Crane Aerospace & Electronics Power Solutions
MHF+ Single, Dual and Triple DC/DC Converters
28 VOLT INPUT – 15 WATT
F
EATURES
•
•
•
•
•
•
–55° to +125°C operation
16 to 40 VDC input (16 to 48 VDC triple)
Fully isolated
Optocoupler feedback
Fixed frequency 550 kHz typical
- 450 kHz triple models
Topology
- Single and dual: Single Ended Forward
- Triple: Current Mode Flyback
Transient protection
- Single and dual: 50 V/50 ms
- Triple: 80 V/120 ms
Inhibit and sync functions
Indefinite short circuit protection
Undervoltage lockout
Up to 84% efficiency, 28 W/in
3
-
Up to 76% efficiency triple models
•
MODELS
VDC O
UTPUT
SINGLE
DUAL
TRIPLE
3.3
±5
+5 & ±12
5
±12
+5 & ±15
5.2
±15
12
15
28
•
•
•
•
MHF+ SERIES™ SINGLE & DUAL
DC/DC CONVERTERS
The MHF+ Single and Dual Series™ of high frequency DC/DC
converters offers a wide input voltage range of 16 to 40 volts and up
to 15 watts of output power. The units are capable of withstanding
short term transients up to 50 volts. The package is a hermetically
sealed, welded metal case. Flanged and non-flanged models are
available.
H
IGHER
P
OWER
D
ENSITY
The MHF+ Series offers a new standard of performance for small
size and high power density. At just 0.33 inch high and a total foot-
print of 1.7 in
2,
this low profile package offers a total power density
of up to 28 watts per cubic inch.
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. 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.
For the MHF+ dual output models, good cross regulation is main-
tained 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.
L
OW
N
OISE
, H
IGH
A
UDIO
R
EJECTION
The MHF+ converters’ feed-forward compensation system provides
excellent dynamic response and noise rejection. Audio rejection is
typically 50 dB. Typical output voltage response for a 50% to 100%
step load transient is as low as 1.3% with a 150 msec recovery time.
Input ripple current is typically 35 mA p-p with output ripple voltage
typically 30 mV p-p .
I
NHIBIT
F
UNCTION
MHF+ converters provide an inhibit terminal that can be used to
disable internal switching, resulting in no output and very low quies-
cent input current. The converter is inhibited when a TTL compatible
low (≤0.8 – output disabled) is applied to the inhibit pin. 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 4 mA must be sunk
from the inhibit pin.
Crane Aerospace & Electronics
Electronics Group (Interpoint Brand)
PO Box 97005 • Redmond WA 98073-9705
425.882.3100 • electronics@craneae.com
www.craneae.com
Page 1 of 20
Rev K - 20060613
Crane Aerospace & Electronics Power Solutions
MHF+ Single, Dual and Triple DC/DC Converters
28 VOLT INPUT – 15 WATT
S
YNCHRONIZATION
A synchronization feature is included with the MHF+ Series that
allows the user to match the switching frequency of the converter to
the frequency of the system clock. 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 TTL compatible input
of the desired frequency to pin 5.
S
OFT
S
TART
F
EATURE
The soft-start feature provides a controlled 20 milliseconds turn-on
to minimize inrush current and reduce overshoot at initial start-up or
when inhibit is released.
S
YNCHRONIZATION
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, asyn-
chronous (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. If the sync function is
not used, the terminal should be left open.
S
HORT
C
IRCUIT
P
ROTECTION
MHF+ Series 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
Undervoltage lockout prevents the units from operating below
approximately 14 VDC input voltage to keep system current levels
smooth, especially during initialization or re-start operations.
S
HORT
C
IRCUIT
P
ROTECTION
Internal current limiting circuitry protects 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.
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.
P
ACKAGING
MHF+ Triple converters are packaged in hermetically sealed metal
cases. MHF+ Triple converters can be purchased in a flanged or
non-flanged case. The flanged option provides increased heat dissi-
pation and also provides greater stability when mechanically
secured.
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 the auxiliary output voltages. The phase-shifted design
offers a further benefit in reduced input and output ripple.
I
NHIBIT
F
UNCTION
An open collector, TTL compatible, inhibit terminal (pin 1) provides
shut-down and start-up control. Applying a logic level low (<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 logic high voltages of up to 11
volts. (Refer to Figure 2 for a connection diagram.) An open collector
interface is not required if the logic high is in excess of the open
circuit voltage of the inhibit terminal, 11 volts, but less than 40 volts.
www.craneae.com
Page 2 of 20
Rev K - 20060613
Crane Aerospace & Electronics Power Solutions
MHF+ Single, Dual and Triple DC/DC Converters
28 VOLT INPUT – 15 WATT
SIMPLIFIED SCHEMATIC DIAGRAMS
5
µH
Positive
Input
2
µF
Positive
Output
Inhibit
PWM
Controller
I
C
I
D
FET
Driver
Limit
Ref.
Input
Common
F
IGURE
2: MHF+ S
INGLE
O
UTPUT
B
LOCK
D
IAGRAM
Output
Common
POSITIVE
INPUT
0°
FEEDBACK ISOLATOR
+5 OUTPUT
PWM CM
CONTROLLER
OUTPUT
COMMON
INPUT
COMMON
FEEDBACK ISOLATOR
+ AUX.
OUTPUT
SYNC
PWM CM
CONTROLLER
180°
–AUX.
OUTPUT
F
IGURE
1: MHF+ T
RIPLE
O
UTPUT
B
LOCK
D
IAGRAM
www.craneae.com
Page 3 of 20
Rev K - 20060613
Crane Aerospace & Electronics Power Solutions
MHF+ Single, Dual and Triple DC/DC Converters
28 VOLT INPUT – 15 WATT
CONNECTION DIAGRAMS
MHF+ Triple
POSITIVE INPUT
9
10 k
INHIBIT
1
1N4148
2N3501
200 pF
10 K
3.9 K
8
INPUT
COMMON
F
IGURE
5: I
NHIBIT
I
NTERFACE
9
0.01
28V
5.1k
1
8
F
7
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
6: AC C
OUPLING OF
S
YNC
S
IGNAL
1
Positive Input
Positive Output
2
9
Positive Input
28V
FMH-461
EMI FILTER
5
Input Common
Output Common 4
3
Case*
8
MHF+ TRIPLE
Input Common
6
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
7: EMI F
ILTER
C
ONNECTION
www.craneae.com
Page 4 of 20
Rev K - 20060613
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
• 50 V for up to 50 msec transient
Triple models:
• 16 to 48 VDC continuous
• 80 V for up to 120 msec
Output Power
• 12 to 15 watts depending on model
Power Dissipation (Pd)
• 6 watts single and dual, 12 watts triple
Lead Soldering Temperature (10 sec per pin)
• 300°C
Storage Temperature Range (Case)
• –65°C to +150°C
Case Operating Temperature (Tc)
• –55°C to +125°C full power
• –55°C to +135°C absolute
Derating Output Power/Current
• Linearly from 100% at 125°C to 0% at 135°C
Output Voltage Temperature Coefficient
• 100 ppm/°C typical
• 150 ppm/°C maximum
Input to Output Capacitance
• 60 pF typical
Current Limit
• 115% of full load typical (130% typical triple)
Isolation
• 100 megohm minimum at 500 V
Audio Rejection
• 50 dB typical
Conversion Frequency (55°C to +125°C Tc)
• Free run 550 kHz typical (375 minimum, 500 kHz maximum triple)
• External sync range 480 kHz min, 620 kHz max(400 to 600 kHz triple)
Inhibit Pin Voltage (unit enabled)
• 8.5 to 12 V, 10 V typical
Undervoltage Lockout
• 14 V input typical
SYNC AND INHIBIT
Sync In (500 to 600 kHz single and dual, 400 to 600 kHz
triple)
• Duty cycle 40% to 60%
• Logic low 0.8 V max
• Logic high 4 V min, 5 V max
• If not used, connect to input common (on triple models,
leave unconnected)
• Referenced to input common
Sync Out - Referenced to input common
Inhibit: TTL Open Collector
• Logic low (output disabled)
Logic low voltage ≤0.8 V max
Inhibit pin current 4.0 mA max
(3.0 typ, 5.0 max triple models)
• Referenced to input common
Logic high (output enabled)
Open collector or unconnected (single and dual)
Unconnected or 11 to 40 V (triple)
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 (maximum)
Single and dual models: 30 grams typical
Triple models: 32 grams typical
Screening
Standard, ES or 883 (Class H). See “883, Class H, QML
Products – Element Evaluation” and “883, Class H, QML
Products – Environmental Screening” for more information.
www.craneae.com
Page 5 of 20
Rev K - 20060613
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