45

®

SMSA SERIES

5 WATT

MODELS

SINGLE

3.3

5

12

15

DUAL

±5

±12

±15

Size (max.): 1.075 x 1.075 x 0.270 inches

(27.31 x 27.31 x 6.86 mm)

See Figures 23 and 24 for dimensions.

Weight:

15 grams maximum.

Screening:

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

Radiation hardness levels O or R

Available configurations: OO, HO, HR, KR

DESCRIPTION

The SMSA Series™ of high frequency DC/DC converters offers a

new standard of performance for low power, space qualified DC/DC

converters. SMSA converters provide up to 5 watts output power

over the full military temperature range of –55°C to +125°C with up

to 76% efficiency. Thick-film hybrid techniques provide military/aero-

space reliability levels and optimum miniaturization. The hermeti-

cally sealed case is only 1.075 by 1.075 inches — with a height of

only 0.270 inches. Power density for the SMSA Series converters is

16 watts per cubic inch. The SMSA Series’ small size, light weight,

and hermetically sealed metal packages make them ideal for use in

space, military, aerospace and other high reliability applications.

SMSA converters offer three screening options – Space prototype

Class H, or Class K – and two levels of radiation hardness. See

Tables 1 through 3 for more information. Detailed reports on product

performance are also available and are listed in Table 4.

The SMSA converters are switching regulators that use a flyback

converter design with a constant switching frequency of 550 kHz.

They are regulated, isolated units using a pulse width modulated

topology and built as high reliability thick-film hybrids. Isolation

between input and output circuits is provided with a transformer in

the forward power loop and an optical link in the feedback control

loop. Excellent input line transient response and audio rejection is

achieved by an advanced feed-forward compensation technique.

Negative output regulation is maintained by tightly coupled

magnetics. Predictable current limit is accomplished by direct moni-

toring of the output load current, which results in a constant current

output above the overload point. Internal input and output filters

eliminate the need for external capacitors.

The SMSA converters are designed to provide full power operation

over the full 16 to 40 VDC voltage range. An undervoltage lockout

feature keeps the converter shutdown below approximately 13 VDC

to ensure smooth initialization.

The SMSA feed-forward compensation system provides excellent

dynamic response and noise rejection. Audio rejection is typically 50

dB. The minimum to maximum step line transient response is typi-

cally less than 1%.

SMSA converters provide a TTL open collector-compatible inhibit

feature that can be used to disable internal switching and inhibit the

unit’s output. Inhibiting in this manner results in low standby current,

and no generation of switching noise.

The converter is inhibited when the 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 4 mA must be sunk from the inhibit pin at 28 VDC input.

• Fully qualified to Class H or K

• Radiation hardened

• –55° to +125°C operation

• 16 to 40 VDC input

• Fully isolated

• Optocoupler feedback

• Fixed frequency, 550 kHz typical

• Topology – Single Ended Flyback

• Inhibit function

• Indefinite short circuit protection

• 5 watts output power

• Up to 76% efficiency