Document 704-1
Coupled Inductors – MSD1278T
For high temperature
SEPIC applications
The MSD1278T series of coupled inductors was de-
signed for high temperature applications – up to 125°C.
The excellent coupling coefficient (k
≥
0.94) makes it
ideal for use in SEPIC applications. In SEPIC topolo-
gies, the required inductance for each winding in a
coupled inductor is half the value needed for two sepa-
rate inductors, allowing selection of a part with lower
DCR and higher current handling.
These inductors provide high inductance, high effi-
ciency and excellent current handling in a rugged, low
cost part. They are well suited for use as VRM induc-
tors in high-current DC-DC and VRM/VRD controllers.
They can also be used as two single inductors con-
nected in series or parallel, as a common mode choke
or as a 1 : 1 transformer.
0.484
max
12,3
D1
+
L1
C1
Dot indicates pin1
Dash number
Internal code
+
+
V
OUT
0.484
max
12,3
123
X
V
IN
Q1
L2
C2
Load
–
–
Typical SEPIC schematic
0.308 ±0.010
7,8 ±0,25
Refer to Application Note, Document 639,
“Selecting Coupled Inductors for SEPIC Applications”
Recommended
Land Pattern
0.197
5,0
0.138
3,5
0.197
5,0
3
2
4
1
0.217
5,5
0.157
4,0
2
3
0.177
4,5
4
1
0.059
1,5
0.079
2,0
Dimensions are in
inches
mm
1
L1
3
2
L2
4
Core material
Ferrite
Terminations
RoHS compliant matte tin over nickel over phos
bronze. Other terminations available at additional cost.
Weight:
3.7 – 4.4 g
Ambient temperature
–40°C to +125°C with
Irms
current, +125°C
to +165°C with derated current
Storage temperature
Component: –40°C to +165°C.
Packaging: –40°C to +80°C
Winding to winding isolation
500 Vrms
Resistance to soldering heat
Max three 40 second reflows at
+260°C, parts cooled to room temperature between cycles
Moisture Sensitivity Level (MSL)
1 (unlimited floor life at <30°C /
85% relative humidity)
Failures in Time (FIT) / Mean Time Between Failures (MTBF)
38 per billion hours / 26,315,789 hours, calculated per Telcordia SR-332
Packaging
500/13″ reel; Plastic tape: 24 mm wide, 0.4 mm thick,
16 mm pocket spacing, 8.1 mm pocket depth
PCB washing
Only pure water or alcohol recommended
Specifications subject to change without notice.
Please check our website for latest information.
Document 704-1
Revised 08/31/09
© Coilcraft, Inc. 2010
Document 704-2
High Temperature Coupled Inductors for SEPIC – MSD1278T
Irms
(A)
Inductance
2
Part number
1
MSD1278T-472ML_
MSD1278T-562ML_
MSD1278T-682ML_
MSD1278T-822ML_
MSD1278T-103ML_
MSD1278T-123ML_
MSD1278T-153ML_
MSD1278T-183ML_
MSD1278T-223ML_
MSD1278T-273ML_
MSD1278T-333ML_
MSD1278T-393ML_
MSD1278T-473ML_
MSD1278T-563ML_
MSD1278T-683ML_
MSD1278T-823ML_
MSD1278T-104ML_
MSD1278T-124KL_
MSD1278T-154KL_
MSD1278T-184KL_
MSD1278T-224KL_
MSD1278T-274KL_
MSD1278T-334KL_
MSD1278T-394KL_
MSD1278T-474KL_
MSD1278T-564KL_
MSD1278T-684KL_
MSD1278T-824KL_
MSD1278T-105KL_
(µH)
4.7 ±20%
5.6 ±20%
6.8 ±20%
8.2 ±20%
10 ±20%
12
15
18
22
27
33
39
47
56
68
82
100
120
150
180
220
270
330
390
470
560
680
820
1000
±20%
±20%
±20%
±20%
±20%
±20%
±20%
±20%
±20%
±20%
±20%
±20%
±10%
±10%
±10%
±10%
±10%
±10%
±10%
±10%
±10%
±10%
±10%
±10%
DCR max
3
(Ohms)
0.040
0.046
0.048
0.055
0.058
0.062
0.072
0.080
0.096
0.120
0.150
0.161
0.180
0.190
0.210
0.280
0.300
0.410
0.460
0.510
0.690
0.900
1.02
1.12
1.53
1.69
2.29
2.55
2.87
SRF typ
4
(MHz)
33.0
30.0
23.0
20.0
17.0
15.0
13.0
12.0
11.0
10.0
9.5
8.5
7.5
7.0
6.5
5.0
4.5
4.3
4.1
4.0
3.4
3.1
2.9
2.7
2.2
2.0
1.7
1.4
1.3
10% drop
13.90
13.38
12.10
10.30
8.80
8.20
7.40
6.50
6.00
5.80
5.50
4.70
3.70
3.60
3.50
3.30
2.80
2.60
2.20
2.10
1.90
1.70
1.50
1.40
1.30
1.20
1.00
0.900
0.850
Isat
(A)
5
20% drop
15.20
14.86
13.56
11.52
10.00
9.18
8.36
7.38
6.80
6.56
6.10
5.26
4.34
4.18
4.04
3.72
3.24
2.94
2.54
2.42
2.16
1.94
1.70
1.60
1.50
1.34
1.08
1.04
0.948
30% drop
16.36
15.74
14.20
12.20
10.66
9.74
9.03
7.86
7.26
7.02
6.52
5.60
4.60
4.50
4.32
4.02
3.46
3.16
2.70
2.58
2.28
2.10
1.84
1.70
1.60
1.46
1.22
1.18
1.05
both
windings
6
3.16
2.87
2.81
2.76
2.56
2.48
2.30
2.18
1.99
1.78
1.59
1.54
1.45
1.41
1.35
1.16
1.13
0.96
0.91
0.86
0.74
0.65
0.61
0.58
0.50
0.47
0.41
0.39
0.37
one
winding
7
4.47
4.06
3.98
3.90
3.62
3.50
3.25
3.08
2.81
2.52
2.25
2.18
2.05
2.00
1.90
1.65
1.59
1.36
1.29
1.22
1.05
0.92
0.86
0.82
0.70
0.67
0.58
0.55
0.52
1. When ordering, please specify
termination
and
packaging
code:
MSD1278T-105KLD
Termination: L
= RoHS compliant matte tin over nickel over phos bronze
Special order:
T
= RoHS tin-silver-copper (95.5/4/0.5) or
S
= non-RoHS tin-lead (63/37).
Packaging: D
= 13″ machine-ready reel. EIA-481 embossed plastic
tape (500 parts per full reel).
B
= Less than full reel. In tape, but not machine ready.
To have a leader and trailer added ($25 charge), use
code letter D instead.
2. Inductance shown for each winding, measured at 100 kHz, 0.1 Vrms, 0
Adc on an Agilent/HP 4284A LCR meter or equivalent. When leads are
connected in parallel, inductance is the same value. When leads are
connected in series, inductance is four times the value.
3. DCR is for each winding. When leads are connected in parallel, DCR is
half the value. When leads are connected in series, DCR is twice the
value.
4. SRF measured using an Agilent/HP 4191A or equivalent. When leads
are connected in parallel, SRF is the same value.
5. DC current, at which the inductance drops the specified amount from its
value without current. It is the sum of the current flowing in both
windings.
6. Equal current when applied to each winding simultaneously that causes
a 40°C temperature rise from 25°C ambient. See temperature rise
calculation.
7. Maximum current when applied to one winding that causes a 40°C
temperature rise from 25°C ambient. See temperature rise calculation.
8. Electrical specifications at 25°C.
Refer to Doc 639 “Selecting Coupled Inductors for SEPIC Applications.”
Refer to Doc 362 “Soldering Surface Mount Components” before soldering.
Temperature rise calculation based on specified
Irms
Winding power loss = (
I
L12
+
I
L22
) × DCR in Watts (W)
52.6°C
Temperature rise (
Δ
t) = Winding power loss ×
W
52.6°C
Δt
= (
I
L12
+
I
L22
) × DCR ×
W
Example 1.
MSD1278T-153ML (Equal current in each winding)
Winding power loss = (2.3
2
+ 2.3
2
) × 0.072 = 0.761 W
52.6°C
= 40°C
Δ
t = 0.761 W ×
W
Example 2.
MSD1278T-153ML (
I
L1
= 2.4 A,
I
L2
= 1.3 A)
Winding power loss = (2.4
2
+ 1.3
2
) × 0.072 = 0.536 W
Δ
t = 0.536 W ×
52.6°C
= 28.2°C
W
Coupled Inductor Core and Winding Loss Calculator
This web-based utility allows you to enter frequency, peak-to-peak (ripple)
current, and
Irms
current to predict temperature rise and overall losses,
including core loss. Visit www.coilcraft.com/coupledloss.
Specifications subject to change without notice.
Please check our website for latest information.
Document 704-2
Revised 08/31/09
© Coilcraft, Inc. 2010
Document 704-3
High Temperature Coupled Inductors for SEPIC – MSD1278T
Typical L vs Current
10000
Typical L vs Frequency
10000
1000
1000 µH
470 µH
1000
1000 µH
470 µH
Inductance (µH)
100
100 µH
47 µH
Inductance (µH)
100
100 µH
47 µH
10
10 µH
4.7 µH
10
10 µH
4.7 µH
1
0.1
1
10
100
1
0.01
0.1
1
10
Current (A)
Frequency (MHz)
Current Derating
120
110
100
90
80
70
60
50
40
30
20
10
0
-40 -20
Percent of rated Current
Isat
Irms
0
20
40
60
80
100
120
140
160 180
Ambient temperature (°C)
25°C
Specifications subject to change without notice.
Please check our website for latest information.
Document 704-3
Revised 08/31/09
© Coilcraft, Inc. 2010
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