Crane Aerospace & Electronics Power Solutions
sMrt single, dual and triple space dc-dc converters
Features
19-56 Volt input – 35 Watt – space qualiFied
• Radiation tolerant space DC-DC converter
- Total ionizing dose (TID) guaranteed per MIL-STD-883
method 1019, radiation hardness assurance (RHA)
P = 30 krad(Si), L = 50 krad(Si), R = 100 krad(Si)
- 50 - 300 rad(Si)/sec dose rate (Condition A)
- 10 mrad(Si)/sec dose rate (Condition D)
- Single event effects (SEE) LET performance to
86 MeV cm
2
/mg
• Built in MIL-STD-461 EMI filter
• Output trim from 51% to 125% of nominal
• Operating temperature -55° to +125°C
• Input voltage range 19 to 56 volts
• Fully isolated, 5 port isolation
• Magnetic feedback
• Qualified to MIL-PRF-38534 Class H and K
• Transient protection 80 volts for 120 ms
• Remote sense
• Fixed high frequency switching
• Inhibit function
• Synchronization input
• Meets MIL-STD-704A transient standards
• Indefinite short circuit protection
MODELS
O
utput
V
Oltage
(V)
SINGLE
3.3
5
8.7
12
15
DUAL
Vout A 5 V, Vout B 5 V
Vout A 12 V, Vout B 12 V
Vout A 15 V, Vout B 15 V
TRIPLE
+3.3 & ±12
+3.3 & ±15
+5 & ±7
+5 & ±12
+5 & ±15
description
The Interpoint
®
SMRT Series™ of DC-DC converters offers
up to 35 watts of power in a radiation tolerant design. The low
profile SMRT converters are manufactured in our fully certified
and qualified MIL-PRF-38534 Class K 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 hardness assurance.
The SMRT converters are switching regulators which use
a two-phase, phase shifted flyback design with a nominal
switching frequency of 300 kHz. Tight regulation is maintained
with advanced constant frequency pulse width modulation
design techniques. The SMRT’s feed-forward compensation and
discontinuous topologies provide high levels of input-to-output
ripple rejection. See Figure 10 on page 29, Figure 29 and
Figure 30 on page 33 and Figure 45 and Figure 46 on page
36.
Crane Aerospace & Electronics
Power Solutions – Interpoint Products
10301 Willows Rd. NE, Redmond, WA 98052
+1 425.882.3100 • power@crane-eg.com
www.craneae.com/interpoint
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 dual-phase output
• Dual Output: Two isolated single-phase outputs
• Triple Output: One single-phased output (Main) isolated
from one single-phase dual output (± Auxiliary)
SMRT28 Rev AK - 2017.11.20
Page 1 of 44
Crane Aerospace & Electronics Power Solutions
sMrt single, dual and triple space dc-dc converters
19-56 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.
SMRT converters offer screening options to space prototype (O),
Class H or K and radiation hardness assurance (RHA) levels
P - 30 krad(Si), L - 50 krad(Si) or R - 100 krad(Si). Single event
effects (SEE) LET performance to 86 MeV cm
2
/mg. See Table 27
and Table 28 for more information.
S
creenIng
I
nhIbIt
F
unctIOn
The SMRT Series incorporates an inhibit terminal that can be
used to disable internal switching. It is not recommended to tie
the Inhibit pin of an SMRT directly to the Inhibit pin of another
converter as the SMRT Inhibit pin can sink current. When pulling
multiple inhibit signals low, a separate interface is recommended
for each SMRT. 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 an open circuit is applied to the Inhibit pin or the
Inhibit pin is open (unconnected). The open circuit voltage of the
Inhibit pin is 5 to 6 volts. To enable the converter use an open
collector on the Inhibit pin or leave it unconnected.
eMI
The SMRT 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.
e
lectrOStatIc
d
IScharge
(eSd) S
enSItIVIty
Per MIL-PRF-38534, the SMRT Series converters are rated to
ESD class 3B defined as sensitivity equal to, or greater than,
8000 volts.
Tight load regulation is maintained via wide bandwidth magnetic
feedback and through the use of remote sense on single output
models and V
OUT
A on dual output models. The sense pin
function allows a remote connection for the voltage regulation
circuit to compensate for voltage drops between the converter
and the point of use.
Note that if the sense pins are connected but the output voltage
pins are not, the converter may be damaged.
The maximum voltage drop from the output to the sense pin is
shown in Table 1 below.
S
enSe
S
ynchrOnIzatIOn
The Sync Input pin is isolated which allows Sync Return pin 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.
r
adIatIOn
t
Olerance
The SMRT 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 RHA level R converters will operate normally in radiation
environments with up to 100 krad(Si) total dose and will not
exhibit low dose rate (LDR) effects at 10 mrad(Si)/sec dose rate
up to a TID of 100 krad.
These levels of radiation tolerance make the SMRT converters
suitable for electronics in programs where operation in high
radiation environments is required.
NOMINAL OUTPUT
VOLTAGE (V)
1
3.3
2
5
8.7
2
12
15
MAx VOLTAGE
DROP (V)
0.58
1.0
1.9
2.68
3.36
MAx VOLTAGE AT
CONVERTER
(V
MAx
)
1
3.88
6.0
10.58
14.68
18.36
T
able
1: M
axiMuM
V
olTage
D
rop
u
sing
r
eMoTe
s
ense
s
ingle anD
D
ual
M
oDels only
Notes for Table 1
1. Do not exceed maximum voltage.
2. The sense pin function for 3.3 and 8.7 is only available on single output
models.
www.craneae.com/interpoint
SMRT28 Rev AK - 2017.11.20
Page 2 of 44
Crane Aerospace & Electronics Power Solutions
sMrt single, dual and triple space dc-dc converters
19-56 Volt input – 35 Watt – space qualiFied
O
utput
V
Oltage
t
rIM
There are two possible methods for output voltage trim. Trim can
be achieved using the provided trim pin or in some cases the
sense pin. The preferred method is the use of the trim pin. Every
converter in the SMRT family provides a trim pin that allows at
least one output to be adjusted. See Table 3 and Table 4 for
maximum adjust range for each output voltage. The single output
models provide a trim pin and remote sense. The dual output
models allow remote sense on V
OUT
A and have a trim pin on the
V
OUT
B. The triples have a trim pin on the V
OUT
A (main)and a
single trim pin for both V
OUT
B auxiliaries.
For outputs without a trim pin, the output at the converter can be
adjusted up by adding resistance in series with the sense pin.
See Table 2 for a summary of trim features and see below for
details on the trim features. See Formula 1 for trimming down
when using a trim pin, Formula 2 for trimming up when using a
trim pin and Formula 3 when trimming up using Sense A pin on a
dual output model.
NOTE: Do not exceed maximum current rating when trimming
down.
NOTE: Do not exceed maximum power rating when trimming up.
Trim Pin (Formulas 1 and 2)
Sense Pin (Formula 3)
Voltage Adjust Feature
Trim and Sense Pin
—
Singles
Sense A
Trim B
Duals
Trim A, Trim B ±
—
Triples
t
able
2: t
rIM and
S
enSe
V
Oltage
a
djuSt
O
utput
V
Oltage
t
rIM
d
etaIlS
The output voltage trim pin function is implemented with a
resistor between the trim pin and either the output voltage pin or
the sense pin. Figure 1 and Figure 2 show the connections for
the trim resistor (R
TRIM
).
1
2
3
4
5
SMRT Single
14
Vout A 13
Vout A 11
9
Sense 8
Trim 12
10
1
2
3
4
5
Vout A Return 14
13
SMRT Single
Trim 12
11
Sense Return 9
8
Vout A Return 10
1
2
1
2
3
4
5
SMRT Dual
14
Vout B 13
Trim B 12
11
9
10
8
1
2
3
4
5
SMRT Triple
Vout A Return 14
13
Trim A 12
11
9
Vout B Return 10
Trim B 8
3
4
5
SMRT Dual
Vout B Return 14
13
11
9
8
Trim B 12
10
1
2
3
4
5
SMRT Triple
14
Vout A 13
+Vout B 11
10
9
Trim B 8
Trim A 12
F
Igure
1: t
rIM
d
Own
d
IagraMS
F
Igure
2: t
rIM
u
p
d
IagraMS
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SMRT28 Rev AK - 2017.11.20
Page 3 of 44
Crane Aerospace & Electronics Power Solutions
sMrt single, dual and triple space dc-dc converters
19-56 Volt input – 35 Watt – space qualiFied
O
utput
V
Oltage
t
rIM
d
etaIlS
(
cOntInued
)
TRIM DOWN USING TRIM PIN, ALL MODELS
To trim the output voltage lower than the nominal set point,
connect R
TRIM
as shown in Figure 1. The value of R
TRIM
is
calculated by the following equation:
V
NOM
3.3
5 single and triple
5 dual
7
8.7
12
15
F
OrMula
1: t
rIM
d
Own
u
SIng
t
rIM
p
In
K
3500
4520
7040
8020
9040
11030
12900
V
MIN
3.18
4.16
4.38
5.47
6.13
7.05
7.65
% OF V
NOM
96
83
88
78
70
58
51
R
TRIM
= K V
OUT
– V
MIN
V
NOM
– V
OUT
Where:
K = Multiplication constant from Table 3
V
OUT
= Desired output voltage (must be greater than V
MIN
)
V
MIN
= Minimum output voltage from Table 3
V
NOM
= Nominal set point voltage of the converter
(
) / (
)
t
able
3: t
rIM
d
Own
c
OnStantS when
u
SIng
t
rIM
p
In
TRIM UP USING TRIM PIN, ALL MODELS
CAUTION:
-Do not exceed maximum current rating when trimming down.
-Do not make any connections between TRIM B, pin 8, and
VOUT B Negative, pin 9. Any connection between the two can
cause the auxiliary voltages to go excessively high and can
damage the converter.
To trim the output voltage higher than the nominal set point,
connect R
TRIM
as shown in Figure 2. The value of R
TRIM
is
calculated by the following equation:
V
NOM
3.3
5 single and triple
5 dual
7
8.7
12
15
F
OrMula
2: t
rIM
u
p
u
SIng
t
rIM
p
In
R
TRIM
= K V
MAx
– V
OUT
K
3000
3000
5280
5300
5300
5300
5300
V
MAx
3.70
6.26
5.82
8.27
10.46
14.69
18.54
% of V
NOM
112
125
116
118
120
122
124
(
Where:
K = Multiplication constant from Table 4
V
OUT
= Desired output voltage (must be less than V
MAx
)
V
MAx
= Maximum output voltage from Table 4
V
NOM
= Nominal set point voltage of the converter
) / (
V
OUT
– V
NOM
)
t
able
4: t
rIM
u
p
c
OnStantS when
u
SIng
t
rIM
p
In
TRIM UP USING SENSE A PIN ON DUAL MODELS ONLy
CAUTION:
-Do not exceed maximum power rating when trimming up.
-Do not make any connections between TRIM B, pin 8, and
VOUT B Negative, pin 9. Any connection between the two can
cause the auxiliary voltages to go excessively high and can
damage the converter.
F
OrMula
3: t
rIM
u
p
u
SIng
S
enSe
a p
In
R
ADjUST
= 240 V
out
–
V
nom
Where:
V
OUT
= Desired output voltage (must be less than V
MAx
)
V
NOM
= Nominal set point voltage of the converter
V
MAx
= Maximum achievable output voltage
Trim Up V
OUT
A
In addition to remote sensing, the Sense A pin may be used to
increase the regulated output voltage at the V
OUT
A pin. This
is accomplished by attaching a resistor (R
ADjUST
) between the
Sense A pin (pin 8) and the V
OUT
A pin (pin 11). The value of
R
ADjUST
is calculated by the following equation:
V
NOM
5
12
15
(
) / (
K +
(
V
max
–
V
out
))
K
1
0.98
1.134
V
MAx
6.00
12.98
16.13
% of V
NOM
120
108
107.5
CAUTION:
Do not exceed maximum power rating when trimming up.
t
able
5: t
rIM
u
p
c
OnStantS when
u
SIng
S
enSe
p
In On
O
utput
a
OF
d
ual
O
utput
M
OdelS
www.craneae.com/interpoint
SMRT28 Rev AK - 2017.11.20
Page 4 of 44
Crane Aerospace & Electronics Power Solutions
sMrt single, dual and triple space dc-dc converters
19-56 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
Vout A
Sense
Trim
Sense Rtn.
OCP
Vout A Rtn.
Vin Rtn.
28V
Feed forward
compensation
Prim. Bias
Feedback
Isolation
Sync In
Sync Rtn.
Prim. Bias
Phase A
Clock
Phase B
28V
Vout A Rtn.
Bias 2
Prim. Bias
Inhibit
5.1V Z
PWM
OCP
Vout A
Vout A Rtn.
Isolation
Feedback
Vout A Rtn.
Primary
Secondary
F
Igure
3: SMrt S
Ingle
b
lOck
d
IagraM
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SMRT28 Rev AK - 2017.11.20
Page 5 of 44
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