MODELS
VDC OUTPUT
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
square inches), and high power density (22 watt/in3).
The parts are packaged in hermetically sealed steel enclosures,
making them ideal for use in military, aerospace, and high reliability
industrial applications.
DESIGN METHODOLOGY
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.
WIDE VOLTAGE RANGE
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.
MILITARY TEMPERATURE RANGE
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 1 10°C derated to 0% at 130°C. Depending on operating
levels, air flow, and ambient temperature; heat sinking may be
required.
INHIBIT FEATURE
An inhibit terminal is provided that can be used to disable internal
switching, resulting in a very low quiescent input current. An open
collector TTLcompatible 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.
DC/DC C
ONVERTERS
28 V
OLT
I
NPUT
MHF SERIES
12 WATT
FEATURES
• –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
• Up to 83% efficiency, 22 W/in3