1

MODELS

SINGLE

3.3

5

12

15

DUAL

±5

±12

±15

SMTR SERIES

30 WATT

DESCRIPTION

The SMTR Series™ of 28 volt DC/DC converters offers up to

30 watts of output power from single or dual output configurations.

The operate over the full military temperature range of –55°C to

+125°C with up to 84% efficiency. SMTR converters are packaged

in hermetically sealed metal enclosures, making them ideal for use

in military, aerospace and other high reliability applications.

SMTR converters offer three screening options (Standard, Class H,

or Class K) and two levels of radiation hardness (O or R). See

Tables 1, 2, and 3 for more information. Detailed reports on product

performance are also available and are listed in Table 4.

The SMTR converters are constant frequency, pulse-width mod-

ulated switching regulators which use a quasi-square wave, single

ended, forward converter design. Tight load regulation is maintained

by using a wide bandwidth magnetic feedback and, on single output

models, through use of remote sense. On dual output models, the

positive output is independently regulated and the negative output is

cross regulated through the use of tightly coupled magnetics.

Indefinite short circuit protection and overload protection are

provided by a constant current-limit feature. This protective system

senses current in the converter’s secondary stage and limits it to

approximately 115% of the maximum rated output current.

SMTR converters are provided with internal filtering capacitors that

help reduce the need for external components in normal operation.

For systems that require compliance with MIL-STD-461C’s CE03

standard, Interpoint offers filter/transient suppression modules

(including the FMC-461, FMD-461 and FM-704A series filters) which

will result in compliance. For the lowest noise performance, connec-

tion of the case to input common is recommended. The connection

can be hard-wired or AC coupled with a small ceramic bypass

capacitor.

Synchronizing the converter with the system clock allows the

designer to confine switching noise to clock transitions, minimizing

interference and reducing the need for filtering. In sync mode, the

converter will run at any frequency between 500 kHz and 675 kHz.

The sync control operates with a quasi-TTL signal at any duty cycle

between 40% and 60%. The sync pin should be connected to input

common pin when not in use.

SMTR converters are designed to provide full power operation over

a full 16 to 40 Vdc voltage range. Operation below 16 volts,

including MIL-STD-704D emergency power conditions is possible

with derated power.

The SMTR Series feed-forward compensation system provides

excellent dynamic response and noise rejection. Audio rejection is

typically 50 dB. The min. to max. step line transient response is typi-

cally less than 4%.

SMTR 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 TTL

compatible low (

≤0.8V) 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 9 to 11 Vdc. In the inhibit mode, a maximum of 8 mA must be sunk

from the inhibit pin.

Size (max.): Non-flanged Case: H2 2.125 x 1.125 x 0.400 inches (53.98 x 28.58 x 10.16 mm)

Flanged Case: K3 2.910 x 1.125 x 0.400 inches (73.79 x 28.58 x 10.16 mm)

See Figures 22 through 25 for dimensions.

Weight:

Non-flanged 52 grams max., flanged 55 grams max.

Screening: Space prototype, Class H, or Class K (MIL-PRF-38534)

Radiation hardness levels O or R

• Fully qualified to Class H or K

• Radiation hardened

• –55° to +125°C operation

• 16 to 40 VDC input

• Fully Isolated

• Magnetic feedback

• Fixed frequency, 600 kHz typical

• Topology – Single Ended Forward

• Inhibit function

• Sync function

• Indefinite short circuit protection

• Up to 30 watts output power

• Trim function on single

output models

• Up to 81% efficiency

®