description

The LCM-120™ line conditioning module is a non-isolated dc-dc

converter used to extend the input voltage range of Interpoint’s

dc-dc converters. The LCM-120 delivers up to 120 watts of

throughput power from a 12 to 50 volt dc source in one of three

modes:

• 12 to 24 volts input – internal boost converter

delivers 24 V

• 24 to 36 volts input – input is connected

directly to output

• 36 to 50 volts input – internal buck converter

delivers 36 V

The LCM-120 module is protected by internal current limit

circuitry which limits current according to input voltage. This

feature also allows safe charging of large external capacitors.

Because current is sensed between input common and output

common there is normally no external connection made between

these pins. (Note: If an external connection between input

and output common is desired, the resistance of this external

connection must be greater than 1 ohm.) The LCM module will

work through up to an 80 volt transient for up to 120 milliseconds

while holding the output at 36 VDC.

Features include an under voltage lockout, an inhibit input, a

synchronization input and a power fail flag output. Under voltage

lockout prevents start-up for inputs less than 12 volts dc and will

shut down the converter for an input of less than 10 volts dc. The

inhibit input, when connected to input common, disables the

internal converter and opens the output power path while leaving

the power fail flag unaffected. Inhibit is normally left open or

pulled up with a resistor. The sync input allows synchronization of

the LCM-120 module’s internal clock to an external pulse source

with LSTTL level voltages and a 40% to 60% duty cycle. When

unused, the sync should be left unconnected. The power fail flag

output is a fully isolated NPN opto-coupler transistor rated to 18

volts dc. It will drive an external LSTTL load low if the LCM-120

module’s input voltage drops below 10 volts dc and will remain

active until the module output voltage also drops below 10 volts

dc.

When the LCM-120 module is operated at 12 volts in and 120

watts output, line loss can become a major concern. The module

will output 24 volts at 120 watts. Allowing for efficiency, the input

current will be 120 watts / 0.88 / 12 = 11.36 A. If the resistance in

the line from the power source to the LCM-120 is 0.05 ohms, the

line loss at 12 volts from the power source will be (0.05 • 11.36)

= 0.57 volts. The LCM-120 module will see 11.43 volts and will

not start up.

Interpoint recommends a minimum output capacitance of 330 uF

and a total ESR of at least 0.25 ohms to ensure stability of the

LCM-120 module’s boost converter. For very low ESR capacitors,

an external series resistor (non-inductive) may be used to

obtain the minimum total ESR. The maximum recommended

capacitance is 1 F.

MODELS

VDC Output

LCM-120 24 to 36 VDC

Crane Aerospace & Electronics Power Solutions

LCM-120 Line Conditioning Module

Crane Aerospace & Electronics

Power Solutions – Interpoint Products

10301 Willows Rd. NE, Redmond, WA 98052

+1.425.882.3100 • power@crane-eg.com

www.craneae.com/interpoint

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LCM-120 Rev AA - 2013.06.14

28 Volt input – 120 watt

Features

powers dc-dc converters requiring 28 Vin

input voltage 12 to 50 Vdc

• Operating temperature -55° to +125°C

• Works through transients of

up to 80 V for up to 120 ms

• Inhibit function

• Synchronization function

• Undervoltage lockout