NOT RECOMMENDED FOR NEW DESIGNS
Features
DC/DC C
OnVERtERs
28 V
Olt
I
nput
mFw SeRIeS
70 WATT
• –55°C to + 85°C operation
• 19 to 40 VDC input
• Fully isolated
• 50 V for 50 ms transient protection
• Fixed frequency switching
• Inhibit/sync function
modELS
VDC O
utput
Dual
• Remote sense on single models
±12
±15
tRIplE
+5 & ±12
+5 & ±15
• Up to 84% efficiency
• Indefinite short circuit protection
Size (max.): 3.20 x 2.46 x 0.595 inches (81.3 x 62.5 x 15.11 mm)
See case L for dimensions.
Weight:
140 grams typical
Screening: Standard or ES. See screening table for more information.
description
The mFW Series™ of dC/dC converters offers up to 70 watts of power
from dual or triple outputs in one package. Using hybrid thick film tech-
nology a power density of over 20 watts per cubic inch is achieved.
These devices are packaged in hermetically sealed cold rolled steel
enclosures with a tin plate finish making them ideal for use in military,
aerospace, or other high reliability applications. Unscreened models
are guaranteed to pass a gross leak test (maximum leak rate of 0.001
atm-cc/sec). Environmentally screened units (designated by the /ES
suffix) are hermetically solder sealed. See Section C2 for screening
specifications.
w
IDE
V
OltagE
R
angE
All models of the mFW Series are designed to provide full power
operation over an input voltage range of 19 to 40 VdC. operation
below an input of 19 volts, including operation in mIL-STd-704E emer-
gency power conditions, is possible with derated output power. Please
refer to the derating information and the low voltage drop-out graphs
(Figures 10 and 11) on the following pages.
w
IDE
t
EMpERatuRE
R
angE
D
EsIgn
M
EthODOlOgy
The mFW Series converters utilize a quasi-square wave forward
converter design with a nominal switching frequency of 245 kHz.
Isolation between input and output is provided with a transformer in the
forward power loop and a wideband, temperature insensitive optical
link in the feedback control loop. output regulation is accomplished
with constant frequency pulse width modulation. In addition, the load
regulation of the single output models is further enhanced through
the use of remote output voltage sense pins to overcome the adverse
effects of line resistance voltage drops. Short circuit protection is
provided by detecting peak primary switching current on a cycle by
cycle basis and limiting it to approximately 130% of the full load input
current. This method results in quick and positive current limiting under
short circuit conditions.
Full load operation of any of the mFW Series converters is available
at case temperatures of –55°C to + 85°C. operation up to +125°C is
possible with derated output power. The mFW Series converters are
provided in a flange mount case designed to facilitate the removal of
internally generated heat. Because of this, heat sinking requirements
are minimal. Sustained full power operation does however require that
an efficient heat sink be attached to the baseplate. Please refer to the
heat sink requirements section for more information.
I
nhIbIt
/s
ynC
F
EatuRE
l
Ow
n
OIsE
Standard on all models of the mFW Series is a dual mode inhibit/sync
pin. This pin serves as both an output inhibit and as a synchronization
input. In the inhibit mode an open collector TTL compatible low (<0.8
V) will disable internal switching thereby inhibiting the unit’s output.
Inhibiting in this manner results in an extremely low quiescent current.
Since a pull-up resistor is included internally, this pin may be left open
should the inhibit function not be desired.
In a digital system it is often desirable to synchronize the input or
output ripple with the system clock. For this reason each model of the
mFW Series was designed to synchronize with a system clock applied
to the inhibit/sync pin. Please refer to the technical data section for
timing details for the external sync feature.
The mFW Series converters offer low noise on both the input and
output lines. A two section, four pole LC input filter is included to
provide very low reflected line ripple current. Adherence to mIL-STd-
461C (CE03) is possible with the addition of the FmB-461 filter. output
ripple is maintained at less than 50 mV p-p for single and dual output
models and 85 mV for triple output models.
Crane Aerospace & Electronics
Electronics Group (Interpoint Brand)
PO Box 97005 • Redmond wA 98073-9705
425.882.3100 • power@crane-eg.com
www.interpoint.com
Page 1 of 7
mFw Rev F 20100212
DC/DC C
OnVERtERs
absOlute maximum ratings
output power
• 60 to 70 watts depending on model
Lead soldering temperature (10 sec per lead)
• 300°C
storage temperature range (case)
• –55°C to +125°C
mFw SeRIeS
70 WATT
sync and inhibit
recOmmended Operating cOnditiOns
input Voltage range
• 19 to 40 VDC continuous (see Derating)
case operating temperature (tc)
• –40°C to +85°C full power
sync in (245 to 370 kHz.)
• Duty cycle 70% min, 98% max.
• Logic low 0.8V max
• Logic high 4.5 V min
• Referenced to input common
• If sync is not used, leave unconnected
inhibit ttL open collector
• Logic low (output disabled)
Inhibit pin current 1 mA max
• Referenced to input common
• Logic high (output enabled)
V = ≥ 4.5V
derating Output pOwer/current and input vOltage
typical characteristics
temperatures are referenced to the temperature at the converter’s base-
plate
• Linearly derate output power/current from 100% at 85°C to 0% at 125°C.
• Above 105°C linearly derate steady state input voltage to 33 volts at 125°C.
• Indefinite short circuit protection is not guaranteed above 85°C case.
• Operation below an input voltage of 19 volts, including operation in mIL-
STd-704E emergency power conditions, is possible with derated output
power. See Figures 10 and 11.
output Voltage temperature coefficient
• 150 ppm/°C, typical
input to output capacitance
• 160 pF, typical
isolation
• 100 megohm minimum at 500 V
conversion Frequency
• Free run mode 245 kHz, typical
inhibit pin Voltage (unit enabled)
• 4.5 to 5.5 V
www.interpoint.com
Page 2 of 7
mFw Rev F 20100212
DC/DC C
OnVERtERs
DUAL AnD tRIPLe OUtPUt mODeLS
paRaMEtER
Output VOltagE
mFw SeRIeS
70 WATT
Electrical Characteristics: 25°C Tc, 28 VdC Vin, 100% load, free run, unless otherwise specified.
mFW2812d
MIn
—
—
—
—
—
—
MaIn
Dual
MaIn
Dual
MaIn
Dual
mFW2815d
MIn
typ
—
—
2.33
—
35
—
—
30
—
10
—
25
1.5
2.0
MaX MIn
— 4.95
—
—
66.5
70
—
—
—
—
—
—
—
—
—
—
— —
—
5.5
—
—
—
—
—
—
—
—
—
mFW2812T
typ
5.05
4.0
1.67
20
20
—
50
50
2
100
5
480
—
—
MaX MIn
5.10 4.90
10.0
50
50
60
85
85
20
200
20
600
—
—
—
—
—
—
—
—
—
—
mFW2815T
typ
4.95
4.0
1.33
20
20
—
50
50
2
100
5
300
—
—
MaX
5.05
10.0
3.33
50
50
60
85
85
20
200
20
450
—
—
COnDItIOns
Full
lOaD
V
In
=
19
tO
40
MaIn
MaIn
Dual
MaIn
Dual
typ
—
—
2.92
—
35
—
—
30
—
10
—
25
1.5
2.0
MaX
unIts
VdC
A
±11.88 ±12 ±12.12
±14.85 ±15 ±15.15
±11.65 ±11.80 ±12.05
±15.05 ±15.30 ±15.55
Output
CuRREnt1,2
Output pOwER1,2
4.4
—
4.2
—
±
Dual
tOtal
Output RIpplE
Full lOaD
bw
≤
2 mHz
66.5
70
—
—
—
W
—
—
—
—
—
—
—
—
50 —
25 —
50 —
3.0 —
4.0 —
50 —
25 —
50 —
3.0 —
3.5 —
mV p-p
mV
mV
lInE REgulatIOn
lOaD REgulatIOn3
V
In
=
19
tO
40
nO lOaD
tO Full
CROss
REgulatIOn4
Dual
+
p
O
= 3
w tO
35
w
-
p
O
= 35
w
— —
— —
%
CROss
REgulatIOn5
MaIn
+
p
O
= 33
w
Dual
+
p
O
= 3
w tO
27
w
-
p
O
= 27
w tO
3
w
+
p
O
= 20
w tO
50
w
-
p
O
= 50
w tO
20
w
—
—
19
—
—
—
80
—
—
—
28
75
30
15
83
15
—
—
40
—
—
19
—
—
28
75
30
15
83
15
—
—
40
35
—
—
19
—
2.3
5.4
28
60
30
15
84
6
6.0
9.0
—
—
2.3
5.0
28
60
30
15
84
6
5.0
7.0
40
110
35
40
—
10
%
MaIn
+
pO
= 3
w tO
30
w
Dual
±
p
O
= 15
w
nO lOaD
InhIbItED
Input VOltagE
Input CuRREnt
40 19
110 —
35
40
—
—
—
80
VdC
mA
mA p-p
%
ms
90 —
35 —
40 —
— 80
25
—
90 —
Input RIpplE
CuRREnt
EFFICIEnCy
staRtup DElay
Full lOaD
bw
≤ 10
mHz
40 —
— 80
25 —
10 —
Notes
1. on dual output models the maximum combined output power is 70 watts.
A maximum of 95% (66.5 W) is available from any single output.
2. on triple output models the maximum combined output power is 60 watts.
A maximum of 50 watts is available from a single output.
3. Balanced loads
4. egulation effect on the negative dual output during the defined
R
conditions.
5. egulation effect on both dual outputs during the defined conditions.
R
www.interpoint.com
Page 3 of 7
mFw Rev F 20100212
DC/DC C
OnVERtERs
The mFW Series of dC/dC converters has an upper operating
temperature of + 85°C at the baseplate of the case. The degree of
heat sinking required to remain within this limit may be determined
from Figure 1 which shows the maximum allowed internal power dissi-
pation (P
dISS
vs. ambient temperature for various heat sink thermal
resistances. P
dISS
may be calculated as:
P
dISS
= P
oUT
/ efficiency – P
oUT
The efficiency for all combinations of PoUT and VIN for the various
models may be obtained from the graphs on the preceding pages.
Example: Converter = mFW2815d, T
AmB
= 70°C,
V
IN
= 28 VdC, P
oUT
= 45 watts
Efficiency = 85% (From Figure 7)
P
dISS
= (45 / 85) – 45 = 7.95 watts
From Figure 1 we can see that this situation will require thermal resis-
tance of approximately 4.5°C / watt.
Conversely we may also find the maximum ambient temperature
which can be tolerated if we know the heat sink thermal resistance.
Example: Converter = mFW2805S, VIN = 28 VdC, P
oUT
= 45 W.
thermal Resistance = 3°C / watt.
Efficiency = 83.5% (From Figure 3)
P
dISS
= (45 / 0.835) – 45 = 8.89 watts.
mFw SeRIeS
70 WATT
tHermaL management
C
alCulatIng
M
aXIMuM
a
MbIEnt
t
EMpERatuRE
From Figure 1 we can see that the maximum allowed ambient temper-
ature is approximately 75°C.
h
Eat
s
Ink
R
ECOMMEnDatIOns
An mFW Series converter in still air (other than convective currents)
and with no conductive cooling paths other than through electrical
connections at the pins will exhibit a thermal resistance of approxi-
mately 4°C / watt. In cases where this value proves to be too high it is
recommended that additional heat sinking be supplied. The simplest
method of accomplishing this is to firmly attach the converter to a PCB
thereby providing a conductive thermal path. Secondly it is recom-
mended that airflow be provided over the converter. Although each
situation requires a thorough thermal analysis these two measures
can reduce the thermal resistance to as low as 2°C / watt. If calcula-
tions indicate further heat sinking is required it is recommended that
additional thermal mass be provided either under the base plate or on
top of the converter’s mounting flanges or both.
pin Out
20
W
/W /W /W C/
°
C
°
C 2
°
C 0
°
=4 U=3 U= U=
U
15
10
5
pin dual Output
1
Positive Input
2
Case Ground
3
Input Common
4
Inhibit/Sync In
5
Negative output
6
Positive output
7, 8 output Common
9, 10 No Connection
triple Output
Positive Input
Case Ground
Input Common
Inhibit/Sync In
Neg. Aux. output
Positive Aux. output
output Common
main (+5) output
Watts
Squared corner indicates pin one.
20° 40° 60° 80° 100° 120° 140°
Degrees Centigrade
Internal Power Dissipation (max)
vs. Ambient Temperature
F
IGuRE
1
1
2
3
4
BOTTOM VIEW
MFW
See case L for dimensions.
9
7
5
10
8
6
F
IGuRE
2: P
IN
O
uT
www.interpoint.com
Page 4 of 7
mFw Rev F 20100212
DC/DC C
OnVERtERs
mFw SeRIeS
70 WATT
Typical Performance Curves: 25°C Tc , 28 VdC Vin, 100% load, free run, unless otherwise specified.
87
85
19 V
87
85
19 V
87
19 V
85
83
Efficiency (%)
Efficiency (%)
83
81
79
77
75
73
71
10
40 V
28 V
83
Efficiency (%)
81
79
77
75
73
71
40 V
28 V
81
79
77
75
73
71
40 V
10
20
30
40
50
60
70
28 V
MFW2812D Efficiency vs Line & Load
Output Power (Watts)
20
30
40
50
60
70
10
F
IguRE
3
MFW2815D Efficiency vs Line & Load
Output Power (Watts)
20
30
40
50
60
70
F
IguRE
4
MFW28512T Efficiency vs Line & Load
Output Power (Watts)
F
IguRE
5
19
87
85
19 V
18
MFW2815D
MFW2812D
2815S
Input Voltage (Volts)
Input Voltage (Volts)
83
283R5S
17
18
Efficiency (%)
81
79
77
75
73
71
10
40 V
28 V
16
2812S
2805S
17
16
MFW28512T
MFW28515T
15
15
MFW28515T Efficiency vs Line & Load
Output Power (Watts)
20
30
40
50
60
70
10
20
30
40
50
60
70
10
Low Line Dropout vs. Load (50 mV drop)
MFW Single Output Models
Output Power (Watts)
Low Line Dropout vs. Load (50 mV drop)
MFW Dual and Triple Output Models
Output Power (Watts)
20
30
40
50
60
70
F
IguRE
6
F
IguRE
7
F
IguRE
8
mOdel numbering key
Base Model
Input Voltage
MFW
28 512 T / ES
Output Voltage
(Main and Aux. Vout for triple models)
Number of Outputs
(D = dual, T = triple)
Screening
(Standard screening has no designator
in this position.)
www.interpoint.com
Page 5 of 7
mFw Rev F 20100212
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