F
EATURES
鈥?_55擄C to +125擄C
鈥?12 to 50 VDC input
鈥?Works through transients of
up to 80 V for up to 20 ms.
鈥?Powers DC/DC converters
requiring 28 Vin nominal
鈥?Undervoltage lockout
鈥?Inhibit function
鈥?Sync function
L
INE
C
ONDITIONING
M
ODULE
28 V
OLT
I
NPUT
LCM-120
LCM-120
120 WATT
MODEL
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.
DESCRIPTION
The LCM-120鈩?Line Conditioning Module is a non-isolated DC/DC
converter used to extend the input voltage range of Interpoint鈥檚
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 鈥?internal boost converter delivers 24 volts
2. 24 to 36 volts input 鈥?input is connected directly to output
3. 36 to 50 volts input 鈥?internal buck converter delivers 36 volts.
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鈥檚 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鈥檚 input
voltage drops below 10 volts DC and will remain active until the
module output voltage also drops below 10 volts DC.
C
ONVERTER
D
ESIGN
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.
L
OW
V
IN AND
H
EAVY
L
OADS
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 鈥?11.36) = 0.57 volts.
The LCM-120 module will see 11.43 volts and will not start up.
F
EATURES
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
E
XTERNAL
C
APACITANCE
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鈥檚 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
1
2
3
4
5
6
7
