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

converterastheSMRT28Inhibitpincansinkcurrent.When

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

normaloperationwhenahigh(≥2.4V)signaloropencircuitis

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.

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.

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:

•Tripleoutputmodels:Mainoutputisoneset,thedualoutputs

are another set.

•Dualoutputs:Eachoutputisa“set.”

One set can be trimmed using the trim pin, the other set can

be trimmed (up only) using the positive sense pin.

•Single:Oneset

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-

total dose.

These levels of radiation tolerance make the SMRT28 converters

suitable for electronics in programs where operation in high radia-

tion environments is required.

an upset resulting in a dip in the voltage. This is non-destructive

to the unit. The converter will operate through the upset.

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.

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.

(see trim tables on page 4 for more options)

Vmax - Vout

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

between Sense A (pin 8) and Vout A (pin 11).

Crane Aerospace & Electronics Power Solutions

www.interpoint.com

Page 2 of 19

sMrt28 single, Dual and triple space Dc/Dc converters

28 VOLt Input – 35 Watt – space quaLIFIeD

SMRT28 Rev E - 20100216