F
EATURES
•
•
•
•
•
•
•
•
•
•
–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
Up to 76% efficiency, 16 W/in
3
Size (max.):
Weight:
Screening:
DC/DC C
ONVERTERS
28 V
OLT
I
NPUT
MSA SERIES
5 WATT
MODELS
VDC O
UTPUT
SINGLE
5
5.2
12
15
60
DUAL
±5
±12
±15
1.075 x 1.075 x 0.270 inches (27.31 x 27.31 x 6.86 mm)
15 grams maximum.
Standard, ES, or 883 (Class H).
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.
W
IDE
V
OLTAGE
R
ANGE
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.
I
MPROVED
D
YNAMIC
R
ESPONSE
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%.
I
NHIBIT
F
UNCTION
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.
C
ONVERTER
D
ESIGN
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.
U
NDERVOLTAGE
L
OCKOUT AND
T
RANSIENT
P
ROTECTION
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.
1
INTERPOINT [ INTERPOINT CORPORATION COMPANY ]
