QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 447
2-PHASE DUAL OUTPUT POWER SUPPLY
LTC3728EUH
DESCRIPTION
Demonstration circuit 447 is a step-down converter fea-
turing the LTC3728EUH regulator. The PolyPhase
TM
dual
output controller LTC3728EUH drives two high current
synchronous buck converters. Input is 5V–14V, output 1
is 2.5V with loads up to 13A and output 2 is 1.8V with
loads up to 13A.
For applications with input voltage less than 5V, DC447
includes a circuit footprint on the bottom side to provide
a 5V bias power supply.
Design files for this circuit board are available. Call
the LTC factory.
Table 1.
Performance Summary
PARAMETER CONDITION VALUE
Minimum Input Voltage 5V
Maximum Input Voltage 14V
V
OUT1
V
IN
= 5V to 14V, I
OUT1
= 0A to 13A 2.5V
V
OUT2
V
IN
= 5V to 14V, I
OUT1
= 0A to 13A 1.8V
Nominal Switching Frequency 450kHz
QUICK START PROCEDURE
Demonstration circuit 447 is easy to set up to evaluate
the performance of the LTC3728EUH. Refer to Figure 1
for proper measurement equipment setup and follow the
procedure below:
NOTE:
When measuring the input or output voltage rip-
ple, care must be taken to avoid a long ground lead on
the oscilloscope probe. Measure the input or output
voltage ripple by touching the probe tip directly across
the input or output and ground terminals. See Figure 2
for proper scope probe technique.
1.
Before powering up, place the jumpers as shown in
Figure 1.
2.
Connect the loads at VOUT1 and VOUT2. Set the load
current to 0A.
3.
With the power off, connect the input 5V–14V (rec-
ommended 12V) power supply to VIN and GND.
VOUT1 should be within 2.5V ±0.1V and VOUT2
should be 1.8V ±0.1V.
4.
Increase the load at VOUT1 to 13A. With a 12V input,
the input current should be less than 3.5A. Slowly de-
crease the input voltage to 5V. At 5V input voltage, the
input current should be less than 8A.
5.
Decrease the load at VOUT1 to 0A. Increase the input
voltage to 12V.
6.
Increase the load on VOUT2 to 13A. With a 12V input,
the input current should be less than 2.5A. Slowly de-
crease the input voltage to 5V. At 5V input, the input
current should be less than 6A.
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 447
2-PHASE DUAL OUTPUT POWER SUPPLY
+
–
+
–
+
–
+–
+–
LOAD
+
–
LOAD
+
–
+
–
+–
VIN
GND
Figure 1.
Proper Measurement Equipment Setup
Figure 2.
Scope Probe Placement for
Measuring Input or Output Ripple
2
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
2.5V@13A
1.8V@13A
5V-14V
OPTIONAL DISTRIBUTED CAPS
2. R23=R24=R25=0 OHM WILL B E ASSEMBLED ONLY
IF TWO OUTPUTS ARE TIED TOGETHER FOR HIGH
CURRENT OUTPUT.
NOTES: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTORS ARE IN OHMS, 0603.
TOKO, FSLM2520-4R7
3. INSTALL SHUNTS ON JP1-JP5 PIN 2 AND 3.
IF VIN<5V, INSTALL SHUNTS ON JP4 AND JP5
PIN 1 AND 2.
RUN/SS1
RUN/SS2
ON OFF
ON OFF
FCB
P.S.BM. C.C.M
OPTIONAL BIAS CIRCUIT
<5VIN>5VIN
BIAS INPUT
<5VIN
INPUT SEL.
>5VIN
A
Friday, August 02, 2002 1 1
2-PHASE DUAL OUTPUT PO WER SUPPLY
KIM T.
WEI C.
ADC447A-1 * LTC37 28EUH
SIZE
DATE:
DWG NO. REV
SHEET OF
TITLE:
CONTRACT NO.
APPROVALS
DRAWN:
CHECKED:
APPROVED:
ENGINEER:
DESIGNER:
TECHNOLOGY Fax: (408)434-0507
Milpitas, CA 95035
Phone: (408)432-1900
1630 McCarthy Blvd.
LTC Confidential-For Customer Use Only
VOUT2
5VBIAS
5VBIAS
PG
INTVCC
SYNC
VO1SEN
VIN
VOUT1
VIN
VOUT1
VOUT2
VIN
VOUT1
VOUT2
VIN
R14
20.5K
1%
D2
CMDSH-3
21
L3
4.7UH
C15
0.01UF
R8
10
C58
1210
C40
1210
R4
30K
+
C69
180UF 4V
7343
C30
10UF
10V
1206
Q1
Si7860DP
4
5 1
3
26
7
8
C42
1210
+C11
56UF,25V
OSCON
C47
1210
D4
B320A
21
C10
1UF
0603
+C68
7343
C56
1210
JP1
13
2
E6
VO2SEN
R25
OPT
Q2
Si7856DP
4
51
3
2 6
7
8
+
C70
220UF 2.5V
C65 OPT +
C4
180UF 4V
7343
C14 1000PF
C45
1210
C1
0.1UF
C12
4.7UF
25V
1210
R24
OPT
C2
180PF
C3
1000PF
+C32
7343
C13
4.7UF
25V
1210
C16 33PF
+C67
7343
R13
26.1K
1%
C31
OPT
R11 15K
R26
10
U1
LTC3728EUH
28
30
31
1
2
3
4
5
6
15
17
14
19
20
21
22
23
24
27
187
8
9
11
12 13
25
26
RUN/SS1
SENSE1+
SENSE1-
VOSENSE1
FREQSET
PLLIN
FCB
ITH1
SGND
SW2
BOOST2
TG2
PGND
INTVCC
EXTVCC
BG1
VIN
BOOST1
PG
BG23.3VOUT
ITH2
VOSENSE2
SENSE2-
SENSE2+ RUN/SS2
SW1
TG1
E2SYNC
C9 33PF
R19
100K
C57
1210
R18
10
E5
VO1SEN
C19
180PF
D1
B320A
2 1
R28
10
C24
4.7UF
25V
1210
C46
1210
JP5
13
2
L1
1.3UH
L1 & L2= SUMIDA
CDEP105-1R3MC-50
C59
1210
C20
1000PF
J4
GND
C26
OPT
0603
1UF
C66
OPT
C25
4.7UF
25V
1210
C5
0.1UF
Q5
OPT
4
5 1
3
26
7
8
C48
1210
C17
0.1UF
R16
1M
R17
10
Q6
OPT
4
51
3
2 6
7
8
C55
1210
R3
0.003
2512
R9
1M
C29
10UF
10V
1206
C27
0603
1UF
C60
1210
R1
10
C44
1210
Q8
OPT
4
5 1
3
26
7
8
R21
37.4K
R2
10
C63
1210
D5
CMDSH-3
2 1
JP3
13
2
U2
LT1613
SOT23-5
2
15
4
3GND
SWVIN
SD
FB
C49
1210
E3
INTVCC
C52
1210
C62
1210
C23
0.1UF
L2
1.3UH
C51
1210
C34
1210
R7
11.8K
R22
12.1K
C64
1210
C35
1210
C61
1210
C33
1210
J1
VOUT1
R5
43.2K
1%
E4
5VBIAS
R15
0.003
2512
C6 1000PF
C36
1210
JP2
1 3
2
C53
1210
Q7
OPT
4
51
3
2 6
7
8
C21
0.01UF
C7
1UF 16V
0805
C28
0603
1UF
C50
1210
J2
GND
D3
CMDSH-3
21
R23 OPT
C37
1210
R10 15K C8
4.7UF
10V
0805
R20 100K
C39
1210
J3
VIN
E1PG
+C54
7343
+
C22
220UF 2.5V
R27
1
C38
1210
R6 20K
1%
Q3
Si7860DP
4
51
3
2 6
7
8
J5
VOUT2
J6
GND
JP4
1 3
2
+C43
7343
C41
1210
Q4
Si7856DP
4
5 1
3
26
7
8
5VBIAS
