Crane Aerospace & Electronics Power Solutions
smHF single and dual dc/dc converters
28 Volt input – 15 Watt
Features
• Fully qualified to Class H or K
• -55°C to +125°C operation
• 16 to 40 VDC input
• Fully Isolated
• Rad hard optocoupler feedback
• Fixed frequency, 550 kHz typical
• Topology – Single Ended Forward
• Transient protection 50 V/120 ms
• Inhibit function
• Sync function
• Indefinite short circuit protection
• Undervoltage lockout
• Up to 82% efficiency
SIngLE
2.5
3.3
5
12
15
models
vDc
DUAL
±5
±12
±15
description
The SMHF Series™ of 28 V 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,
projection-welded metal case. Flanged and non-flanged models
are available.
the output load current and providing a constant current output
above the overload point.
H
igHer
P
ower
D
enSity
SMHF converters offer screening options to Space Prototype (O),
Class H, or Class K. Radiation tolerant to Radiation Hardness
Assurance (RHA) levels of “-” (O) or “R”, per MIL-PRF-38534.
Interpoint model numbers use an “O” in the RHA designator posi-
tion to indicate the “-” (dash) Radiation Hardness Assurance level
of MIL-PRF-38534, which is defined as “no RHA”. See “Class H
and K, MIL-PRF-38534 Screening” tables for more information.
S
creening
The SMHF Series offers a new standard of performance for small
size and high power density. At just 0.33 inch high and a total
footprint of 1.7 in
2
, this low profile package offers a total power
density of up to 30 watts per cubic inch.
L
ow
n
oiSe
, H
igH
A
uDio
r
ejection
c
onverter
D
eSign
The SMHF converter’s 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
µS recovery time. Input ripple current is typically 35 mA p-p with
output ripple voltage typically 50 mV p-p .
The SMHF 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 opto-coupler in the feed-
back control loop. The opto-coupler is radiation hardened and is
especially selected for space applications.
For the SMHF dual output models, cross regulation is maintained
by tightly coupled output magnetics. Up to 70% of the total output
power is available from either output, providing the opposite
output is simultaneously carrying 30% of the total output power.
Predictable current limit is accomplished by directly monitoring
SMHF converters provide an inhibit terminal that can be used
to disable internal switching, resulting in no output and very low
quiescent input current. The converter is inhibited when a logic
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 VDC. In the inhibit mode, a maximum of
4 mA must be sunk from the inhibit pin at 28 VDC input.
i
nHibit
F
unction
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 15
Rev D - 20070404
Crane Aerospace & Electronics Power Solutions
smHF single and dual dc/dc converters
28 Volt input – 15 Watt
A synchronization feature is included with the SMHF Series that
allows the user to match the switching frequency of the converter
to the frequency of the system clock. This 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 compatible input of the desired frequency to pin 5.
The initial transition on the sync pin should be a negative transi-
tion (i.e. from high state to low state)
S
yncHronizAtion
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 opera-
tions.
S
Hort
c
ircuit
P
rotection
SMHF 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.
Positive
Input
5
µH
2
µF
Positive
Output
I
D
Inhibit
PWM
Controller
I
C
Input
Common
Output
Common
FET
Driver
Limit
Ref.
F
igure
1: SMHF S
ingle
O
utput
- B
lOck
D
iagraM
www.craneae.com
Page 2 of 15
Rev D - 20070404
Crane Aerospace & Electronics Power Solutions
smHF single and dual dc/dc converters
28 Volt input – 15 Watt
input Voltage range
• 16 to 40 VDC continuous
• 50 V for up to 50 msec transient
power dissipation (pd)
• 8 W
output power
• up to 15 watts depending on model
lead soldering temperature (10 sec per lead)
• 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 (tc)
• 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
isolation
• 100 megohm minimum at 500 VDC
• Any pin to case, except case pin
audio rejection
• 50 dB typical
conversion Frequency (º55°c to +125°c tc)
• Free run 550 kHz typical
480 kHz min, 620 kHz max
inhibit pin Voltage (unit enabled)
• 8.5 to 12 V
undervoltage lockout
• 14 V input typical
Operating COnditiOns and CharaCteristiCs
synC and inhibit
sync in (500 to 600 kHz)
• Duty cycle 40% to 60%
• Logic low 0.8 V max
• Logic high 4.5 V min, 5 V max
• Referenced to input common
• If not used, connect to input common
inhibit ttl open collector
• Logic low (output disabled)
Logic low voltage ≤0.8 V max
Inhibit pin current 12 mA max
• Referenced to input common
• Logic high (output enabled)
Open collector or unconnected
meChaniCal and envirOnmental
size (maximum)
non flanged
1.460 x 1.130 x 0.330 (37.08 x 28.70 x 8.38 mm). See case E1 for dimensions.
Flanged
2.005 x 1.130 x 0.330 (50.93 x 28.70 x 8.38 mm). See case g1 for dimensions.
Weight (maximum)
30 grams typical
screening
Space Prototype, Class H, or Class K
Radiation tolerant to Radiation Hardness Assurance (RHA) levels of “-” (O) or “R”, per MIL-STD-38534. Interpoint model numbers use an “O” in the
RHA designator position to indicate the “-” (dash) Radiation Hardness Assurance level of MIL-PRF-38534, which is defined as “no RHA”.
See “Class H and K, MIL-PRF-38534 Screening” tables for more information.
Available configurations: OO, HO, HR, KR
www.craneae.com
Page 3 of 15
Rev D - 20070404
Crane Aerospace & Electronics Power Solutions
smHF single and dual dc/dc converters
28 Volt input – 15 Watt
pin OUt
pin
1
2
3
4
5
1
6
7
8
single Output
Inhibit
no connection
O
utput Common
P
ositive Output
Sync
C
ase ground
I
nput Common
P
ositive Input
dual Output
Inhibit
Positive Output
Output Common
negative Output
Sync
Case ground
Input Common
Positive Input
1. If Sync is not used, pin 5 should be connected directly to input common.
Dot on top of cover
indicates pin one.
1
2
3
4
5
BOTTOM VIEW
SMHF SINGLE AND DUAL
NON-FLANGED OR FLANGED
8
7
6
Dotted line outlines flanged package option.
See cases E1 and g1 for dimensions.
F
igure
2: p
in
O
ut
www.craneae.com
Page 4 of 15
Rev D - 20070404
Crane Aerospace & Electronics Power Solutions
smHF single and dual dc/dc converters
28 Volt input – 15 Watt
mOdel nUmbering key
Base Model
Input Voltage
Output Voltage
Number of Outputs
(S = single, D = dual)
Case Option
(Non-flanged case has no designator
in this position)
Screening
Radiation Level
SMHF
28 05 S F / K
R
S
tanDarD
M
icrOcircuit
D
rawing
(SMD)
smd nUmbers
SMHF S
iMilar
p
art
In PROCESS
5962-0251002HXC
5962-9213902HXC
5962-9166402HXC
5962-9160102HXC
5962-9555902HXC
5962-9214402HXC
5962-9161402HXC
SMHF282R5S/HO
SMHF283R3S/HO
SMHF2805S/HO
SMHF2812S/HO
SMHF2815S/HO
SMHF2805D/HO
SMHF2812D/HO
SMHF2815D/HO
To indicate the flanged case option change the “X” to “Z” In
the SMD number. The SMD number shown is for Class H
screening, non-flanged, and no Radiation Hardness Assurance
(RHA) level. See the SMD for the numbers for other screening
and radiation levels. For exact specifications for an SMD
product, refer to the SMD drawing. Call your Interpoint
representative for status on the SMHF SMD releases which
are “in process.” SMDs can be downloaded from:
http://www.dscc.dla.mil/programs/smcr
mOdel seleCtiOn
SMHF28
Base model
V
out
value
number of outputs
/
case option
screening
Choose one from each of the following rows
V
out
value
Number of outputs
Case option
Screening
for singles 2.5, 3.3, 5, 12, 15
for duals: 5, 12, 15
“R” = decimal point, 3R3 = 3.3VDC
S (single) or D (dual)
non-flanged, leave blank F - flanged
OO* - Space prototype, HO, HR, KR
*
Interpoint model numbers use an “O” in the RHA designator position to indicate the “-” (dash) Radiation Hardness Assurance level
of MIL-PRF-38534, which is defined as “no RHA”
www.craneae.com
Page 5 of 15
Rev D - 20070404
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