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
ModelS
dual
±5
±12
±15
• transient protection
- Single and dual: 50 v for 50 ms
- triple: 80 v for 120 ms
• Fully isolated
• Fixed high frequency switching
• input voltage 16 to 40 vdC
- MHF+281r9S 20 to 32 vdC
- triple output models16 to 48 vdC
• operating temperature –55° to +125°C
VDC O
utput
Single
1.9
3.3
5
5.2
5.3
12
15
28
triPle
+5 & ±12
+5 & ±15
• inhibit and synchronization functions
• indefinite short circuit protection
• up to 84% efficiency
the MHF+ Single and dual Series™ of high frequency dC/
dC converters offers a wide input voltage range of 16 to 40
volts (MHF+281r9S, 20 to 32 volts) and up to 15 watts of
output power. the units are capable of withstanding short
term transients up to 50 volts. the converters are offered with
standard screening, “eS” screening, or fully compliant to “883”
Mil-PrF-38534 Class H screening. Standard microcircuit
drawings (SMd) are available.
DESCRIPTION
MHF+ Single and dual dC/dC ConverterS
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 4 ma must
be sunk from the inhibit pin. See Figure 3.
s
ynChronization
C
onverter
D
esign
the MHF+ 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.
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
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 an
active low of ≤0.8 V is applied to the inhibit pin. The unit is
Crane aerospace & electronics
electronics group (interpoint Brand)
PO Box 97005 • Redmond WA 98073-9705
425.882.3100 • power@crane-eg.com
www.interpoint.com
undervoltage lockout prevents the single and dual output
converters from operating below approximately 14 vdC input
voltage to keep system current levels smooth, especially during
initialization or re-start operations.
Page 1 of 23
MHF+ rev l - 20091113
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 vdC delivering 15 watts of total output
power with output voltages of +5 and ±12 or +5 and ±15 vdC.
the main output, +5 vdC, 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 2.
the phase-shifted design offers reduced input and output ripple.
to meet Mil-Std-461 requirements use an eMi filter, see Figure
5. FMH-461 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 4.
i
nhibit
F
unCtion
an open collector inhibit terminal (pin 1) provides shut-down and
start-up control. applying an active low of <0.8 v, referenced to
input common, will disable the output of the converter. When
inhibited, input current is reduced to 5 ma or less and there is no
generation of switching noise. the inhibit terminal typically sinks
3 ma when the converter is inhibited.
leaving the terminal open or pulling it high will enable the
converter. use an open collector interface for active high voltages
of up to 11 volts. (refer to Figure 2 for a connection diagram.)
an open collector interface is not required if the active high is in
excess of the open circuit voltage of the inhibit terminal (11 volts)
but less than 40 volts. See Figure 2.
s
hort
C
irCuit
P
roteCtion
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 vdC input voltage to keep
system current levels smooth, especially during initialization or
re-start operations.
MHF+ SerieS™ all ModelS
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.
o
utPut
v
oltage
o
Ptions
the MHF+ Series converters are capable of providing other
output voltage options in addition to those characterized on this
datasheet. Contact your sales representative to discuss other
output voltage options.
us P
atents
interpoint converters may use one or more of the following uS
patents 5,521,807, 5,694,303 and 5,631,822.
www.interpoint.com
Page 2 of 23
MHF+ rev l - 20091113
Crane aerospace & electronics Power solutions
MHF+ Single, dual and triple dC/dC Converters
28 VOlT inPuT – 15 WATT
OPerating COnditiOns and CharaCteristiCs
Input Voltage Range
• Single and dual models:
‣
16 to 40 vdC continuous
‣
MHF+281r9S 20 to 32 dC continuous
‣
50 v for up to 50 ms transient
‣
MHF+281r9S 35 v for up to 50 ms transient
• triple models:
‣
16 to 48 vdC continuous
‣
80 v for up to 120 ms transient
synC and inhibit
Sync In
• input frequency
‣
Single and dual models: 500 to 600 kHz
‣
triple models: 400 to 600 kHz
‣
duty cycle 40% to 60%
• active low 0.8 v max
• active high 4 v min, 5 v max
• triple models: source impedance should be <100 ohms and
the transition time should be <100 nanoseconds
• if sync is not used
‣
Single and dual models: connect to input common
‣
triple models: leave unconnected
• referenced to input common
Inhibit:
• active low (output disabled)
‣
Active low voltage ≤0.8 V max
- inhibit pin current
· Single and dual models: 4.0 ma max, 3.0 ma typ
· triple models: 5.0 ma max, 3.0 ma typ
‣
referenced to input common
• active high (output enabled)
‣
Single and dual models
- open collector or unconnected
- open pin 8.5 to 12 v, 10 v typical
‣
triple models
- open collector or unconnected
- open collector interface not required if active high is
greater than 11 v and less than 40v
- open pin voltage, 11 v typical
Output Power
• 6.65 to 15 watts depending on model
Power Dissipation (Pd)
• Single and dual models: 6 watts
• 1.9 and 3.3v single: 8 watts
• triple models: 12 watts triple
Storage Temperature Range (Case)
• -65°C to +150°C
Case Operating Temperature (T
C
)
• -55°C to +125°C full power
• -55°C to +135°C absolute
Lead Soldering Temperature (10 sec per pin)
• 300°C
Undervoltage Lockout
• Single and dual models: 14 v input typical
• triple models: 8.5 v input typical
Conversion Frequency (-55°C to +125°C T
C
)
• Free run
‣
Single and dual models: 480 kHz min, 550 kHz typ,
620 kHz max
‣
triple models: 375 kHz min, 500 kHz max
Audio Rejection
• 50 dB typical
Isolation
• 100 megohm minimum at 500 v
Current Limit
• Single and dual models: 115% of full load typical
• triple models: 130% of full load typical triple
Input to Output Capacitance
• 60 pF typical
Output Voltage Temperature Coefficient
• 100 ppm/°C typical
• 150 ppm/°C maximum
Derating Output Power/Current
• linearly from 100% at 125°C to 0% at 135°C
meChaniCal and envirOnmental
Size (maximum)
• non flanged 1.460 x 1.130 x 0.330 (37.08 x 28.70 x 8.38 mm)
• Flanged 2.005 x 1.130 x 0.330 (50.93 x 28.70 x 8.38 mm)
• See cases e1, e2, g1 and g2 for dimensions.
Weight, flanged or unflanged (maximum)
• Single and dual models: 30 grams
• triple models: 35 grams
Screening:
Standard, eS or 883 (Class H). See Screening tables 1 and 2 for
more information.
www.interpoint.com
Page 3 of 23
MHF+ rev l - 20091113
Crane aerospace & electronics Power solutions
MHF+ Single, dual and triple dC/dC Converters
28 VOlT inPuT – 15 WATT
SImPLIFIED SChEmATIC DIAgRAmS
Positive
Input
5
µH
2
µF
Positive
Output
Inhibit
PWM
Controller
I
C
FET
Driver
Limit
I
D
Ref.
Input
Common
Output
Common
F
igure
1: MHF+ S
ingle
O
utput
B
lOCk
D
iagraM
Positive
Input
0°
FEEDBACK ISOLATOR
+5 Output
PWM CM
CONTROLLER
Input
Common
Synv
Output
Common
FEEDBACK ISOLATOR
+ Aux.
Output
PWM CM
CONTROLLER
180°
–Aux.
Output
F
igure
2: MHF+ t
riple
O
utput
B
lOCk
D
iagraM
www.interpoint.com
Page 4 of 23
MHF+ rev l - 20091113
Crane aerospace & electronics Power solutions
MHF+ Single, dual and triple dC/dC Converters
28 VOlT inPuT – 15 WATT
CONNECTION DIAgRAmS
MHF+
POSITIVE INPUT
9
10 k
INHIBIT
200 pF
1
1N4148
2N3501
10 K
3.9 K
8
INPUT
COMMON
F
igure
3: i
nHiBit
i
nterFaCe
9
0.01
28V
5.1k
F
7
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
4: aC C
Oupling
OF
S
ynC
S
ignal
, t
riple
M
ODelS
1
Positive Input
Positive Output
2
Positive Input
28V
FMH-461
EMI FILTER
5
Input Common
Output Common 4
Case Ground
3
Case*
MHF+
Input Common
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
5: eMi F
ilter
C
OnneCtiOn
www.interpoint.com
Page 5 of 23
MHF+ rev l - 20091113
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