Crane Aerospace & Electronics Power Solutions
sMrt28 single, Dual and triple space Dc/Dc converters
28 VOLt Input – 35 Watt – space quaLIFIeD
Features
Built in MIL-stD-461 eMI filter
• Operating temperature -55° to +125°C
Output trim from 51% to 124% of nominal
• Qualified to MIL-PRF-38534 Class H and K
• Radiation hardness assurance (RHA) to
level F 300 kRad(Si)
• Input voltage range 19 to 56 VDC
• Fully isolated, 5 port isolation
• Dual magnetic feedback
• Remote sense
• Transient protection 80 V for 120 ms
• Fixed high frequency switching
• Inhibit function
• Synchronization input
• Radiation tolerant to
• Indefinite short circuit protection
- 1 x 10
12
protons/cm
2
neutron or proton fluence
- 3 x 10
5
rad(Si) total dose
- 10
11
rad(Si)/sec dose rate
VDC O
utput
SIngLE
3.3
5
8.7
12
15
DUAL
±5
±12
±15
MODELS
• Meets MIL-STD-704A transient standards
- SEE - LET to 80 MeV cm
2
/mg
TRIPLE
+3.3 & ±12
+3.3 & ±15
+5 & ±7
+5 & ±12
+5 & ±15
DescrIptIOn
The SMRT28 Series™ of DC/DC converters offers up to 35
watts of power in a radiation tolerant design. The low profile
SMRT28 converters are manufactured in Interpoint’s fully
certified and qualified MIL-PRF-38534 production facility and
packaged in hermetically sealed steel cases. They are ideal for
use in programs requiring high reliability, small size, and high
levels of radiation hardening assurance.
The SMRT28 converters are switching regulators which use a
two-phase, phase shifted flyback design with a nominal switching
frequency of 300 kHz. Close regulation is maintained with
advanced constant frequency pulse width modulation design
techniques. The SMRT28’s feed-forward compensation and
discontinuous topologies provide high levels (80 dB peak) of
input-to-output ripple rejection.
Two independent feedback loops are used to regulate the dual
and triple outputs, one feedback loop regulates the two-phased
single output. Each set of outputs is electrically isolated from the
other and from the input. This product configuration eliminates
cross regulation effects between output sets.
Configurations:
• Single Output: One two-phase single output
• Dual Output: Two single-phase single outputs
• Triple Output: One single-phase independent
Main output and one single-phase dual output.
(± Auxiliary output)
Crane Aerospace & Electronics
Crane Electronics, Inc.
Power Solutions – Interpoint
PO Box 97005 • Redmond WA 98073-9705
425.882.3100 • power@crane-eg.com
www.craneae.com/interpoint
Cleared by the U.S. Department of Defense (DoD) Office of Security Review (OSR)
for public release. OSR case number 11-S-0729, dated January 4, 2011.
SMRT28 Rev F - 2011.01.24
Page 1 of 22
Crane Aerospace & Electronics Power Solutions
sMrt28 single, Dual and triple space Dc/Dc converters
28 VOLt Input – 35 Watt – space quaLIFIeD
u
nDerVOltage
l
OCkOut
The converters have an undervoltage lockout that will allow
power conversion at approximately 17 volts on a rising input
voltage and a conversion shut-down on a falling voltage at
approximately 14.5 volts.
The SMRT28 Series incorporates an inhibit terminal that can
be used to disable internal switching. It is not recommended
to tie the Inhibit pin of an SMRT28 directly to the Inhibit pin of
another converter as the SMRT28 Inhibit pin can sink current.
When pulling multiple inhibit signals low a separate interface
is recommended for each SMRT28. The converter is inhibited
when the inhibit pin is pulled low (0.4 V). In the inhibit mode the
inhibit pin current requirement is less than ~2 mA. The converter
resumes normal operation when a high (≥ 2.4 V) signal or open
circuit is applied to the inhibit pin. The open circuit voltage of
the inhibit is 5 to 6 volts. Although open circuit is the preferred
method for the enabled state, up to 10 volts may be applied to
the inhibit pin.
At the highest dose rate (10
11
rad(Si)/sec dose rate) there will be
an upset resulting in a dip in the voltage. This is non-destructive
to the unit. The converter will operate through the upset.
S
CreenIng
I
nhIbIt
F
unCtIOn
SMRT28 converters offer the following screening options:
Space Prototype (O), Class H, or Class K. Radiation tolerant to
Radiation Hardness Assurance (RHA) levels of “-” (O), “P”, “R” or
“F”, per MIL-PRF-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 Screening Tables 1, 2 and 3 for more information.
emI
The SMRT28 has a built-in EMI input filter which brings the
conducted emissions into compliance with both methods of
MIL-STD-461, revisions C-CE03 and D-/E-/F-CE102.
S
enSe
S
ynChrOnIzatIOn
The Sync Input is isolated which allows Sync Return to be tied to
the primary side, secondary side, or float with respect to all inputs
and outputs. Input current into this pin is limited by a series 1 k
ohm resistance.
Tight load regulation is maintained via wide bandwidth magnetic
feedback and through the use of remote sense on single output
models and one output (Output “A”) of the dual units. The sense
feature can be used to adjust the output voltage by connecting a
resistor between the positive sense line and the positive output.
O
utput
V
Oltage
t
rIm
The output voltage of each set can be trimmed from 51% to
125% of nominal (varies by model, see trim instructions on page
4). The following are “sets” of voltages in relation to trim:
• Triple output models: Main output is one set, the dual outputs
are another set.
• Dual outputs: Each output is a “set.”
One set can be trimmed using the trim pin, the other set can
be trimmed (up only) using the positive sense pin.
• Single: One set
The SMRT28 DC/DC converters are designed to provide
continuous normal operation through radiation levels associated
with space missions and in tactical and strategic military
environments. The converters will operate normally in radiation
environments with up to 1 x 10
12
neutrons per square centimeter
neutron fluence, 10
11
rad(Si) per second dose rate, and 3x10
5
rad(Si) total dose.
These levels of radiation tolerance make the SMRT28 converters
suitable for electronics in programs where operation in high
radiation environments is required.
(see trim tables on page 4 for more options)
S
enSe
A
djuSt
I
nStructIonS for
o
utput
A
on
d
uAl
M
odelS
A
djuSt
u
p
o
nly
R
a
DjuSt
= 240
(
Vout - Vnom
Vmax - Vout
)
r
aDIatIOn
t
OleranCe
Vout = desired output voltage
Vnom = nominal unadjusted output voltage
Vmax = maximum achievable output voltage
5V Vmax = 6.0 V
12V Vmax = 14.68 V
15V Vmax = 18.36V
note: R
ADJUST
should be connected
between Sense A (pin 8) and Vout A (pin 11).
www.craneae.com/interpoint
Page 2 of 22
SMRT28 Rev F - 2011.01.24
Crane Aerospace & Electronics Power Solutions
sMrt28 single, Dual and triple space Dc/Dc converters
28 VOLt Input – 35 Watt – space quaLIFIeD
Operating COnditiOns and CharaCteristiCs
Input Voltage range
• 19 to 56 VDC continuous
• 80 V for 120 ms transient
conversion Frequency
• 300 kHz typ 270 kHz min, 330 kHz max
Output power
• Up to 35 watts depending on model
Lead soldering temperature (10 sec per pin)
• 300°C
storage temperature range (case)
• -65°C to +150°C
radiation (will operate through)
• 1x10
12
neutrons/cm
2
neutron or proton fluence
• Radiation dose rate 10
11
rad(Si) /sec
• Total dose up to 300 kRad(Si)
• SEE - LET to 80 MeV cm
2
/mg
synC and inhibit
sync
• Input frequency 270-330 kHz
• Duty cycle 20% min, 80% max
• 2.5 V p-p minimum amplitude
• 10 V p-p maximum amplitude
• Sync circuit is floating and isolated
• If sync is used at lower end of the range, full load
operation is not guaranteed.
Inhibit
• Converter disabled (active low)
‣
InH referenced to input common
‣
Active low, pulled to 0.4 V or lower
‣
Inhibit pin current < 2 mA
• Converter enabled (active high)
‣
Active high >2.4 V
‣
not to exceed 10 V
‣
Open pin voltage 5 to 6 V
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
power Dissipation (pd)
• 20 to 31 W
current Limit
• 125% of full load typical
Output Voltage temperature coefficient
• 100 ppm/°C max
Isolation at 25°c
• 100 megohm minimum at 500 V
audio rejection
• 50 dB typical
meChaniCal and envirOnmental
size (maximum)
• 2.705 x 2.205 x 0.400 inches (68.71 x 56.01 x 10.16 mm)
‣
See case S for dimensions.
Weight (maximum)
• 100 grams maximum
screening
Space Prototype, Class H, or Class K are radiation tolerant
to Radiation Hardness Assurance (RHA) levels of “-” (O), “P”,
“R”, or “F” per MIL-PRF-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 Screening Tables 1, 2 and 3 for more information. Available
configurations: OO, HP, HR, KP, KR, KF
www.craneae.com/interpoint
Page 3 of 22
SMRT28 Rev F - 2011.01.24
Crane Aerospace & Electronics Power Solutions
sMrt28 single, Dual and triple space Dc/Dc converters
28 VOLt Input – 35 Watt – space quaLIFIeD
t
rIm DOwn
Singles
Duals
trIM taBLes
t
rIm
u
p
Singles
Duals
R
trIm
should be connected between the
trim
pin and
positive sense
pin. R
trIm
should be connected between the
trim
pin and
sense return
pin.
R
trIm
should be connected between the
trim B
pin and
positive Vout B
pin. This only trims output B, output A can use the sense pin to trim up
only. See page 2 for instructions on trimming up output A.
R
trIm
should be connected between the
trim B
pin and
Vout B return
pin.
This only trims output B, output A can use the sense pin to trim up only.
Triples
Triples
R
trIm
should be connected between the
trim a
pin and
positive Vout
a
pin to adjust the Main output.
R
trIm
should be connected between the
trim B
pin and
positive Vout
B
pin to adjust the Auxiliary outputs.
R
trIm
= K (
Vout - Vmin
)
Vnom - Vout
R
trIm
should be connected between the
trim a
pin and
Vout a return
pin
to adjust the Main outputs.
R
trIm
should be connected between the
trim B
pin and
Vout B return
pin
to adjust the Auxiliary outputs.
R
trIm
= K (
Vmax - Vout
)
Vout - Vnom
Vout = Desired Voltage; K/Vmin/Vnom from table below.
Vout = Desired Voltage; K/Vmax/Vnom from table below.
V
nOM
3.3
5.0
7.0
8.7
12
15
K
3500
4520
8020
9040
11030
12900
V
MIn
3.18
4.16
5.47
6.13
7.05
7.65
% OF V
nOM
96
83
78
70
58
51
V
nOM
3.3
5.0
7.0
8.7
12
15
K
3000
3000
5300
5300
5300
5300
V
MAX
3.70
6.26
8.27
10.46
14.69
18.54
% OF V
nOM
112
125
118
149
122
124
note: Do not exceed maximum current rating when trimming down,
note: Do not exceed maximum power rating when trimming up.
1
2
3
4
5
SMRT Single
14
Trim 12
10
Sense 8
9
11
13
1
2
3
4
5
SMRT Single
14
Trim 12
10
8
11
13
Sense Return 9
1
2
3
4
5
Vout B Return 14
Trim B 12
10
9
8
11
13
1
2
3
4
5
SMRT Dual
Vout B 13
Trim B 12
10
9
8
1
2
3
4
5
SMRT Triple
11
14
SMRT Dual
1
2
3
4
5
SMRT Triple
Vout A 13
+Vout B 11
9
Trim A 12
10
14
Vout A Return 14
Trim A 12
Vout B Return 10
Trim B 8
9
11
13
Trim B 8
F
Igure
1: t
rIm
D
Own
D
IagramS
www.craneae.com/interpoint
F
Igure
2: t
rIm
u
p
D
IagramS
Page 4 of 22
SMRT28 Rev F - 2011.01.24
Crane Aerospace & Electronics Power Solutions
sMrt28 single, Dual and triple space Dc/Dc converters
28 VOLt Input – 35 Watt – space quaLIFIeD
Prim. Bias
Bias 1
28V
Vin
EMI Filter
Prim. Bias
PWM
Prim. Bias
Bias 1
Error Amp / ref /
compensation
OCP
Vout A
Sense
Trim
Sense Rtn.
Vout A Rtn.
Vin Rtn.
28V
Feed forward
compensation
Prim. Bias
Bias 1
Feedback
Isolation
Oscillator
Sync In
Sync Rtn.
Prim. Bias
Phase A
Clock
Phase B
28V
Bias 2
Prim. Bias
Inhibit
5.1V Z
PWM
OCP
Vout A
Vout A Rtn.
Bias 2
Isolation
Feedback
Oscillator
Primary
Secondary
F
Igure
3: Smrt S
Ingle
b
lOCk
D
Iagram
www.craneae.com/interpoint
Page 5 of 22
SMRT28 Rev F - 2011.01.24
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