–55°C to + 85°C operation
19 to 40 VDC input
Fixed frequency, 245 kHz typical
Topology – Push-Pull Forward
50 V for up to 50 ms transient protection
Indefinite short circuit protection
Remote sense on single models
Up to 84% efficiency
+5 & ±12
+5 & ±15
Size (max.): 3.20 x 2.46 x 0.595 inches (81.3 x 62.5 x 15.11 mm)
See Section B8, case L, for dimensions.
140 grams typical
Screening: Standard or ES.See Section C2 for screening
options, see Section A5 for ordering information.
The MFW Series™ of DC/DC converters offers up to 70 watts of
power from single, dual, or triple outputs in one package. Using
hybrid thick film technology 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.
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
emergency 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.
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 base-
plate. Please refer to the heat sink requirements section for more
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 accom-
plished 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.
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
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.
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