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:

1. 12 to 24 volts input – internal boost converter delivers 24 volts

2. 24 to 36 volts input – input is connected directly to output

3. 36 to 50 volts input – internal buck converter delivers 36 volts.

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

converters 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

1F.

B6-9

LCM-120

120 WATT

• _55°C to +125°C

• 12 to 50 VDC input

• Works through transients of

up to 80 V for up to 20 ms.

• Powers DC/DC converters

requiring 28 Vin nominal

• Undervoltage lockout

• Inhibit function

• Sync function

MODEL

LCM-120

Output 24

to 36 VDC

Size (max.): 1.505 x 3.005 x 0.400 inches

(38.23 x 76.33 x 10.16 mm)

See Section B8, case U1, for dimensions.

Weight:

95 grams max.

Screening:

Standard or ES. See Section C2 for screening

options, see Section A5 for ordering information.