DC888A-C - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
LTC3725/LTC3706
DESCRIPTION
Demonstration circuit 888A-C is a high power isolated synchronous forward converter featuring the
LTC3725 and LTC3706. When powered from a 3672V input, a single DC888A-C provides an isolated
12V at 20A in a quarter-brick footprint. If higher output current is required, multiple DC888A boards may
be stacked together using on-board connectors for a
complete PolyPhase current sharing solution. The
converter operates at 250kHz and achieves efficiency
up to 94.2% with synchronous output rectifiers.
Secondary-side control eliminates complex optocou-
pler feedback, providing fast transient response with
a minimum amount of output capacitance. Additional
DC888A versions include DC888A-A (3.3V at 50A)
and DC888A-B (5V at 40A). The simple architecture
can be easily modified to meet different input and
output voltage requirements.
Design files for this circuit board are available.
Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
36V
Maximum Input Voltage
72V
Output Voltage VOUT
VIN = 36V to 72V, IOUT = 0A to 20A
12V
Maximum Output Current
200LFM
20A
Typical Output Ripple VOUT
VIN = 48V, IOUT = 20A, 250kHz
< 150mVP–P
Output Regulation
Over All Input Voltages and Output Currents
±1% (Reference)
Peak Deviation with 10A to 20A Load Step (10A/us)
±750mV
Settling Time
•50us
Load Transient Response
Nominal Switching Frequency
250kHz
Efficiency
VIN = 36V, IOUT = 12A
94.2% Typical
Isolation
BASIC
1500VDC
Size
Component Area x Top x Bottom Component Height
2.3” x 1.45” x 0.4” x 0.075”
OPERATING PRINCIPLES – SINGLE PHASE
The LTC3706 secondary side controller is used on the
secondary and the LTC3725 smart driver with selfstarting capability is used on the primary. When an
input voltage is applied, the LTC3725 (U1 in Figure
15), which is powered through R29 and Q28, begins
a controlled soft-start of the output voltage by switching MOSFETs Q9 and Q11. As the output voltage begins to rise, the LTC3706 secondary controller is
quickly powered up via D24, Q29, C67, and Q27. The
LTC3706 then assumes control of the output voltage
by sending encoded PWM gate pulses to the
LTC3725 primary driver via signal transformer, T2.
The LTC3725 then operates as a simple driver receiving both input signals and bias power through T2.
The transition from primary to secondary control occurs seamlessly at a fraction of the output voltage.
From that point on, operation and design simplifies to
that of a simple buck converter. The LTC3706 regu-
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
lates by observing the output voltage directly resulting in superior output voltage regulation and transient
response.
OPERATING PRINCIPLES – POLYPHASE
The LTC3725 and LTC3706 allow the user to develop
modular power supply “building blocks” that can be
added as power/current requirements increase. Connecting two DC888A power supplies in a PolyPhase
configuration has several advantages. By distributing
power across multiple high power/current supplies,
heat is also distributed, reducing individual component temperatures. Each parallel module develops
equal output currents so that electrical and thermal
stresses are shared, increasing reliability. Multi-phase
operation and Shared input and output filtering result
in fewer/smaller input/output capacitors and inductors for a given voltage/current ripple or transient response.
In PolyPhase systems, one power supply is configured as a “master” and one as a “slave”. The master
communicates switching frequency via the PT+ pin to
FS/SYNC pin of the slave (Figures 19 and 20). The
relative clock phase of each stage is determined by
the slave. The master’s voltage error amplifier’s output (ITH pin) controls the output current of all the
phases via the ITH pin voltage which is distributed to
each slave’s unity-gain differential amplifier.
Several of the signals that are shared between the
master and the slave are of a bidirectional nature. A
fault on either phase can be communicated to the opposite phase via the primary side SS/FLT pin interconnection or the secondary side RUN/SS interconnection. Sharing Vcc on the secondary side ensures
the master, which initially develops this bias voltage,
and slave power up simultaneously. Each phase then
contributes to the shared Vcc bus. Finally, the input
voltage (Vin) and output voltage (Vout) busses are
interconnected to allow for load sharing.
OPTIONAL POLYPHASE SETUP
Only minor modifications and minimal interconnections are needed to implement PolyPhase with the
DC888. See component changes list (Figure 18) and
schematics (Figures 21 and 22) for the required electrical changes to master and slave units. After the
modifications are done, the boards are then stacked
one on top of another (Figure 23). J1 and P1 headers
interconnect small signals and E1, E2, E3, and E4
stand offs provide interconnection for the power signals.
The DC888 was designed primarily to demonstrate
the chipset’s single phase operation and therefore be
further optimized for PolyPhase applications. A small
resistor can be placed between the R76/D27 junction
and C70/U2-16 junction to reduce already small PWM
jitter associated with separate master and slave
ground planes. Another optimization can result from
combining each individual phase’s input/output filter
components into one shared input/output filter.
QUICK START PROCEDURE
Demonstration Circuit 888A-C is easy to set up to
evaluate the performance of the LTC3725 and
LTC3706. Refer to Figure 1 for proper equipment
setup. Follow the procedure below:
NOTE: When
measuring the input or output voltage
ripple, care must be taken to avoid a long ground lead
on the scope probe. Measure the output (or input)
voltage ripple by touching the probe tip and probe
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
in order to measure the DC888A-C’s input current.
ground directly across the +Vout and –Vout (or +Vin
and –Vin) terminals. See 0 for proper scope probe
technique.
1.
The optional input LC filter stage (C2/L5) lowers ac
input rms current. A power supply’s complete input filter must have output impedance that is less
than the converter input impedance to assure stability. This may require a damping impedance. (See
Linear Technology Application Note AN19 for a
discussion of input filter stability.) A source with a
50mOhm or higher ESR at the filter resonant frequency is one way of providing damping for the filter elements provided on the DC888A. For bench
testing, adding an 82uF electrolytic capacitor such
as a Sanyo 100MV82AX to the input terminals will
provide suitable damping and ripple current capability. The values selected have a filter resonant
frequency that is below the converter switching
frequency, thus avoiding high circulating currents
in the filter.
2.
Set an input power supply to a voltage of 36V.
Make sure that it is capable of 36V to 72V at a current supplying capability of at least 8A per number
of phases being tested. Then, turn off the supply.
3.
With power off, connect the supply to the input
terminals +Vin and –Vin.
a.
b.
Input voltages lower than 36V can keep the converter from turning on due to the undervoltage
lockout feature of the LTC3725.
If efficiency measurements are desired, an ammeter capable of measuring at least 8Adc per
phase can be put in series with the input supply
c.
4.
A voltmeter with a capability of measuring • 72V
can be placed across the input to get an accurate
input voltage measurement.
Turn on the power at the input.
NOTE: Make sure that
the input voltage • 72V.
5.
Check for the proper output voltage of 12V.
6.
Turn off the power at the input.
7.
Once the proper output voltages are established,
connect a variable load capable of sinking 20A per
phase at 12V to the output terminals +Vout and –
Vout. Set current to 0A.
8.
a.
If efficiency measurements are desired, an ammeter or a resistor current shunt that is capable
of handling at least 20Adc per phase can be put
in series with the output load in order to measure the DC888A-C’s output current.
b.
A voltmeter with a capability of measuring at
least 12V can be placed across the output terminals in order to get an accurate output voltage
measurement.
Turn on the power at the input.
NOTE: If
there is no output, disconnect the load to
verify that the load is not set too high.
9.
Once the proper output voltage is established, adjust the load within the operating range and observe the output voltage regulation, ripple voltage,
efficiency and other desired parameters.
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Measuring Input or Output Ripple
4
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
MEASURED DATA
Figures 3 through 14 are measured data for a typical DC888A-C. Figures 15 through 23 consist of schematics, bill of
materials, and a picture.
Figure 3. Efficiency
Figure 4. Output Voltage Ripple (36Vin/48Vin/72Vin, 20A, Single Phase)
5
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 5. Load Transient Response (48Vin, 10A to 20A to 10A at 10A/us, Single Phase)
Figure 6. Loop Response (48Vin, 20A, Single Phase)
6
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 7. Turn-on (48Vin, 20A, Single Phase)
Figure 8. Turn-on (36Vin, 40A, PolyPhase)
7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 9. Transient Sharing of Inductor Current (48Vin, 20A to 40A, PolyPhase)
Figure 10. Transient Sharing of Inductor Current (48Vin, 40A to 20A, PolyPhase)
8
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 11. Temp Data (48Vin, 20A, 200LFM airflow – top)
Figure 12. Temp Data (48Vin, 20A, 200LFM airflow – bottom)
9
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 13. Temp Data (48Vin, 18A, 0LFM airflow – top)
Figure 14. Temp Data (48Vin, 18A, 0LFM airflow – bottom)
10
B
A
T4
3
1
DA2318-ALC
6
4
D
C
D1
IS+
C29
10nF
SSFLT
U1
3
7.5
R76
330
R84
4
-VOUT
C85
0.1uF
Q29
Si2303BDS
Vaux
FS/IN-
FB/IN+
LTC3725EMSE
R79
68K
D2
CMPSH1-4
100uH
L1
R29
100K
D27
BAS21
ULVO
VCC
C84
R80
0.1uF 100K
1uF
1nF
CMPSH1-4
D24
C24
2
1
8
Q28
FDC2512
C55
CMPSH1-4
R22
15.0K
R18
365K
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin
C2
2.2uF
100V
3
C3-C5
3 X 2.2uF
100V
7
36V-72Vin
10
5
4
100pF
C27
100
R3
390
R78
BAS21
D29
10pF
T2
1
8
B
C51
1n
100V
C71
21
22
PT-
PT+
2.2nF
250V
C30
D31
MMBZ5258B
36V
D30
BAS21
1uF
R53
12
R52 Q25
10
1/4W
FMMT718
HAT2244WP
Q14
Q15
A
-VOUT
R51
10
1/4W
C69
1n
100V
11
10
8
-VOUT
SW
3
4
6
5
Q30
2N7002
R63
100K
C83
C66
680p
200V
5
6
4
3
PA0955(6:6:2:1)
1
T1 7
2
0.1uF
C101 C100
470pF 150pF
R101
100
5.1K
C72
R58
R48
10m
1.5W
Si7450DP
-VOUT Q8 Q9 Q11
T3
CT02-100
VCC
10n
C70
-VOUT
D26
CMPSH1-4
SW
R75
510
C78
10nF
Vsg
IS+
SG
HAT2244WP
Q12
Q13
10 1/4W -VOUT
-VOUT
-VOUT
R23
10 1/4W
R24
15
2
U2
LTC3706EGN
IS+
1
12
SG
R66
100K
150
C86
68pF
R82
R69
110K
L6
100
R56
150
R81
FCX491A
Q27
C67
10uF
25V
PA1494.242
Vaux
19
VIN
L5
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
NDRV
VSLMT
9
REGSD
17
C79
4.7n
R68
6.2K
240
Vsg
Q26
FMMT718
-VOUT
R102
6
10
11
Q32
FMMT619
VCC
FB
VS+
VS-
-VOUT
C77
2.2uF
C31 C68
16TQC68M
68u
16V
-VOUT
+
+VOUT
VCC
C34
10u
Q31
MMBT2907A
470p
C75
24
VCC
0.68uH
13
GATE
PGND
6
PGOOD
3
16
SLP
14
1
SG
FS/SYNC
IS
GND
11
PHASE
5
18
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin
R46
604
R41
11.5K
+Vout
-Vout
[email protected]
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 15. Single Phase Schematic
11
E2
1
1
P1-2
2
J1-2
2
P1-1
J1-1
6
4
T4
3
1
D
C
6
4
C
Vout/Iout
[email protected]
[email protected]
[email protected]
DC888A-A
DC888A-B
DC888A-C
C33
68uF, 16V
opt
220uF, 4V
220uF, 6.3V
C31,C68
D1
2
1
8
SSFLT
C29
10nF
10uF
22uF
22uF
C34
-VOUT
C85
0.1uF
1.0nF
4.7nF
2.2nF
680pF
C51,C69
C66
C27
100pF
C70
3.3nF
3.3nF
5
4
3
*
1
-VIN
R78
BAS21
D29
1
10pF
C83
11
10
8
7
T2
-VOUT
2.2nF
250V
C30
*
*
C71
*
-VOUT
36V
C75
47pF
470pF
100pF
C79
4.7nF
4.7nF
3.3nF
BAS21
opt.
opt.
D30
MMBZ5258B
opt.
opt.
D31
L6
21
22
R53
12
Q25
4
PT-
PT+
*
PA1382.650
PA1494.242
R23
opt.
Q8
SG
-VOUT
* C70
VCC
D26
CMPSH1-4
SW
Si7450DP
4
U2
LTC3706EGN
Vaux
opt.
R67
2
4
5
*
*
100
opt.
Si7336ADP
10
6.8
5.1
Vsg
11.5K
4.42K
2.74K
R41
Q26
FMMT718
-VOUT
*
C34
VS-
0.010
0.015
0.015
R48
FB
6
10
11
*
+ C33
VS+
VCC
Q32
FMMT619
VCC
*
C79
*
R64
OPT
R68
Q23,Q24 R23,R24,R51,R52
R102
Q31
MMBT2907A
C75
*
3
1
2
FCX491A
Q27
25V
C67
*
L6
R56
150
R81
R69 R70
0
110K
VCC
Si7336ADP
Q12-Q15
150
C86
68pF
R82
R66
100K
HAT2244WP
C78
10nF
IS+
321
Vsg
*
SG
Q12
Q13
Q23
8765
1/4W -VOUT
R75
510
*
1/4W
*R24
Si7450DP
-VOUT
PA1382.650
1uF
321
8765
Q14
Q15
Q24
C51
*100V
FMMT718
1/4W
D30
D31
1
8
B
R52
*
A
-VOUT
1/4W
R51
C69
*100V
SW
3
4
6
5
*
T1
Q30
2N7002
R63
100K
C82
opt.
C100
C101 150pF
470pF
R101
100
5
6
4
3
C66
*200V
* R48
1.5W
0.1uF
5.1K
C72
R58
123
5678
*
Q8
Q9 Q11
Si7450DP
1
2
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
opt.
C81
4
100
R3
0
R49
-VOUT
4.7uF 10nF
10uF
Vaux
FS/IN-
FB/IN+
10uF
C67
+VOUT
3
Q29
Si2303BDS
1.5nF
*
U1
1.5nF
*
2
R29
100K
* R76
* R84
3
4
LTC3725EMSE
R79
68K
D2
CMPSH1-4
R108
100uH
L1
R107
IS+
ULVO
C84
R80
0.1uF 100K
1uF
1nF
CMPSH1-4
D24
C24
3
VCC
C5
2.2uF
100V
Q28
FDC2512
C4
2.2uF
100V
C55
CMPSH1-4
R22
15.0K
* VERSION TABLE
D
DA2318-ALC
3
1
T4
VERSION
B
A
T4 connection for A-A
B
A
T4 connection for A-B & A-C
SSP
-VIN
R18
365K
-VIN
TO CONFIGURE
FOR POLYPHASE
-Vin
C3
2.2uF
100V
3
C2
2.2uF
100V
7
36V-72Vin
6
5
2
1
4
D27
BAS21
10
T3
CT02-100
15
2
IS+
1
12
19
VIN
L5
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
NDRV
9
VSLMT
1
3
16
SLP
GATE
PGND
6
REGSD
17
18 1
0.68uH
13
IS
GND
11
PGOOD
14
1
SG
FS/SYNC
24
VCC
E1
3
2
PHASE
5
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin
6.2K
9.1K
9.1K
R68
C74
OPT
-VOUT
*
+ C31
+VOUT
*
7.50
8.06
9.53
R76
R46
604
OPT
R62
R41
*
E3
390
620
750
R78
330
1.0K
2.2K
R84
-Vout
*
+Vout
C77
2.2uF
VCC
E4
+ C68
E8
-
+
E7
R59
P1-4
opt.
240
opt.
R102
4
3
P1-3
OPT
R74
OPT
OPT
R72
R71
OPT
R60
OPT
R73
opt.
0
opt.
R107
4
3
-VOUT
OPT
J1-6
P1-5
0
opt.
0
8
8
J1-8
T1
-VOUT
SSS
SYNC
-ITH
PA0955(6:6:2:1)
PA0954(4:4:1:1)
PA0950(6:6:1:1)
P1-11
11
J1-11
11
P1-10
10
J1-10
10
P1-9
9
J1-9
9
P1-8
R108
J1-4
J1-3
7
P1-7
J1-7 +ITH
7
+VPKS
-VPKS
J1-5
P1-6
6
6
5
5
TO CONFIGURE
FOR POLYPHASE
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 16. Full Single Phase Schematic
12
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Qty
Reference
Part Description
Manufacturer / Part #
1
REQUIRED CIRCUIT COMPONENTS
3
2
1
2
1
2
1
2
1
1
1
1
1
1
1
1
1
2
1
1
1
4
2
1
1
1
1
3
4
2
1
1
1
1
1
1
3
1
1
4
1
1
1
1
1
C3,C4,C5
C24,C71
C27,
C29,C78
C30
C31,C68
C34
C51,C69
C66
C67
C70
C75
C79
C55
C77
C72
C83
C84,C85
C86
C100
C101
D1,D2,D24,D26
D27,D29
D30
D31
L1
L6
Q11,Q9, Q8
Q12,Q13,Q14,Q15
Q25,Q26
Q27
Q28
Q29
Q30
Q31
Q32
R3,R56,R101
R18
R22
R23,R24,R51,R52
R41
R48
R68
R76
R78
CAP., X7R, 2.2uF, 100V, 20%, 1210
CAP., X7R, 1.0uF, 16V 10%, 0805
CAP., C0G, 100pF, 50V, 10%, 0603
CAP., X7R, 10nF, 50V, 10%, 0603
CAP., X7R, 2.2nF, 250V, 10%, 1812
POSCAP, 68uF, 16V, 20%, D3L case
CAP., X7R, 10uF, 16V, 10%, 1206
CAP., C0G, 1.0nF, 100V, 5%, 1206
CAP., C0G, 680pF, 200V, 10%, 1206
CAP., X7R, 4.7uF, 25V, 10%, 1210
CAP., X7R, 10nF, 50V, 10%, 0603
CAP., C0G, 470pF, 25V, 10%, 0603
CAP., X7R, 4.7nF, 50V, 10%, 0603
CAP., C0G, 1nF, 25V, 10%, 0603
CAP., X7R, 2.2uF, 16V, 20%, 1206
CAP., X7R, 0.1uF, 25V, 10%, 0805
CAP., C0G, 10pF, 50V, 10%, 0603
CAP., X7R, 0.1uF, 50V, 10%, 0603
CAP., C0G, 68pF, 25V, 10%, 0603
CAP., C0G, 150pF, 25V, 10%, 0603
CAP., C0G, 470pF, 25V, 10%, 0603
Diode Schottky, CMPSH1-4, 40V, SOT23
Diode, BAS21
SOT23
Diode, BAS21
SOT23
Diode, 36V
SOT23
INDUCTOR, 100uH, DO1606T
INDUCTOR, PLANAR, 2.4uH
FET, N-CH., Si7450DP, Powerpak SO-8
FET, N-CH., HAT2244WP, PW-PAK SO-8
TRANSISTOR, NPN, FMMT718, SOT23
TRANSISTOR, NPN, FCX491A, SOT89
FET, N-CH, FDC2512, SUPERSOT-6
FET, P-CH, 30-V(D-S) SOT-23
N-MOSFET, 2N7002 SOT23
TRANSISTOR, PNP, SOT-23
TRANSISTOR, NPN, SOT-23
RES., CHIP, 100, 1/16W, 5%, 0603
RES., CHIP, 365K, 1/8W, 1%, 0805
RES., CHIP, 15.0K, 1/16W, 1%, 0603
RES., CHIP, 10, 1/4W, 5%, 1206
RES., CHIP, 11.5K, 1/16W, 1%, 0603
RES., CHIP, 0.010, 1.5W, 2%, 2512
RES., CHIP, 6.2K, 1/16W, 5%, 0603
RES., CHIP, 7.50, 1/16W, 1%, 0805
RES., CHIP, 390, 1/16W, 5%, 0603
Murata, GRM32ER72A225K
TAIYO YUDEN, EMK212BJ105KG
AVX, 06035A101KAT2A
AVX, 06035C103KAT2A
Murata, GA343QR7GD222KW01L
Sanyo, 16TQC68M
TDK, C3216X7R1C106K
Murata, GRM3195C2A102JA01D
AVX, 12062A681KAT2A
Taiyo Yuden, TMK325BJ475KN
AVX, 06035C103KAT2A
AVX, 06033A471KAT2A
AVX, 06035C472KAT2A
AVX, 06033A102KAT2A
AVX, 1206YD225MAT2A
AVX, 08053C104KAT2A
AVX, 06035A100KAT2A
TDK, C1608X7R1H104K
AVX, 06033A680KAT2A
AVX, 06033A151KAT2A
AVX, 06033A471KAT2A
CENTRAL SEMI., CMPSH1-4-LTC
Diodes Inc., BAS21
Diodes Inc., BAS21
Diodes Inc., MMBZ5258B-7-F
Coilcraft, DO1606T-104MLC
PULSE, PA1494.242
VISHAY, Si7450DP
RENESAS, HAT2244WP
ZETEX, FMMT718
ZETEX, FCX491A
Fairchild, FDC2512_NL
VISHAY, Si2303BDS-T1-E3
Diodes Inc., 2N7002-7-F
DIODES., MMBT2907A-7-F
ZETEX, FMMT619
VISHAY, CRCW0603100RJNEA
VISHAY, CRCW0805365KFKEA
VISHAY, CRCW060315K0FKEA
VISHAY, CRCW120610R0JNEA
VISHAY, CRCW060311K5FKEA
IRC, LRC-LRF2512-01-R010-G
VISHAY, CRCW06036K20JNEA
VISHAY, CRCW08057R50FNEA
VISHAY, CRCW0603390RJNEA
13
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 17. Bill of Materials (Single Phase)
1
1
1
1
1
3
1
1
1
2
1
1
1
1
1
1
1
R84
R29
R46
R53
R58
R63,R66,R80
R69
R75
R79
R81,R82
R102
T1
T2
T3
T4
U1
U2
RES., CHIP, 330, 1/16W, 5%, 0805
RES., CHIP, 100K, 1/8W, 5%, 0805
RES., CHIP, 604, 1/16W, 1%, 0603
RES., CHIP, 12, 1/16W, 5%, 0603
RES., CHIP, 5.1K, 1/16W, 5%, 0603
RES., CHIP, 100K, 1/16W, 5%, 0603
RES., CHIP, 110K, 1/16W, 5%, 0603
RES., CHIP, 510, 1/16W, 5%, 0603
RES., CHIP, 68K, 1/8W, 5%, 0603
RES., CHIP, 150, 1/16W, 5%, 0603
RES., CHIP, 240, 1/16W, 5%, 0603
TRANSFORMER, PLANAR, 6:6:2:1
TRANSFORMER, PA1954NL
TRANSFORMER, CT02-100
TRANSFORMER,
1.5 : 1
I.C. LTC3725EMSE, MS10E
I.C. LTC3706EGN, SSOP-24GN
VISHAY, CRCW0805330RJNEA
VISHAY, CRCW0805100KJNEA
VISHAY, CRCW0603604RFKEA
VISHAY, CRCW060312R0JNEA
VISHAY, CRCW06035K10JNEA
VISHAY, CRCW0603100KJNEA
VISHAY, CRCW0603110KJNEA
VISHAY, CRCW0603510RJNEA
VISHAY, CRCW060368K0JNEA
VISHAY, CRCW0603150RJNEA
VISHAY, CRCW0603240RJNEA
PULSE, PA0955
PULSE, PA1954NL
ICE Components., CT02-100
Coilcraft, DA2318-ALC
LINEAR TECH., LTC3725EMSE#PBF
LINEAR TECH., LTC3706EGN#PBF
2
ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS
1
C2
CAP., X7R, 2.2uF, 100V, 20%, 1210
0
C33(opt)
POSCAP,
D3L case
0
C74(opt)
CAP.,
0603
0
C81,C82(opt.)
CAP.,
0603
1
L5
INDUCTOR, 0.68uH,
0
FET, N-CH.,
PW-PAK SO-8
Q23,Q24(opt)
2
R49,R70
RES., CHIP, 0, 1/16W, 0603
0
R59,R60.R62,R64,R67 RES., 0603
R71-R74(opt)
1
0
2
2
2
4
2
2
1
1
R107
R108(opt)
E1,E2
E8,E7
E3,E4
E3,E4(2 EACH)
E3,E4
E3,E4
J1
P1
RES., CHIP, 0, 1/16W, 0603
RES., 0603
TESTPOINT, TURRET, .094"
TESTPOINT, TURRET, .061"
STUD
NUT, BRASS, #10-32
WASHER, STAR #10 BRASS NICKEL
Ring, Lug Ring # 10
HEADER, SMD, single row, 2mm
SOCKET, SMD, single row, 2mm
Murata, GRM32ER72A225K
VISHAY, IHLP-2525CZERR68M01 e3
VISHAY, CRCW06030000Z0EA
VISHAY, CRCW06030000Z0EA
MILL-MAX, 2501-2-00-80-00-00-07-0
MILL-MAX, 2308-2-00-80-00-00-07-0
PEM, KFH-032-6
ANY
ANY
KEYSTONE 8205
Comm Com, 2SMD1-140/335/180-11G2
COMM COM, 1309-11G2
Notes:
1. Required Circuit Components are those parts that are required to implement the circuit function
2. Additional Demo Board Circuit Components are those parts that provide added functionality for the demo
board but are or may not be required in the actual circuit.
Figure 17. Bill of Materials (Single Phase) (cont’d)
14
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
SLAVE
MASTER
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Ref
Des
C29
C78
R71
R72
R74
C29
C78
C79
R41
R46
R59
R60
R62
R63
R64
R67
R68
R69
R70
R73
Single
Phase
10nF
10nF
OPT
OPT
OPT
10nF
10nF
4.7nF
11.5kΩ
604Ω
OPT
OPT
OPT
100kΩ
OPT
OPT
6.2kΩ
110kΩ
0Ω
OPT
PolyPhase
4.7nF
4.7nF
0Ω
0Ω
0Ω
4.7nF
4.7nF
open
open
open
0Ω
0Ω
0Ω
open
0Ω
0Ω
open
open
open
0Ω
Figure 18. Single Phase to PolyPhase Electrical Component Changes
15
1
1
2
1
P1-1
B
A
J1-2
6
4
2
T4
3
1
D
C
P1-2
DA2318-ALC
2
SSP (to SSP SLV)
1
E1
E2
-VIN (to SLV)
2
-Vin (to SLV)
J1-1
E2
E1
+Vin (to SLV)
D1
2
IS+
U1
7.5
Q29
Si2303BDS
-VOUT
C85
0.1uF
D2
CMPSH1-4
100uH
L1
R29
100K
3
R76
330
R84
4
Vaux
FS/IN-
FB/IN+
LTC3725EMSE
R79
68K
C29
4.7nF
SSFLT
ULVO
VCC
C84
R80
0.1uF 100K
1uF
1nF
CMPSH1-4
D24
C24
SSP
1
8
Q28
FDC2512
C55
CMPSH1-4
R22
15.0K
R18
365K
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin
D27
BAS21
VSLMT
9
C3-C5
3 X 2.2uF
100V
6
C2
2.2uF
100V
10
36V-72Vin
3
NDRV
7
GATE
PGND
5
4
100pF
C27
100
R3
390
R78
10pF
C83
T2
1
FMMT718
21
22
PT-
PT+
2.2nF
250V
C30
D31
MMBZ5258B
36V
D30
BAS21
1uF
SYNC
R53
12
R52 Q25
10
1/4W
C71
8
B
C51
1n
100V
HAT2244WP
Q14
Q15
-VOUT
R51
10
1/4W
C69
1n
100V
11
10
8
-VOUT
SW
3
4
6
5
Q30
2N7002
R63
100K
BAS21
D29
5
6
4
3
C66
680p
200V
C101 C100
470pF 150pF
R101
100
0.1uF
5.1K
C72
R58
R48
10m
1.5W
Si7450DP
-VOUT Q8 Q9 Q11
A
VCC
10n
C70
-VOUT
D26
CMPSH1-4
SW
R75
510
C78
4.7nF
SSS
Vsg
IS+
SG
U2
LTC3706EGN
SG
R66
100K
150
C86
68pF
R82
L6
100
R56
150
R81
C79
4.7n
R68
6.2K
240
+
VS-
6
10
Q26
FMMT718
Vsg
Q32
FMMT619
VCC
FB
11
-VOUT
VS+
VCC
C77
2.2uF
C31 C68
16TQC68M
68u
16V
-VOUT
-VOUT
R102
Q31
MMBT2907A
-ITH
470p
C75
+ITH
FCX491A
Q27
-VPKS
+VPKS
C67
10uF
25V
C34
10u
+VOUT
MASTER
PA1494.242
Vaux
R69
110K
HAT2244WP
Q12
Q13
10 1/4W -VOUT
-VOUT
-VOUT
R23
10 1/4W
R24
15
PA0955(6:6:2:1)
1
T1 7
2
12
IS
GND
11
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
IS+
T3
CT02-100
3
16
SLP
2
REGSD
17
19
VIN
1
13
18
L5
PGOOD
14
1
SG
FS/SYNC
24
VCC
0.68uH
PHASE
5
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin
R46
604
R41
11.5K
3
E3
E3
4
E4
E4
5
5
P1-5
6
6
P1-6
7
7
P1-7
8
8
P1-8
9
9
P1-9
10
10
P1-10
J1-11
11
11
P1-11
-VOUT (to SLV)
J1-10
SSS (to SSS SLV)
J1-9
SYNC (to SYNC SLV)
J1-8
-ITH (to -ITH SLV)
J1-7
+ITH (to +ITH SLV)
J1-6
+VPKS (to +VPKS SLV)
J1-5
-VPKS (to -VPKS SLV)
4
-Vout (to -Vout SLV)
3
+Vout (to +Vout SLV)
-Vout
[email protected]
+Vout
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 19. PolyPhase Master Schematic
16
1
2
1
P1-1
E2
E1
B
A
J1-2
6
4
T4
2
3
1
D
C
P1-2
DA2318-ALC
2
SSP (to SSP SLV)
1
-VIN (to SLV)
2
-Vin (to SLV)
1
+Vin (to SLV)
J1-1
E2
E1
D1
CMPSH1-4
D24
2
1
IS+
L1
U1
Q29
Si2303BDS
-VOUT
C85
0.1uF
D2
CMPSH1-4
100uH
R29
100K
7.5
R76
330
R84
3
Vaux
FS/IN-
FB/IN+
LTC3725EMSE
R79
68K
C29
4.7nF
SSFLT
ULVO
VCC
C84
R80
0.1uF 100K
C24
1uF
1nF
SSP
8
Q28
FDC2512
C55
CMPSH1-4
R22
15.0K
R18
365K
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin
D27
BAS21
VSLMT
9
C3-C5
3 X 2.2uF
100V
6
C2
2.2uF
100V
4
10
36V-72Vin
3
NDRV
7
GATE
PGND
R3
5
4
100pF
C27
100
390
R78
BAS21
D29
5
6
4
3
T2
1
8
B
Q14
Q15
21
22
PT-
PT+
2.2nF
250V
C30
D31
MMBZ5258B
36V
D30
BAS21
1uF
C71
R53
12
R52 Q25
10
1/4W
FMMT718
HAT2244WP
A
-VOUT
R51
10
1/4W
C69
1n
100V
11
10
8
-VOUT
SW
3
4
6
5
Q30
2N7002
10pF
C83
C66
680p
200V
C101 C100
470pF 150pF
R101
100
0.1uF
5.1K
C72
R58
R48
10m
1.5W
Si7450DP
-VOUT Q8 Q9 Q11
PA0955(6:6:2:1)
1
T1 7
2
C51
1n
100V
VCC
10n
C70
-VOUT
D26
CMPSH1-4
SW
R75
510
C78
4.7nF
SSS
Vsg
IS+
SG
HAT2244WP
Q12
Q13
10 1/4W -VOUT
-VOUT
-VOUT
R23
10 1/4W
R24
15
T3
CT02-100
12
IS
GND
11
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
U2
LTC3706EGN
IS+
2
R66
100K
SG
REGSD
17
150
C86
68pF
R82
SYNC
L6
100
R56
150
R81
VCC
FCX491A
Q27
C67
10uF
25V
240
6
10
11
VCC
+ITH
-ITH
Q26
FMMT718
Vsg
Q32
FMMT619
VCC
-VOUT
R102
Q31
MMBT2907A
470p
C75
FB
VS+
VS-
-VOUT
C77
2.2uF
C31 C68
16TQC68M
68u
16V
-VOUT
+
+VOUT
VCC
C34
10u
SLAVE
PA1494.242
Vaux
19
VIN
1
13
18
L5
PGOOD
3
16
SLP
14
1
SG
FS/SYNC
24
VCC
0.68uH
PHASE
5
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin
+Vout
3
E3
E3
4
E4
E4
5
5
P1-5
6
6
P1-6
7
7
P1-7
8
8
P1-8
9
9
P1-9
J1-10
10
10
P1-10
SSS (to SSS SLV)
J1-9
SYNC (to SYNC SLV)
J1-8
-ITH (to -ITH SLV)
J1-7
+ITH (to +ITH SLV)
J1-6
+VPKS (to +VPKS SLV)
J1-5
-VPKS (to -VPKS SLV)
4
-Vout (to -Vout SLV)
3
+Vout (to +Vout SLV)
-Vout
[email protected]
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 20. PolyPhase Slave Schematic
17
-VIN
1
6
4
T4
3
1
D
C
T4
6
4
Vout/Iout
[email protected]
[email protected]
[email protected]
VERSION
DC888A-B
DC888A-C
D1
C33
68uF, 16V
opt
220uF, 4V
220uF, 6.3V
C31,C68
3
2
1
8
2.2nF
10uF
1.0nF
4.7nF
1.5nF
22uF
680pF
C51,C69
C66
C34
1.5nF
*
+VOUT
22uF
-VOUT
*
U1
* R76
3
Q29
Si2303BDS
C85
0.1uF
D2
CMPSH1-4
R108
100uH
L1
2
R29
100K
3
* R84
4
100pF
C27
10nF
15nF
15nF
C70
Vaux
FS/IN-
FB/IN+
LTC3725EMSE
R79
68K
4.7nF
SSFLT
C29
R107
IS+
ULVO
VCC
C84
R80
0.1uF 100K
1uF
1nF
CMPSH1-4
D24
C24
C55
CMPSH1-4
R22
15.0K
R18
365K
* VERSION TABLE
D
DA2318-ALC
3
1
DC888A-A
B
A
C
T4 connection for A-A
B
A
T4 connection for A-B & A-C
P1-2
2
J1-2
2
SSP (to SSP SLV)
P1-1
J1-1
1
-VIN (to SLV)
C5
2.2uF
100V
Q28
FDC2512
C4
2.2uF
100V
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin (to SLV)
E2
C3
2.2uF
100V
3
C2
2.2uF
100V
6
5
2
1
4
D27
BAS21
7
36V-72Vin
10
470pF
100pF
47pF
C75
5
opt.
C81
4
100
R3
0
R49
-VOUT
T3
CT02-100
4
4.7nF
3.3nF
*
1
1
10pF
C83
*
11
10
8
7
T2
-VOUT
*
C71
*
PA1382.650
PA1494.242
PA1382.650
-VOUT
36V
D31
21
22
R53
12
Q25
L6
1uF
321
8765
4
Q14
Q15
Q24
C51
*100V
FMMT718
1/4W
D30
1
8
B
R52
*
A
-VOUT
MMBZ5258B
opt.
opt.
D31
2.2nF
250V
C30
*
1/4W
R51
C69
*100V
SW
3
4
6
5
Q30
2N7002
BAS21
opt.
opt.
D30
-VIN
R78
BAS21
4.7nF
C79
3
D29
R63
100K
C82
opt.
C100
C101 150pF
470pF
R101
100
5
6
4
3
C66
*200V
* R48
1.5W
0.1uF
5.1K
C72
R58
123
5678
*
Q8
Q9 Q11
Si7450DP
1
2
T1
*
PT-
PT+
SG
Si7450DP
C70
-VOUT
*
VCC
D26
CMPSH1-4
SW
C78
U2
LTC3706EGN
R82
R66
100K
HAT2244WP
150
R81
100
R56
opt.
R67
C75
*
R102
*
opt.
R41
4.42K
11.5K
10
2.74K
FB
VS+
0.010
0.015
0.015
6
6.2K
9.1K
9.1K
R68
10
11
*
+ C33
VS-
R48
Vsg
Q26
FMMT718
-VOUT
*
C34
VCC
Q32
FMMT619
VCC
*
C79
*
OPT
R68
R64
6.8
5.1
3
FCX491A
Q27
Q31
MMBT2907A
R69 R70
0
110K
VCC
2
1
2
C67
10uF
25V
*
L6
Q23,Q24 R23,R24,R51,R52
Si7336ADP
Si7336ADP
Q12-Q15
150
C86
68pF
4.7nF
IS+
321
4
Vaux
4
5
MASTER
Vsg
*
SG
Q12
Q13
Q23
8765
1/4W -VOUT
R75
510
*
Si7450DP
opt.
Q8
-VOUT
R23
1/4W
*R24
15
2
IS+
1
12
NDRV
9
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
19
VIN
L5
3
16
SLP
GATE
PGND
6
VSLMT
1
REGSD
17
18 1
0.68uH
13
IS
GND
11
PGOOD
14
1
SG
FS/SYNC
24
VCC
E1
3
2
PHASE
5
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin (to SLV)
C74
OPT
7.50
8.06
9.53
R76
-VOUT
*
+ C31
+VOUT
*
R84
330
390
2.2K
1.0K
opt.
240
R74
4
3
opt.
0
opt.
J1-6
J1-4
J1-3
opt.
0
0
R108
4
3
8
9
10
PA0955(6:6:2:1)
PA0954(4:4:1:1)
PA0950(6:6:1:1)
T1
-VOUT (to SLV)
P1-11
11
J1-11
11
P1-10
10
J1-10
SSS (to SSS SLV)
P1-9
9
J1-9
SYNC (to SYNC SLV)
P1-8
J1-8
8
-ITH (to -ITH SLV)
P1-7
7
7
J1-7
+ITH (to +ITH SLV)
+VPKS (to +VPKS SLV)
P1-5
-VPKS (to -VPKS SLV)
J1-5
P1-6
6
6
5
5
-VOUT
OPT
R107
P1-4
P1-3
0ohms
R102
opt.
0ohms
0ohms R73
R72
R71
OPT
R60
OPT
R59
-Vout (to -Vout SLV)
*
+Vout (to +Vout SLV)
C77
2.2uF
VCC
E4
620
750
R78
R46
604
OPT
R62
R41
*
E3
+ C68
E8
-
+
E7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 21. Full PolyPhase Master Schematic
18
E2
-VIN
C3
2.2uF
100V
1
1
6
4
T4
3
1
D
C
B
A
6
4
C
D1
Vout/Iout
[email protected]
[email protected]
[email protected]
VERSION
DC888A-A
DC888A-B
DC888A-C
C33
68uF, 16V
opt
100uH
L1
*
10uF
22uF
22uF
C34
*
2
R29
100K
U1
* R76
* R84
3
2.2nF
1.0nF
4.7nF
1.5nF
680pF
C51,C69
C66
+VOUT
Vaux
FS/IN-
1.5nF
C85
0.1uF
3
Q29
Si2303BDS
100pF
C27
10nF
15nF
15nF
C70
5
opt.
C81
4
100
R3
0
R49
-VOUT
T3
CT02-100
FB/IN+
LTC3725EMSE
R79
68K
4.7nF
SSFLT
C29
R107
IS+
ULVO
D2
CMPSH1-4
R108
-VOUT
220uF, 4V
220uF, 6.3V
C31,C68
2
1
8
C84
R80
0.1uF 100K
1uF
1nF
CMPSH1-4
D24
C24
3
VCC
C5
2.2uF
100V
Q28
FDC2512
C4
2.2uF
100V
C55
CMPSH1-4
R22
15.0K
R18
365K
* VERSION TABLE
D
DA2318-ALC
3
1
T4
T4 connection for A-A
B
A
T4 connection for A-B & A-C
P1-2
2
J1-2
SSP (to SSP MSTR) 2
P1-1
J1-1
-VIN (to MSTR)
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin (to MSTR)
C2
2.2uF
100V
6
5
2
1
4
D27
BAS21
3
4
10
36V-72Vin
7
2
4
*
470pF
*
1
1
10pF
C83
BAS21
*
11
10
8
7
T2
C30
-VOUT
*
C71
*
PA1382.650
PA1494.242
PA1382.650
-VOUT
36V
D31
21
22
R53
12
Q25
L6
1uF
321
8765
4
Q14
Q15
Q24
C51
*100V
FMMT718
1/4W
D30
1
8
B
R52
*
A
-VOUT
MMBZ5258B
opt.
opt.
D31
2.2nF
250V
*
1/4W
R51
C69
*100V
SW
3
4
6
5
Q30
2N7002
opt.
opt.
D30
-VIN
R78
BAS21
100pF
47pF
C75
3
D29
R63
100K
C82
opt.
C100
C101 150pF
470pF
R101
100
5
6
4
3
C66
*200V
R48
1.5W
0.1uF
5.1K
C72
R58
123
5678
*
Q8
Q9 Q11
Si7450DP
1
2
T1
*
PT-
PT+
SG
Si7450DP
* C70
VCC
-VOUT
D26
CMPSH1-4
SW
C78
U2
LTC3706EGN
R82
R66
100K
HAT2244WP
150
100
VCC
*
R102
opt.
10
6.8
5.1
Q26
FMMT718
R48
0.010
0.015
0.015
FB
7.50
8.06
9.53
R76
Vsg
Q32
FMMT619
-VOUT
Q31
MMBT2907A
*
C79
*
VS-
6
390
620
750
R78
10
11
*
+ C33
VS+
VCC
*
C34
0ohms
R64
R68
C75
*
3
FCX491A
Q27
1
2
0ohms
R67
2
*
25V
C67
*
L6
R69 R70
0
110K
VCC
R81
R56
Vaux
4
5
SLAVE
Q23,Q24 R23,R24,R51,R52
Si7336ADP
Si7336ADP
Q12-Q15
150
C86
68pF
4.7nF
IS+
321
4
Vsg
*
SG
Q12
Q13
Q23
8765
1/4W -VOUT
R75
510
*
Si7450DP
opt.
Q8
-VOUT
R23
1/4W
*R24
15
1
IS+
L5
19
VIN
0.68uH
12
NDRV
9
VSLMT
1
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
GATE
PGND
6
REGSD
17
IS
GND
11
PGOOD
3
16
SLP
14
1
SG
FS/SYNC
13
24
VCC
E1
3
2
PHASE
5
18 1
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin (to MSTR)
C74
OPT
330
1.0K
2.2K
R84
-VOUT
*
+ C31
+VOUT
*
opt.
240
opt.
R102
R46
604
E4
opt.
0
opt.
R107
R73
opt.
0
0
R108
0ohms
4
3
T1
4
3
-VOUT
8
P1-9
9
J1-9
9
P1-8
J1-8
8
-ITH (to -ITH MSTR)
P1-7
7
7
J1-7
J1-4
J1-3
PA0955(6:6:2:1)
PA0954(4:4:1:1)
11
P1-11
11
J1-11
-VOUT (to MSTR)
P1-10
10
10
J1-10
SSS (to SSS MSTR)
SYNC (to SYNC MSTR)
P1-6
+ITH (to +ITH MSTR)
+VPKS (to +VPKS MSTR)
P1-5
J1-5
-VPKS (to -VPKS MSTR)
J1-6
6
6
5
5
PA0950(6:6:1:1)
P1-4
P1-3
OPT
R74
OPT
OPT
R72
R71
0ohms
R60
0ohms
R59
-Vout (to -Vout MSTR)
*
+Vout (to +Vout MSTR)
C77
2.2uF
VCC
0ohms
R62
R41
*
E3
+ C68
E8
-
+
E7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 22. Full PolyPhase Slave Schematic
19
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-C
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 23. Picture of two DC888A’s configured for PolyPhase
20
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