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LC020A

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
10 Lineage Power
Data Sheet
April 2008
18 Vdc to 36 Vdc Inputs; 20 W
LC020 Single-Output Series Power Module:
Feature Descriptions (continued)
Remote On/Off
Two remote on/off options are available. Positive logic remote on/off turns the module on during a logic high volt-
age on the REMOTE ON/OFF pin, and off during a logic low. Negative logic device code suffix of “1,” remote on/off
turns the module off during a logic high and on during a logic low.
To turn the power module on and off, the user must supply a switch to control the voltage between the on/off termi-
nal and the V
I(–) terminal (Von/off). The switch can be an open collector or equivalent (see Figure 19). A logic low is
V
on/off = –0.7V to 1.2 V. The maximum Ion/off during a logic low is 1 mA. The switch should maintain a logic low volt-
age while sinking 1 mA.
During a logic high, the maximum V
on/off generated by the power module is 6 V. The maximum allowable leakage
current of the switch at V
on/off = 6 V is 50 µA.
The module has internal capacitance to reduce noise at the ON/OFF pin. Additional capacitance is not generally
needed and may degrade the start-up characteristics of the module.
8-758
Figure 19. Remote On/Off Implementation
Output Voltage Adjustment
Output voltage trim allows the user to increase or decrease the output voltage set point of a module. This is accom-
plished by connecting an external resistor between the TRIM pin and either the V
O(+) or VO(–) pins. With an exter-
nal resistor between the TRIM and V
O(+) pins (Radj-down), the output voltage set point (VO, adj) decreases. With an
external resistor between the TRIM pin and V
O(–) pin (Radj-up), VO,adj increases.
The following equations determine the required external resistor value to obtain an output voltage change of Δ%:
Device a b c d –5% V
O Radj-down +5% VO Radj-up
LC020F 14.0 51.10 5.19 2.70 110.9 kΩ 52.8 kΩ
LC020A 4.02 16.90 2.01 2.0 19.3 kΩ 23.3 kΩ
LC020B 15.40 15.40 1.58 9.80 246.5 kΩ 16.0 kΩ
LC020C 21.50 16.90 1.76 12.24 356.3 kΩ 18.2 kΩ
+
Ion/off
-
Von/off
REMOTE
ON/OFF
V
I(+)
V
I(-)
Radj-down
cd 100 Δ%–()100–⋅[]
Δ%
--------------------------------------------------------------b– kΩ=
Radj-up
100a
d Δ⋅ %
-----------------b– kΩ=
Lineage Power 11
Data Sheet
April 2008
18 Vdc to 36 Vdc Inputs; 20 W
LC020 Single-Output Series Power Module:
Feature Descriptions (continued)
Output Voltage Adjustment (continued)
The adjusted output voltage cannot exceed 110% of
the nominal output voltage between the V
O(+) and
V
O(–) terminal.
The modules have a fixed current-limit set point. There-
fore, as the output voltage is adjusted down, the avail-
able output power is reduced. In addition, the minimum
output current is a function of the output voltage. As the
output voltage is adjusted down, the minimum required
output current can increase.
Output Overvoltage Protection
The output overvoltage clamp consists of control cir-
cuitry, independent of the primary regulation loop, that
monitors the voltage on the output terminals. The con-
trol loop of the protection circuit has a higher voltage
set point than the primary loop (see Feature Specifica-
tions table).
In a fault condition, the overvoltage clamp ensures that
the output voltage does not exceed V
O, clamp, max. This
provides a redundant voltage control that reduces the
risk of output overvoltage.
Synchronization (Optional)
The unit is capable of external synchronization from an
independent time base with a switching rate of
256 kHz. The amplitude of the synchronizing pulse
train is TTL compatible and the duty cycle ranges
between 40% and 60%. Synchronization is referenced
to V
IN(+).
Thermal Considerations
Introduction
The LC020 power module operates in a variety of ther-
mal environments; however, sufficient cooling should
be provided to help ensure reliable operation of the
unit. Heat-dissipating components inside the unit are
thermally coupled to the case. Heat is removed by con-
duction, convection, and radiation to the surrounding
environment. Proper cooling can be verified by mea-
suring the case temperature. Peak case temperature
(T
C) occurs at the position indicated in Figure 20.
8-1265
Note: Dimensions are in millimeters and (inches).
Figure 20. Case Temperature Measurement
Location
Note that the view in Figure 20 is of the metal surface
of the module—the pin locations shown are for
reference. The temperature at this location should not
exceed 100 °C. The output power of the module should
not exceed the rated power for the module as listed in
the Ordering Information table.
Heat Transfer Without Heat Sinks
Increasing airflow over the module enhances the heat
transfer via convection. Figure 21 shows the maximum
power that can be dissipated by the module without
exceeding the maximum case temperature versus local
ambient temperature (T
A) for natural convection
through 3.0 ms
–1
(600 ft./min.).
Note that the natural convection condition was mea-
sured at 0.05 ms
–1
(10 ft./min.) to 0.1 ms
–1
(20 ft./min.);
however, systems in which these power modules may
be used typically generate natural convection airflow
rates of 0.3 ms
–1
(60 ft./min.) due to other heat dissipat-
ing components in the system. Use of Figure 21 is
shown in the following example.
Example
What is the minimum airflow necessary for an LC020A
operating at high line, an output current of 2.0 A, and a
maximum ambient temperature of 83 °C?
1212 Lineage Power
Data Sheet
April 2008
18 Vdc to 36 Vdc Inputs; 20 W
LC020 Single-Output Series Power Module:
Thermal Considerations (continued)
Heat Transfer Without Heat Sinks (continued)
Solution:
Given: V
I = 36 V, IO = 2.0 A, TA = 83 °C
Determine P
D (Figure 23): PD = 2.9 W
Determine Airflow (Figure 21): v = 1.0 ms
–1
(200 ft./min.)
8-1264
Figure 21. Forced Convection Power Derating with
No Heat Sink; Either Orientation
1-0337
Figure 22.LC020F Power Dissipation vs. Output
Current, T
A = 25 °C
8-1371
Figure 23. LC020A Power Dissipation vs. Output
Current, T
A = 25 °C
1-0338
Figure 24.LC020B Power Dissipation vs. Output
Current, T
A = 25 °C
1-0336
Figure 25.LC020C Power Dissipation vs. Output
Current, T
A = 25 °C
30 50 90
0
1.0
5.0
AMBIENT TEMPERATURE, T
A (˚C)
POWER DISSIPATION, PD (W)
40
1.5
2.0
2.5
3.0
3.5
60
0.5
70 80
4.0
4.5
5.5
6.0
6.5
100
3.0 ms
-1
(600 ft./min.)
NATURAL
CONVECTION
2.0 ms
-1
(400 ft./min.)
1.0 ms
-1
(200 ft./min.)
0.5 ms
-1
(100 ft./min.)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
POWER DISSIPATION, PD (W)
OUTPUT CURRENT, IO (A)
0.4 0.9 1.4 1.9 2.4 2.9 3.4 3.9
VI = 36 V
V
I = 27 V
V
I = 18 V
0.0 0.5 1.0 2.0 2.5 3.0 3.5
0
5
6
7
8
9
OUTPUT CURRENT, I
O
(A)
POWER DISSIPATION, PD (W)
4
4.01.5
3
VI = 36 V
VI = 28 V
VI = 18 V
1
2
VIN = 18 V
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
POWER DISSIPATION, PD (W)
OUTPUT CURRENT, IO (A)
0.16 0.36 0.56 0.76 0.96 1.16 1.36 1.56
VI = 36 V
V
I = 27 V
V
I = 18 V
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
POWER DISSIPATION, PD (W)
OUTPUT CURRENT, IO (A)
0.13 0.33 0.53 0.73 0.93 1.13 1.3
3
VI = 36 V
V
I = 27 V
V
I = 18 V
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LC020A

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