DEMO MANUAL DC2358A
LTM8068
Isolated μModule DC/DC Converter
with LDO Regulator
DESCRIPTION
The Demo Circuit 2358A is a 2kV AC isolated flyback
μModule
®
DC/DC converter with LDO post regulator featur-
ing the
LTM8068.
The demo circuit is designed for a 5.6V
flyback output and a 5V post regulator output from a 4.5V
to 40V input. The current capability of the 5.6V flyback
output varies with input voltage from about 200mA at
4.5V
IN
to about 460mA at 40V
IN
. The current capability of
the 5V LDO output is limited by either the current capabil-
ity of V
OUT1
minus V
OUT1
loading or the 300mA current
limit on the LDO post regulator itself. Figure 1 shows the
maximum output current on V
OUT1
when V
OUT2
is not
loaded, and V
OUT2
when V
OUT1
is unloaded. V
OUT2
is the
LDO post regulator from V
OUT1
.
The two-stage converter provides an isolated flyback output
as well as a low-noise LDO output. Figure 2 shows the
output noise spectrum on the flyback output and Figure
3 shows the output noise spectrum on the LDO output.
The LTM8068 data sheet gives complete description of
the device, operation and application information. The
data sheet must be read in conjunction with this quick
start guide for demo circuit 2358A.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2358A
L,
LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
BOARD PHOTO
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DEMO MANUAL DC2358A
PERFORMANCE SUMMARY
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
Output Voltage V
OUT1
Output Voltage V
OUT2
Voltage Ripple V
OUT1
Voltage Ripple V
OUT2
V
IN
= 4.5V to 40V
V
IN
= 4.5V to 40V
V
IN
= 12V, I
OUT1
= 200mA, I
OUT2
= 0mA
V
IN
= 12V, I
OUT1
= 0mA, I
OUT2
= 200mA
40
5.3
4.85
5.6
5
25
1
5.9
5.15
CONDITIONS
Specifications are at T
A
= 25°C
MIN
TYP
MAX
4.5
UNITS
V
V
V
V
mV
mV
500
MAXIMUM LOAD CURRENT (mA)
5.6V
OUT1
5V
OUT2
0
0
400
INTENSITY (dBm)
–20
INTENSITY (dBm)
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
FREQUENCY (MHz)
dc2358 F02
–20
300
–40
–40
200
–60
–60
100
–80
–80
0
0
10
20
V
IN
(V)
30
40
dc2358 F01
–100
0
–100
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
FREQUENCY (MHz)
dc2358 F03
Figure 1. Maximum Output Current vs
V
IN
: 5.6V
OUT1
Flyback Output with V
OUT2
Unloaded; 5V
OUT2
LDO output with
V
OUT1
Unloaded
Figure 2. V
OUT1
Output Noise Spectrum
with I
OUT1
at 200mA and V
IN
at 12V
(V
OUT2
Has No Extra Load)
Figure 3. V
OUT2
Output Noise Spectrum
with I
OUT2
at 200mA and V
IN
at 12V
(V
OUT1
Has No Extra Load)
QUICK START PROCEDURE
Demo circuit 2358A is easy to set up to evaluate the per-
formance of the LTM8068. Refer to Figure 4 for proper
measurement equipment setup and 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
oscilloscope probe. Measure the input or output voltage
ripple by touching the probe tip directly across the V
IN
and GND or V
OUT
and V
OUTN
terminals. See Figure 5 for
proper scope probe technique.
1. With power off, connect the input power supply to V
IN
and GND.
2. Turn on the power at the input.
NOTE. Make sure that the input voltage does not
exceed 40V.
3. Check for the proper output voltages. (For OUT1, check
the voltage between V
OUT1
and V
OUTN
. For OUT2, check
the voltage between V
OUT2
and V
OUTN
.)
NOTE: If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
4. Once the proper output voltages are established, adjust
the load within the operating range and observe the
output voltage regulation, ripple voltage, efficiency and
other parameters.
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DEMO MANUAL DC2358A
QUICK START PROCEDURE
Figure 4. DC2358A Proper Equipment Setup
INPUT OR OUTPUT CAPACITOR
Figure 5. Measuring Input or Output Ripple
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DEMO MANUAL DC2358A
PARTS LIST
ITEM
1
2
3
4
5
6
7
8
9
10
11
12
13
1
2
3
4
1
2
3
QTY
1
1
2
1
1
1
1
1
1
1
1
1
1
0
0
0
0
6
1
4
REFERENCE
CIN1
C1
C2, C3
C4
C5
C8
C10
R1
R2
R3
R4
R5
U1
C6 (OPT)
C7 (OPT)
C9 (OPT)
L1 (OPT)
E1-E6
E7
MH1-MH4
PART DESCRIPTION
CAP ALUM, 22µF, 50V, 6.6x6.6mm
.,
CAP CER., 10µF, X7R, 50V, 10%, 1210
.,
CAP CER., 4.7µF, X5R, 10V, 10%, 0603
.,
CAP CER., 47µF, X5R, 10V, 10%, 1206
.,
CAP CER., 22µF, X5R, 6.3V, 20%, 0805
.,
CAP CER., 0.01µF, X7R, 25V, 10%, 0603
.,
CAP CER., 10pF, NP0, 50V, 5%, 0603
.,
RES, 200k, 1/10W, 1%, 0603
RES, 95.3k, 1/10W, 1%, 0603
RES, 7.32k, 1/10W, 1%, 0603
RES, 604Ω, 1/8W, 1%, 0805
RES, 162k, 1/10W, 1%, 0603
I.C., LTM8068EY#PBF 9 × 11.25 × 4.92 BGA
CAP 1210 (OPT)
.,
CAP 0805 (OPT)
.,
CAP 1808 (OPT)
.,
IND., 10µH, XFL3012 (OPT)
TESTPOINT, TURRET, 0.094" pbf
TEST POINT, TURRET, 0.064" MTH HOLE
STAND-OFF NYLON 0.375" SNAP ON
,
MILL-MAX, 2501-2-00-80-00-00-07-0
MILL-MAX, 2308-2-00-80-00-00-07-0
KEYSTONE, 8832
MANUFACTURER/PART NUMBER
NICHICON, UUD1H220MCL1GS
MURATA, GRM32ER71H106KA12L
MURATA, GRM188R61A475KE15D
MURATA, GRM31CR61A476KE15L
MURATA, GRM21BR60J226ME39L
MURATA, GRM188R71E103KA01D
MURATA, GRM1885C1H100JA01D
VISHAY, CRCW0603200KFKEA
VISHAY, CRCW060395K3FKEA
VISHAY, CRCW06037K32FKEA
VISHAY, CRCW0805604RFKEA
VISHAY, CRCW0603162KFKEA
LINEAR TECH., LTM8068EY#PBF
Required Circuit Components
Additional Demo Board Circuit Components
Hardware: For Demo Board Only
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4
A
B
C
D
E
4
U1
LTM8068EY
L1
VIN
C1
10uF
50V
1210
G1
G2
H1
H2
VIN
VIN
VIN
VIN
VOUT1
VOUT1
VOUT1
VOUT1
4
VIN
4.5V - 40V
C6
OPT
1206
C4
47uF
10V
1206
R4
604
0805
C2
4.7uF
10V
E3
E1
VIN
SCHEMATIC DIAGRAM
+
CIN1
*
OPT
R1
200k
F3
RUN
B1
A1
VOUTN
VOUTN
VOUTN
VOUTN
VOUTN
VOUTN
B5
B4
B3
A5
A4
A3
B7
B6
A7
A6
GND
22uF
50V
VOUT1
5.6V
**
E4
VOUTN
E2
3
RUN
R2
95.3k
VOUT2
VOUT2
E7
C7
OPT
0805
3
BYP
FB2
FB1
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
A2
B2
C8
0.01uF
25V
C5
22uF
6.3V
0805
C3
4.7uF
10V
E5
VOUT2
5V
**
E6
VOUTN
G7
E1
E2
E3
E4
E5
E6
E7
F4
F5
F6
F7
G4
G5
G6
H4
H5
H6
H7
R5
162k
1%
2
C10
10pF
R3
7.32k
C9
OPT
1808
2
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.
B
C
D
*
FOR INPUT VOLTAGE DAMPING PURPOSE ONLY.
**
SEE QUICK START GUIDE FOR OUTPUT CURRENT RANGE.
NOTE: UNLESS OTHERWISE SPECIFIED
1. ALL RESISTORS ARE 0603.
ALL CAPACITORS ARE 0603.
1
1
A
E
DEMO MANUAL DC2358A
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