LIM SERIES
50 - 250 WATT
L
INE
I
NTERFACE
M
ODULE
40 TO 80 VDC INPUT
FEATURES
• -55°C to +125°C operation
• 40 to 80 VDC input
• Fixed frequency, 550 kHz typical
• Topology – Non-isolated buck
MODEL
THROUGHPUT POWER
• 35 VDC input with lowered efficiency
• Withstands transients of
up to 90 V for up to120 ms.
• 35 VDC output
MODEL
LIM5050™
LIM50250™
WATTS
50
250
• Inhibit function
• Power readiness function
• Load fault/short circuit protection
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• Up to 94% efficiency, 90 W/in
LIM5050
Size (max.): Non flanged
1.460 x 1.130 x 0.330 (37.08 x 28.70 x 8.38 mm)
Flanged
2.005 x 1.130 x 0.330 (50.93 x 28.70 x 8.38 mm)
See Section B8, cases E1 and G1, for dimensions.
30 grams typical
Weight:
Screening: Standard, ES, or 883
See Section C2 for screening options, see Section
A5 for ordering information.
DESCRIPTION
The LIM50™ Series of line interface modules provide a nominal
output voltage of 35 VDC from input voltages of 45 to 75 VDC with
efficiencies of 94% or higher. Sustained operation at voltages as
high at 80 or as low as 35 are possible with reduced efficiency. The
LIM5050 module delivers 50 watts of output power over the full mili-
tary temperature range of –55°C to +125°C and fits in a package of
1.460 x 1.130 x 0.330 inches (37.08 x 28.70 x 8.38 mm) maximum,
When the overload condition forces the output voltage to drop the
maximum current delivered falls from approximately 1.9 amps to
less than 1.5 amps. This feature keeps the short circuit dissipation
low and forces the output voltage to collapse rapidly thereby
preventing operation in an abnormal condition. Combined with the
“Power Ready” signal (see below), this foldback of the output
current prevents power cycling of the downstream converters.
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resulting in a power density of 91 watts/in .
POWER READY SIGNAL
SCREENING
To avoid high current surges during power up, the interface module
has a signal intended to connect to the inhibit lines of Interpoint
converters to keep these converters turned off until the interface
module’s output exceeds approximately 13 volts thereby assuring
that, in an overload condition, the converters powered by the inter-
face module will shut off before the power ready signal turns them
off. This feature prevents repeated limit cycling in an overload condi-
tion.
The LIM Series™ modules offer three screening options – Standard,
ES, or 883. See Section C2, Screening, for descriptions.
CONVERTER DESIGN
The LIM5050 modules are non-isolated converters operating at a
frequency between 500 kHz and 600 kHz. The control circuitry uses
average current mode control to achieve a wide bandwidth with little
or no overshoot over a wide range of loads. These converters are
specifically designed to accommodate loads with a negative imped-
ance such as those presented by Interpoint DC/DC converters with
a constant power consumption.
INHIBIT
The LIM Series modules have an open collector TTL compatible
inhibit terminal that can be used to disable power conversion,
resulting in a very low quiescent input current and no generation of
switching noise.
PARALLEL OPERATION: UP TO 10 MODULES
Up to 10 LIM Series modules can be paralleled for increased power.
Current sharing is typically within 2%.
Future offerings are planned for the LIM Series of modules.
Please contact your Interpoint representative listed in Section
A5, for more details.
OVERLOAD AND CURRENT LIMIT
Current overload protection is accomplished by monitoring the
output current resulting in a constant current mode when the load
exceeds approximately 125% of rated load at full output voltage.
B6-13