MHF2812SSLASH883 datasheet(2/23 Pages) INTERPOINT

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MHF+ SeRIeS™ TRIple DC-DC ConVeRTeRS

MHF+ Series™ Triple dc-dc converters provide a wide input

voltage range of 16 to 48 volts delivering 15 watts of total output

power with output voltages of +5 and ±12 or +5 and ±15 volts.

The main output, +5 volts, will supply up to 7.5 watts and the

auxiliaries will supply up to 7.5 watts of combined power. Full

power operation at -55°C to +125°C plus the ability to withstand

transients of up to 80 V for up to 120 milliseconds make these

converters an ideal choice for your high reliability systems.

Converter Design

MHF+ Triple Series of dc-dc converters incorporate dual-phase,

phase-shifted technology with a continuous flyback topology.

This design eliminates a minimum load requirement on the main

output and eliminates cross regulation effects between the main

output voltage and auxiliary output voltages. See Figure 3 on

page 4.

The phase-shifted design offers reduced input and output ripple.

To meet Mil-STd-461 requirements use an eMi filter, see

Figure 4 on page 4. FMCe-0328 is the recommended filter.

inhibit FunCtion

MHF+ converters provide an inhibit terminal that can be used to

disable internal switching, resulting in no output current and very

low quiescent input current. The converter is inhibited when the

inhibit pin is pulled low (≤0.8 V = output disabled). The unit is

enabled when the inhibit pin, which is internally connected to a

pull-up resistor, is left unconnected or is connected to an open-

collector gate. When inhibited, input current is reduced to 5 ma

or less and there is no generation of switching noise. The inhibit

terminal typically sinks 5 ma when the converter is inhibited. See

Figure 7 on page 5.

soFt start Feature

The soft-start feature provides a controlled 25 milliseconds

maximum turn-on to minimize inrush current and reduce

overshoot at initial start-up or when inhibit is released.

synChronization

To synchronize the converter’s switching frequency to a system

clock apply the clock signal to the sync terminal (pin 7). When

multiple converters are powered from a single power source,

asynchronous (free run) operation will result in lower peak

noise for common spectral peaks, but synchronous operation

will eliminate any possibility of interference frequencies in the

low audio band. Source impedance of the signal should be

less than 100 ohms and the transition time should be less than

100 nanoseconds. The capacitively coupled sync input will

synchronize on a differential signal of as low as 4 volts to as high

as 5 V. For triple output models, if the sync function is not used,

the terminal should be left open. See Figure 5 on page 4.

short CirCuit ProteCtion

On the triple output models, internal current limiting circuitry

protects on all three outputs against short circuits. When output

power exceeds approximately 130% of maximum output power,

the output currents are limited. in addition, separate current

limiting circuitry protects each output individually resulting in

normal operation of either the main or the auxiliaries, whichever

is not in a shorted condition.

unDervoltage loCkout

undervoltage lockout prevents the triple output models units from

operating below approximately 8.5 volts input voltage to keep

system current levels smooth, especially during initialization or

re-start operations.

PaCkaging

MHF+ Series of converters are packaged in hermetically sealed

metal cases and can be purchased in a flanged or non-flanged

case. The flanged option provides increased heat dissipation and

also provides greater stability when mechanically secured.

www.craneae.com/interpoint

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Crane Aerospace & Electronics Power Solutions

mHF+ Single, Dual and Triple DC-DC Converters

28 VOlT INPuT – 15 WaTT

MHF+ rev aB - 2014.10.02

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