B4-3

MFW SERIES

70 WATTS

MODELS

SINGLE

5

12

15

DUAL

±12

±15

TRIPLE

+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.

Weight:

140 grams typical

Screening:

Standard or ES.See Section C2 for screening

options, see Section A5 for ordering information.

DESCRIPTION

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.

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.

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.

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

information.

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.

• –55°C to + 85°C operation

• 19 to 40 VDC input

• Fully Isolated

• Optocoupler feedback

• Fixed frequency, 245 kHz typical

• Topology – Push-Pull Forward

• 50 V for up to 50 ms transient protection

• Inhibit/sync function

• Indefinite short circuit protection

• Remote sense on single models

• Up to 84% efficiency