MODELS

B2-77

Size (max.): 1.460 x 1.130 x 0.330 inches (37.08 x 28.70 x 8.38 mm)

See Section B8, case E1 for dimensions.

Weight:

21 grams typical.

Screening:

Standard or ES.

See section C2 for screening options.

SINGLE

5

12

15

DUAL

±12

±15

DESCRIPTION

The MHF Series™ of DC/DC converters offer up to 12 watts of

power from single or dual outputs in a single package over a the full

military temperature range. Thick film hybrid manufacturing tech-

nology produces high levels of miniaturization, giving the MHF

Series converters a low profile (0.330 inch), small board area (1.65

The parts are packaged in hermetically sealed steel enclosures,

making them ideal for use in military, aerospace, and high reliability

industrial applications.

The MHF converters are switching regulators which use a quasi-

square wave, single ended forward converter design with a nominal

switching frequency of 600 kHz. Isolation between input and output

circuits is provided with a transformer in the forward power loop and

a temperature insensitive optical link in the feedback control loop.

Output regulation is accomplished with constant frequency pulse

width modulation. Both line and load regulation are typically within

10 mV.

On dual output models, the positive output is independently regu-

lated and the negative output is cross-regulated. Figures 7 and 8

illustrate what effects load changes have on the negative output.

Indefinite short circuit protection and overload protection are

provided by sensing output load current and restricting the output

current to approximately 125% of full load output current. Since the

output current is sensed in the secondary stage, the result is a

predictable, constant output current control with no foldback char-

acteristics. MHF converters are provided with internal filtering

elements on both the input and output to help reduce the need for

external components. For information about filtering to meet MIL-

STD-461’s CE03 test, contact your Interpoint representative.

The MHF Series is designed to provide full power operation over the

input voltage range of 16 to 40 volts. The 15 volt models provide a

19 to 40 volt range. Operation below 16 volts (or 19 volts for the 15

volt models), including operation in MIL-STD-704E emergency

power conditions, is possible with derated output power. Please

refer to the low line drop-out graphs, Figures 9 and 10.

The MHF Series provides full power operation at case temperatures

from –55°C up to +125°C. All 12 and 15 volt models in both single

and dual output configurations provide full power operation at

+125°C with derated power to 135°C. The +5 volt model provides

full power at 110°C derated to 0% at 130°C. Depending on operating

levels, air flow, and ambient temperature; heat sinking may be

required.

An inhibit terminal is provided that can be used to disable internal

switching, resulting in a very low quiescent input current. An open

collector TTL compatible low (

≤0.8V) is required to control the inhibit

function. This level may be supplied by an open collector gate since

the inhibit pin is provided with an internal pull-up resistor.

MHF SERIES

12 WATT

• –55° to +125°C operation

• 16 to 40 VDC input

(19 to 40 VDC for 15 volt outputs)

• Fully Isolated

• Optocoupler feedback

• Fixed frequency 600 kHz typical

• Forward converter topology

• 50 V for up to 50 ms transient protection

• Inhibit function

• Indefinite short circuit protection