Crane Aerospace & Electronics Power Solutions
sMrt28 singlꢂ, Dꢀꢄl ꢄnd tꢃiplꢂ spꢄꢇꢂ Dc/Dc convꢂꢃꢁꢂꢃꢈ
28 VOLt Iꢆꢅut – 35 Watt – sꢅace quaLIFIeD
At the highest dose rate (1011 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.
un D e r V O l t a g e lO C k O u t
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.
SC r e e n I n g
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.
In h I b I t Fu n C t I O n
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
converterꢀasꢀtheꢀSMRT28ꢀInhibitꢀpinꢀcanꢀsinkꢀcurrent.ꢀWhenꢀ
pulling multiple inhibit signals low a separate interface is recom-
mended 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
normalꢀoperationꢀwhenꢀaꢀhighꢀ(≥ꢀ2.4ꢀV)ꢀsignalꢀorꢀopenꢀcircuitꢀisꢀ
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.
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.
Se n S e
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.
Sy n C h r O n I z a t I O n
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.
Se n S e Ad j u S t In S t r u c t I o n S f o r
ou t p u t A o n du A l Mo d e l S
Ad j u S t up on l y
(sꢂꢂ ꢁꢃim ꢁꢄblꢂꢈ on pꢄgꢂ 4 foꢃ moꢃꢂ opꢁionꢈ)
Ou t p u t VO l t a g e tr I m
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:
•ꢀTripleꢀoutputꢀmodels:ꢀMainꢀoutputꢀisꢀoneꢀset,ꢀtheꢀdualꢀoutputsꢀ
are another set.
•ꢀDualꢀoutputs:ꢀEachꢀoutputꢀisꢀaꢀ“set.”
One set can be trimmed using the trim pin, the other set can
be trimmed (up only) using the positive sense pin.
•ꢀSingle:ꢀOneꢀset
Vout - Vnom
Vmax - Vout
RaD j u S t = 240
(
)
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
ra D I a t I O n tO l e r a n C e
The SMRT28 DC/DC converters are designed to provide contin-
uous normal operation through radiation levels associated with
space missions and in tactical and strategic military environ-
ments. The converters will operate normally in radiation environ-
ments with up to 1 x 1012 neutrons per square centimeter neutron
fluence, 1011 rad(Si) per second dose rate, and 3x105 rad(Si)
total dose.
ꢀote: RADJUST should be connected
between Sense A (pin 8) and Vout A (pin 11).
These levels of radiation tolerance make the SMRT28 converters
suitable for electronics in programs where operation in high radia-
tion environments is required.
www.interpoint.com
Page 2 of 19
SMRT28 Rev E - 20100216
CRANE [ Crane Aerospace & Electronics. ]
