Crane Aerospace & Electronics Power Solutions
mHF+ Single, Dual and Triple DC-DC Converters
28 VOlT INPuT – 15 WaTT
FEaTuRES
Only 0.33 inches (8.38 mm) high in a
hermetically sealed case
• Input voltage 16 to 40 Volts
•
Operating temperature –55° to +125°C
-
MHF+281R9S 20 to 32 Volts
- Triple output models 16 to 48 Volts
1.9
3.3
5
5.2
5.3
12
15
28
O
utput
V
Oltage
(V)
mODElS
dual
±5
±12
±15
Single
TriPle
+5 & ±12
+5 & ±15
•
Transient protection
- Single and dual: 50 V for 50 ms
- MHF+281R9S: 35 V for 50 ms
- Triple: 80 V for 120 ms
• Fixed high frequency switching
•
Fully isolated
•
inhibit and synchronization functions
•
indefinite short circuit protection
•
under voltage lockout
DESCRIPTION
MHF+ SerieS™ SingleS and dualS
interpoint® MHF+ Series singles and duals are high frequency
dc-dc converters offering a wide input voltage range of 16 to 40
volts (MHF+281r9S, 20 to 32 volts) and up to 15 watts of output
power. Transient protection up to 50 volts for up to 50 ms. The
converters are offered with standard screening, “eS” screening,
or fully compliant to “883” Mil-PrF-38534 Class H screening
(see Table 13 on page 23). Standard Microcircuit drawings
(SMd) are available (see Table 3 on page 7.
The unit is enabled when the pin, which is internally connected to
a pull-up resistor, is left unconnected or is connected to an open-
collector gate. The open circuit output voltage associated with the
inhibit pin is 8.5 to 12 V. In the inhibit mode, a maximum of 5 mA
must be sunk from the inhibit pin. See Figure 6 on page 5
s
ynChronization
C
onverter
D
esign
The MHF+ Series single and dual converters are switching
regulators that use a quasi-square wave, single-ended forward
converter design with a constant switching frequency of 550 kHz
typical. isolation between input and output circuits is provided
with a transformer in the forward path and a temperature
compensated optical link in the feedback control loop. See
Figure 1 and Figure 3 on page 4
For the MHF+ dual output models, good cross regulation is
maintained by tightly coupled output magnetics. up to 90%
of the total output power (80% on 2805d) is available from
either output, providing the opposite output is simultaneously
carrying 10% of the total output power (20% on 2805d models).
Predictable current limit is accomplished by directly monitoring
the output load current and providing a constant current output
above the overload point.
An external synchronization feature is included that allows the
user to adjust the nominally 550 kHz operating frequency to
any frequency within the range of 500 kHz to 600 kHz. This is
initiated by applying a signal input of the desired frequency to
pin 5. The capacitively coupled sync input will synchronize on a
differential signal of as low as 4 volts to as high as 5 V. For single
and dual output models, if the sync function is not used, connect
the terminal to input common.
s
hort
C
irCuit
P
roteCtion
MHF+ Series single and dual output converters provide short
circuit protection by restricting the output current to approximately
115% of the full load output current. The output current is sensed
in the secondary stage to provide highly predictable and accurate
current limiting, and to eliminate foldback characteristics.
u
nDervoltage
l
oCkout
i
nhibit
F
unCtion
undervoltage lockout prevents the single and dual output
converters from operating below approximately 14 Volts input
voltage to keep system current levels smooth, especially during
initialization or re-start operations.
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).
Crane Aerospace & Electronics
Power Solutions - Interpoint Products
10301 Willows Road NE, Redmond, WA, 98052
+1.425.882.3100 • power@crane-eg.com
www.craneae.com/interpoint
P
aCkaging
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.
MHF+ rev aB - 2014.10.02
Page 1 of 23
Crane Aerospace & Electronics Power Solutions
mHF+ Single, Dual and Triple DC-DC Converters
28 VOlT INPuT – 15 WaTT
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.
s
oFt
s
tart
F
eature
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.
s
ynChronization
C
onverter
D
esign
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.
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.
s
hort
C
irCuit
P
roteCtion
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.
i
nhibit
F
unCtion
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.
u
nDervoltage
l
oCkout
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.
P
aCkaging
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
Page 2 of 23
MHF+ rev aB - 2014.10.02
Crane Aerospace & Electronics Power Solutions
mHF+ Single, Dual and Triple DC-DC Converters
28 VOlT INPuT – 15 WaTT
Positive
Input
5
μH
Regulator
2
μF
Positive
Output
I
D
Inhibit
PWM
Controller
I
C
Input
Common
Output
Common
FET
Driver
Limit
Ref.
F
igure
1: MhF+ s
ingle
o
utPut
b
loCk
D
iagraM
Positive
Input
5 µH
Regulator
L2A
2 µF
Positive
Output
I
D
Inhibit
PWM
Controller
I
C
Input
Common
FET
Driver
R
S
Limit
Ref.
R
S
L2B
Output
Common
Negative
Output
F
igure
2: MhF+ D
ual
o
utPut
b
loCk
D
iagraM
www.craneae.com/interpoint
Page 3 of 23
MHF+ rev aB - 2014.10.02
Crane Aerospace & Electronics Power Solutions
mHF+ Single, Dual and Triple DC-DC Converters
28 VOlT INPuT – 15 WaTT
Positive
Input
0°
FEEDBACK ISOLATOR
+5 Output
PWM CM
CONTROLLER
Input
Common
Sync
Output
Common
FEEDBACK ISOLATOR
+ Aux.
Output
PWM CM
CONTROLLER
180°
–Aux.
Output
F
igure
3: MhF+ t
riPle
o
utPut
b
loCk
D
iagraM
1
Positive Input
Positive Output
2
Positive Input
28V
FMCE-0328
EMI FILTER
5
Input Common
Output Common 4
Case Ground
3
Case*
Input Common
MHF+
Case Ground
Chassis Ground
*The case ground connection should be as low an impedance as possible to minimize EMI.
Direct contact of baseplate to chassis ground provides the lowest impedance.
F
igure
4: eMi F
ilter
C
onneCtion
9
28V
0.01 µF
7
5.1k
1
8
Positive Input
Sync In
Inhibit
Input Common
+5 Output 2
+ Aux. Output 4
Output Common 3
– Aux. Output 5
– Aux.
Load
+ Aux.
Load
+5
Load
if the sync terminal (pin 7) is not used, it must be left floating.
The ac coupling shown will prevent sync signal failure.
F
igure
5: aC C
ouPling oF
s
ynC
s
ignal
, t
riPle
M
oDels
www.craneae.com/interpoint
Page 4 of 23
MHF+ rev aB - 2014.10.02
Crane Aerospace & Electronics Power Solutions
mHF+ Single, Dual and Triple DC-DC Converters
28 VOlT INPuT – 15 WaTT
POSITIVE INPUT
5 kΩ
10 kΩ
INHIBIT
1 kΩ
PRIMARY
BIAS
10 V
INPUT
COMMON
F
igure
6: i
nhibit
i
nterFaCe
s
ingles anD
D
uals
POSITIVE INPUT
10 kΩ
INHIBIT
10 V
PRIMARY
BIAS
INPUT
COMMON
F
igure
7: i
nhibit
i
nterFaCe
t
riPles
www.craneae.com/interpoint
Page 5 of 23
MHF+ rev aB - 2014.10.02
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