10% COILCRAFT, SER2918H-153KL
17 4 M1, M4, M7, M8 XSTR., MOSFET, N-CH, 80V, 100A, PG-TDSON-8 INFINEON, BSC040N08NS5
18 4 M2, M3, M9, M10 XSTR., MOSFET, N-CH, 80V, PG-TDSON-8 INFINEON, BSC117N08NS5
19 1 RSNS1 RES, CHIP, SENSE, 0.003Ω, 3W, 1%, WIDE 2512 SUSUMU, KRL6432E-M-R003-F-T1
20 2 RSNS2, RSNS4 RES, CHIP, SENSE, 0.004Ω, 3W, 1%, WIDE 2512 SUSUMU, KRL6432E-M-R004-F-T1
21 2 RSNS3, RSNS5 RES, CHIP, SENSE, 0.006Ω, 3W, 1%, WIDE 2512 SUSUMU, KRL6432E-M-R006-F-T1
22 8 R1-R4, R30-R33 RES, CHIP, 1Ω, 1/10W, 1%, 0603 VISHAY, CRCW06031R00FKEA
23 2 R8, R37 RES, CHIP, 3.3Ω, 1/10W, 1%, 0603 VISHAY, CRCW06033R30FKEA
24 4 R9, R10, R38, R39 RES, CHIP, 10Ω, 1/10W, 1%, 0603 VISHAY, CRCW060310R0FKEA
25 2 R11, R40 RES, CHIP, 22.1Ω, 1/10W, 1%, 0603 VISHAY, CRCW060322R1FKEA
26 1 R12 RES, CHIP, 49.9Ω, 1/10W, 1%, 0603 VISHAY, CRCW060349R9FKEA
27 1 R16 RES, CHIP, 100k, 1/10W, 1%, 0603 VISHAY, CRCW0603100KFKEA
28 1 R65 RES, CHIP, 10k, 1/10W, 1%, 0603 VISHAY, CRCW060310K0FKEA
29 1 R21 RES, CHIP, 23.7k, 1/10W, 1%, 0603 VISHAY, CRCW060323K7FKEA
30 2 R22, R43 RES, CHIP, 365k, 1/10W, 1%, 0603 VISHAY, CRCW0603365KFKEA
31 1 R23 RES, CHIP, 20k, 1/10W, 1%, 0603 VISHAY, CRCW060320K0FKEA
32 1 R26 RES, CHIP, 750k, 1/10W, 1%, 0603 VISHAY, CRCW0603750KFKEA
33 1 R42 RES, CHIP, 12.1k, 1/10W, 1%, 0603 VISHAY, CRCW060312K1FKEA
34 1 R45 RES, CHIP, 590k, 1/10W, 1%, 0603 VISHAY, CRCW0603590KFKEA
35 1 R44 RES, CHIP, 16.9k, 1/10W, 1%, 0603 VISHAY, CRCW060316K9FKEA
36 1 R73 RES, CHIP, 34.8k, 1/10W, 1%, 0603 VISHAY, CRCW060334K8FKEA
37 1 R75 RES, CHIP, 36.5k, 1/10W, 1%, 0603 VISHAY, CRCW060336K5FKEA
38 2 R79, R80 RES, CHIP, 38.3k, 1/10W, 1%, 0603 VISHAY, CRCW060338K3FKEA
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dc2285af
DEMO MANUAL
DC2285A
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
39 1 R81 RES, CHIP, 48.7k, 1/10W, 1%, 0603 VISHAY, CRCW060348K7FKEA
40 1 R82 RES, CHIP, 60.4k, 1/10W, 1%, 0603 VISHAY, CRCW060360K4FKEA
41 2 U1, U2 I.C., BUCK BOOST DC/DC CONTROLLER, 38-QFN LINEAR TECH., LT8705AEUHF#PBF
42 1 U4 I.C., OP AMP, SO14 LINEAR TECH., LTC2052CS#PBF
Additional Demo Board Circuit Components
1 7 C1, C55, C57, C58, C59, C60, C61 CAP., CER., 10000pF, X7R, 25V, 10%, 0603 MURATA, GRM188R71E103KA01D
2 1 C46 CAP., CER., 0.1μF, X7R, 16V, 10%, 0603 MURATA, GRM188R71C104KA01D
3 1 C47 CAP., CER., 1μF, X7R, 16V, 10%, 0603 MURATA, GRM188R71C105KA12D
4 3 C17, C18, C39 CAP., CER., 22pF, NP0, 25V, 5%, 0603 AVX, 06033A220JAT2A
5 1 C45 CAP., CER., 0.1μF, X7R, 10V, 10%, 0402 MURATA, GRM155R71A104KA01D
6 1 C48 CAP., CER., 1μF, X7R, 100V, 10%, 1210 AVX, 12101C105KAT2A
7 1 C49 CAP., CER., 2.2μF, X5R, 10V, 10%, 0402 MURATA, GRM155R61A225KE95D
8 1 C50 CAP., ALUM., 22μF, 100V, 20% SUNCON, 100CE22BS
9 1 C51 CAP., CER., 4.7pF, NP0, 50V, ±0.25pF, 0603 MURATA, GRM1885C1H4R7CA01D
10 1 C52 CAP., CER., 47μF, X5R, 10V, 10%, 1210 MURATA, GRM32ER61A476KE20K
11 2 D5, D6 DIODE, SCHOTTKY, 100V, POWERDI123 DIODES INC., DFLS1100-7
12 5 D9, D10, D11, D12, D13 DIODE, 75V, 150mA, SOD-323 VISHAY, 1N4148WS-E3-08
13 1 JP1 HEADER 4-PIN 0.079 SINGLE ROW WURTH ELEKTRONIK, 62000411121
14 4 JP2, JP3, JP4, JP5 HEADER 3-PIN 0.079 SINGLE ROW WURTH ELEKTRONIK, 62000311121
15 4 XJP1, XJP2, XJP3, XJP4 SHUNT, 2mm WURTH ELEKTRONIK, 60800213421
16 0 J1, J2 (OPT) RIGHT ANGLE CONTACT, 45A ANDERSON POWER, 1336G1
17 0 J1, J2 (OPT) HOUSING, +PIN, RED ANDERSON POWER, 1327-BK
18 0 J1, J2 (OPT) HOUSING, –PIN, BLACK ANDERSON POWER, 1327G6-BK
19 0 J1, J2 (OPT) STAPLES FOR PCB ASSY. ANDERSON POWER, 114555P2
20 1 J7 HEADER 13-PIN 0.100 DOUBLE ROW WURTH ELEKTRONIK, 61302621121
21 1 J8 HEADER 4-PIN 0.100 SINGLE ROW WURTH ELEKTRONIK, 61300411121
22 1 J9 HEADER 3-PIN 0.100 SINGLE ROW WURTH ELEKTRONIK, 61300311121
23 1 J10 HEADER 4-PIN 0.100 DOUBLE ROW WURTH ELEKTRONIK, 61300821121
24 0 J11 (OPT) HEADER 4-PIN , OPTION
25 1 L3 IND., PWR., 22μH VISHAY, IHLP2525CZER220M11
26 0 M5, M6, M11, M12 (OPT) XSTR., MOSFET, OPTION, PG-TDSON-8
27 1 Q1 TRANS, NPN, 40V, 0.6A, SOT-23 FAIRCHILD SEMI., MMBT3904
28 2 Q2, Q3 TRANS, PNP, 40V, 0.2A , SOT-23 FAIRCHILD SEMI., MMBT3906
29 1 Q4 XSTR., MOSFET, N-CH, 60V, 150MA, SOT-23 DIODES INC., BS170FTA
30 1 RT1 THERMISTOR, 10k, NTC, 0603 MURATA, NCU18XH103J6SRB
31 5 R5, R6, R7, R35, R36 RES, CHIP, 1Ω, 1/10W, 1%, 0603 VISHAY, CRCW06031R00FKEA
32 8 R13, R14, R15, R41, R89, R90, R92, R93 RES, CHIP, 100k, 1/10W, 1%, 0603 VISHAY, CRCW0603100KFKEA
PARTS LIST
7
dc2285af
DEMO MANUAL
DC2285A
ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER
33 0 R17, R27, R48, R53, R69, R100, R103,
R104, R106-R113, R118 (OPT)
RES., OPTION, 0603
34 10 R18, R56, R57, R59, R60, R91,
R115, R116, R117
RES, CHIP, 10k, 1/10W, 1%, 0603 VISHAY, CRCW060310K0FKEA
35 5 R19, R55, R64, R66, R67 RES, CHIP, 1k, 1/10W, 1%, 0603 VISHAY, CRCW06031K00FKEA
36 1 R77 RES, CHIP, 365k, 1/10W, 1%, 0603 VISHAY, CRCW0603365KFKEA
37 1 R24 RES, CHIP, 46.4k, 1/10W, 1%, 0603 VISHAY, CRCW060346K4FKEA
38 1 R25 RES, CHIP, 47.5k, 1/10W, 1%, 0603 VISHAY, CRCW060347K5FKEA
39 1 R49 RES, CHIP, 115k, 1/10W, 1%, 0603 VISHAY, CRCW0603115KFKEA
40 5 R50, R51, R68, R70, R101 RES, CHIP, 1M, 1/10W, 1%, 0603 VISHAY, CRCW06031M00FKEA
41 1 R52 RES, CHIP, 25.5k, 1/10W, 1%, 0603 VISHAY, CRCW060325K5FKEA
42 1 R58 RES, CHIP, 34.8k, 1/10W, 1%, 0603 VISHAY, CRCW060334K8FKEA
43 1 R61 RES, CHIP, 150k, 1/10W, 1%, 0603 VISHAY, CRCW0603150KFKEA
44 2 R62, R63 RES, CHIP, 14.7k, 1/10W, 1%, 0603 VISHAY, CRCW060314K7FKEA
45 1 R72 RES, CHIP, 412k, 1/10W, 1%, 0603 VISHAY, CRCW0603412KFKEA
46 2 R74, R76 RES, CHIP, 36.5k, 1/10W, 1%, 0603 VISHAY, CRCW060336K5FKEA
47 1 R78 RES, CHIP, 38.3k, 1/10W, 1%, 0603 VISHAY, CRCW060338K3FKEA
48 1 R83 RES, CHIP, 576k, 1/10W, 1%, 0603 VISHAY, CRCW0603576KFKEA
49 2 R84, R85 RES, CHIP, 51.1k, 1/10W, 1%, 0603 VISHAY, CRCW060351K1FKEA
50 1 R86 RES, CHIP, 75k, 1/10W, 1%, 0603 VISHAY, CRCW060375K0FKEA
51 1 R88 RES, CHIP, 30.1k, 1/10W, 1%, 0603 VISHAY, CRCW060330K1FKEA
52 1 R102 RES, CHIP, 383k, 1/10W, 1%, 0603 VISHAY, CRCW0603383KFKEA
53 2 R54, R105, R119 RES, CHIP, 0Ω, 1/10W, 1%, 0603 VISHAY, CRCW06030000Z0EA
54 1 R114 RES, CHIP, 422k, 1/10W, 1%, 0603 VISHAY, CRCW0603422KFKEA
55 1 U3 I.C. REGULATOR, 20-TSSOP LINEAR TECH., LT8631EFE#PBF
56 1 U5 I.C., OP AMP, SO14 LINEAR TECH., LTC2052CS#PBF
Hardware: For Demo Board Only
1 4 J3, J4, J5, J6 STUD, TEST PIN PEM, KFH-032-10ET
2 8 J3, J4, J5, J6 NUT, BRASS NUTS # 10-32 ANY, 10-32M/S BR PL
3 8 J3, J4, J5, J6 RING, LUG RING # 10 KEYSTONE, 8208
4 4 J3, J4, J5, J6 WASHER, TIN PLATED BRASS ANY, #10EXT- BZ TN
5 4 MH1-MH4 STAND-OFF, NYLON 0.375" WURTH ELEKTRONIK, 702933000
6 1 PCB, DC2285A DEMO CIRCUIT 2285A
7 2 STENCIL, DC2285A (TOP & BOTTOM) STENCIL DC2285A
PARTS LIST
8
dc2285af
DEMO MANUAL
DC2285A
SCHEMATIC DIAGRAM
DCM
FCM
BURST
MODE
SHAREBUS
MASTER
SLAVE
LOADSHARE
CONNECTOR
CONTROL
INTERFACE
MEGACAPS
CKG57KX7S2A106M335JH
OPTIONAL LT8490 INTERFACE
EXT CLOCK INPUT
INT
EXT
INT
EXT
INT
EXT
INT
EXT
(80V) (80V)
VOUT
VIN
VIN
LDO33
LDO33
LDO33
LDO33
VIN LDO33 LDO33
LDO33
LDO33
LDO33
VCC_INT
VCC_INT
SYNC
VAUX
SHUTDOWN
VOUTSNS
CLKOUT2
IMONOUT2
MODE
SWEN2
SHDN1
VAUX
SWEN
CLKOUT
SYNC2
SYNC3
SYNC
R113
OPT
D121N4148WS
1 2
R14
100K
R5
1
R17
OPT
L1
15uH
SER2918H-153KL
C58
0.01uF
R91
10k
R12
49.9
R66
1K
R4
1
R82
57.6K
C17
22pF
R81
48.7K
R63
14.7K
-
+
U4C
LTC2052CS
9
10
8
R69
1M
R61
150K
R83
576K
C1
0.01uF
R76
36.5K
R117
10K
R89
100K
R109
OPT
R16
100K
R103
OPT
C14
1uF
M5
OPT
4
5 3
6 2
17
8
-
+
V+
V-
U5A
LTC2052CS
2
3
1
411
C61
0.01uF
R57
10K
R9
10
C11
10uF
100V
CKG57K
Q1
MMBT3904
1
32
R85
51.1K
R104
OPT
R55
1K
R84
51.1K
C59
0.01uF
Q4
BS170F/SOT
1
3 2
R74
36.5K
R21
23.7K
JP3
2
1
3
C15
6.8nF
NP0
C54
0.01uF
RSNS3
0.006
1225 Wide
J8
1 2
3
5 6
4
7 8
R15
100K
R56
10K
J7
1 2
3
5 6
4
7 8
109
11
13
15
17
19
12
14
16
18
20
22
24
26
21
23
25
R101
1M
R116
10K
Q2
MMBT3906/SOT
1
2 3
C57
0.01uF
R19
1K
R11
22.1
C19
4.7uF
C62
0.1uF
R59
10K
R78
38.3K
D11 1N4148WS
12
R18
10K
C3
0.22uF
R10
10
-
+
V+
V-
U4A
LTC2052CS
2
3
1
411
R2
1
R22
365K
M2
BSC117N08NS5
4
53 62
1 7
8
C16
220pF
NP0
C13
1nF
R111
OPT
R65
10K
C6
1.0uF
0805
RSNS1
0.003
1225
1W 1%
C10
10uF
100V
CKG57K
R80
38.3k
-
+
U5C
LTC2052CS
9
10
8
RSNS2
0.004
1225
1W 1%
M1
BSC040N08NS5
4
5 3
6 2
17
8
C18
22pF
D13
1N4148WS
1 2
R64
1K
C53
0.01uF
J12
2
1
3
J11
OPT
1
2
3
4
C7
1.0uF
0805
R115
10K
R100
OPT
R58
34.8K
M3
BSC117N08NS5
4
53 62
1 7
8
R60
10K
R27
OPT
D10 1N4148WS
12
R25
47.5K
R86
34.8k
C2
0.22uF
R23
20K
R75
36.5K
D9
1N4148WS
12
R105
0
-
+
U5B
LTC2052CS
6
5
7
-
+
U4B
LTC2052CS
6
5
7
R8
3.3
R68
1M
JP5
2
1
3
C60
0.01uF
R77
365K
R24
46.4K
-
+
U4D
LTC2052CS
12
13
14
R13
100K
M4
BSC040N08NS5
4
53 62
1 7
8
R72
412K
Q3
MMBT3906/SOT
1
2 3
J9
1 3
2
C8
10uF
100V
CKG57K
JP2
2
1
3
T
RT1
10K NTC
C63
0.1uF
C9
10uF
100V
CKG57K
R3
1
R114
422K
JP4
2
1
3
R26
750K
R102
383K
R1
1
C12
1nF
R106
OPT
R79
38.3k
R67
1K
C4
0.1uF
D2
CMMR1U-02
21
JP1
1
2
3
4
C56
0.01uF
R120
221K
R108
OPT
C21
4.7uF
M6
OPT
4
53 62
1 7
8
R62
14.7K
J10
1 2
3
5 6
4
7 8
C20
4.7uF
R118
100K
R90
100K
C5
0.47uF
D1
CMMR1U-02
21
C55
0.01uF
R88
30.1k
R110
OPT
U1
LT8705AEUHF
INTVCC
35
MODE
37
IMONIN
38
#SHDN
1
CSN 2
CSP 3
LDO33
4
FBIN
5FBOUT 6
IMONOUT
7
RT
12
BG2 16
GATEVCC
15
BG1 14
BOOST2 17
TG2 18
SW2 19
SW1 21
TG1 22
BOOST1 23
EXTVCC
29
CSNOUT 30
CSPOUT 31
CSNIN
32
CSPIN
33
AGND
13
VIN
34
39
PGND
SYNC
11
VC
8
SS
9
CLKOUT 10
N/C 20
N/C 24
SRVO_FBOUT 28
SRVO_FBIN 25
SRVO_IIN 26
SRVO_IOUT 27
SWEN 36
R70
1M
R6
1
R119
0
R112
OPT
R73
34.8K
-
+
U5D
LTC2052CS
12
13
14
R107
OPT
R7
1
+
+
LTC6909CMS
U6
V A
1
GND
2
PH0
3
PH1
4
OUT1
5
OUT2
6
OUT3
7
OUT4
8OUT5 9
OUT6 10
OUT7 11
OUT8 12
V D 13
MOD 14
PH2 15
SET 16
CSNOUT
FBOUT
LDO33
IMONIN
CSNIN
IMONOUT
SHDN1
CSPOUT
LDO33
VAUX
VINADJ
IINADJ
IOUTADJ
VOUTADJ
VINADJ
IMONOUT
IINADJ
CLKOUT
SHARE
VOUTADJ
FBIN
IOW
IOUTADJ
IMONIN
IMONOUT
FBOUT
IMONOUT
IOUTADJ
ICTRL2
IMONOUT2
VC
IMONIN
SWEN
SHUTDOWN
MODE VAUX
GND GND
TEMP
TEMP
MODE
LDO33
GND
CLKOUT3
IMONOUT3
SWEN
SWEN2 SHDN1
FBIN
SWEN
SWEN2
VIN VOUT
PH1
PH3
PH5
PH7
PH2
PH4
PH6
PH8
CLKOUT3
SYNC3
PH2
PH3
PH4 PH5
PH6
PH7
PH8
PH1
PH1
LDO33
ICTRL2 ICTRL
ICTRL
IOWIMONOUT3
9
dc2285af
DEMO MANUAL
DC2285A
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
SCHEMATIC DIAGRAM
MEGACAPS
CKG57KX7S2A106M335JH
+
-
VIN
MAX 75V
+
-
VOUT
48V / 20A
OVP = 60.1V
(400kHz)
IHLP2525CZER220M11
7.8V 0.25A
(1A peak)
VOUT
VIN
VIN
VOUT
VINVOUT
LDO33
VCC_INT2
VCC_INT2
SYNC2
VAUX
LDO33_2
VOUTSNS
CLKOUT2
IMONOUT2
MODE
SWEN2
SHDN1
SWEN
SWEN2
R54
0
R38
10
R30
1
J1
OPT
2
1
C45
0.1uF
0402
10V
C41
4.7uF
C26
0.22uF
M9
BSC117N08NS5
4
53 62
1 7
8
R31
1
R93
100K
J4
GND
R52
25.5K
R49
115K
1%
R42
12.1K
U2
LT8705AEUHF
INTVCC
35
MODE
37
IMONIN
38
#SHDN
1
CSN 2
CSP 3
LDO33
4
FBIN
5FBOUT 6
IMONOUT
7
RT
12
BG2 16
GATEVCC
15
BG1 14
BOOST2 17
TG2 18
SW2 19
SW1 21
TG1 22
BOOST1 23
EXTVCC
29
CSNOUT 30
CSPOUT 31
CSNIN
32
CSPIN
33
AGND
13
VIN
34
39
PGND
SYNC
11
VC
8
SS
9
CLKOUT 10
N/C 20
N/C 24
SRVO_FBOUT 28
SRVO_FBIN 25
SRVO_IIN 26
SRVO_IOUT 27
SWEN 36
D6
DFLS1100
21
C39
22pF
R33
1
M11
OPT
4
5 3
6 2
17
8
C52
47uF
10V
1210
M12
OPT
4
53 62
1 7
8
R32
1
R36
1
M8
BSC040N08NS5
4
53 62
1 7
8
D3
CMMR1U-02
21
C27
0.1uF
C28
1.0uF
0805
R39
10
C38
220pF
NP0
L2
15uH
SER2918H-153KL
+
C50
22uF
100CE22BS
100V
M7
BSC040N08NS5
4
5 3
6 2
17
8
R51
1M
C49
0402
2.2uF
10V
C35
1nF
+
CIN4
33uF
80V
EEHZA1K330P
C29
1.0uF
0805
J5
RSNS4
0.004
1225
1W 1%
R92
100K
R50
1M
1%
R48
OPT
J3
C32
10uF
100V
CKG57K
U3
LT8631EFE
INTVCC 16
VIN
1
NC 13
SYNC/MODE
7
BST 18
FB 11
IND 14
GND
21
RT
8
NC
9
NC 15
SW 20
PG
5
VOUT 12
EN/UV
3
NC
6
TR/SS
10
C51
4.7pF
J2
OPT
2
1
C37
4.7nF
NP0
C33
10uF
100V
CKG57K
R44
16.9K
C30
10uF
100V
CKG57K
C48
1uF
100V
1210
+
COUT2
56uF
63V
63HVH56M
D5
DFLS1100
21
+
COUT3
56uF
63V
63HVH56M
C34
1nF
D4
CMMR1U-02
21
R35
1
+
CIN6
33uF
80V
C47
1uF
10V
R40
22.1
C25
0.22uF
RSNS5
0.006
1225 Wide
C36
1uF
J6 GND
R37
3.3
C46
0.1uF
R43
365K
C40
4.7uF
+
CIN5
33uF
80V
R41
100K
M10
BSC117N08NS5
4
53 62
1 7
8
R53
OPT
L3
22uH
R45
590K
C42
4.7uF
+
COUT1
56uF
63V
63HVH56M
C31
10uF
100V
CKG57K
CSNOUT2
FBOUT2
CSPOUT2
VAUX
LDO33_2
VAUX
10
dc2285af
DEMO MANUAL
DC2285A
LINEAR TECHNOLOGY CORPORATION 2017
LT 0817 • PRINTED IN USA
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