MODELS

1

Size (max.):

1.075 x 1.075 x 0.270 inches (27.31 x 27.31 x 6.86 mm)

Weight:

15 grams maximum.

Screening:

Standard, ES, or 883 (Class H).

SINGLE

5

5.2

12

15

60

DUAL

±5

±12

±15

DESCRIPTION

The MSA Series™ of high frequency DC/DC converters offers a new

standard of performance for low power, military/aerospace grade

DC/DC converters. MSA parts provide up to 5 watts output power

over the full military temperature range with up to 76% efficiency.

Thick-film hybrid techniques provide military/aerospace reliability

levels and optimum miniaturization. The hermetically sealed case is

only 1.075 by 1.075 inches — with a height of only 0.270 inches.

Power density for the MSA Series parts is 16 watts per cubic inch.

The MSA Series’ small size, low height, and hermetically sealed

metal enclosures make them ideal for use in military, aerospace and

other high reliability applications. Units are available with standard,

screening, “ES”,

and fully compliant SMD “883” screening. See

page 8 for screening options and descriptions.

The MSA 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 path 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. Up to 4 watts, 80% of the total output power, is available

from either output, provided that the opposite output is simultane-

ously carrying 20% of the total power. Each output must carry a

minimum of 20% of the total output power in order to maintain spec-

ified regulation on the negative output. Predictable current limit is

accomplished by direct monitoring 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 MSA converters are designed to provide full power operation

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

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

with derated power. Please refer to the low line dropout graphs

(Figures 17 and 18) for details. A low voltage lockout feature keeps

the converter shutdown below approximately 13 VDC to ensure

smooth initialization.

The MSA 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%.

MSA 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 (

≤0.8 V) 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 V. In the inhibit mode, a

maximum of 4 mA must be sunk from the inhibit pin.

Undervoltage lockout helps keep system current levels low during

initialization or re-start operations. They can withstand short term

transients of up to 50 volts without damage.

MSA SERIES

5 WATT

• –55° to +125°C operation

• 16 to 40 VDC input

• Fully isolated

• Optocoupler feedback

• Fixed frequency, 550 kHz typical

(400 kHz typ. 60 V output model)

• Topology – Flyback

• 50 V for up to 50 ms transient protection

• Inhibit function

• Indefinite short circuit protection