Lineage Power 11
Data Sheet
April 2008
36 Vdc to 75 Vdc Inputs; 20 W
LW020 Single-Output-Series Power Modules:
Feature Descriptions (continued)
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
I(+).
Thermal Considerations
Introduction
The LW020 Single-Output-Series power module oper-
ates in a variety of thermal environments; however, suf-
ficient cooling should be provided to help ensure
reliable operation of the unit. Heat-dissipating compo-
nents inside the unit are thermally coupled to the case.
Heat is removed by conduction, convection, and radia-
tion to the surrounding environment. Proper cooling
can be verified by measuring the case temperature.
Peak case temperature (T
C) occurs at the position indi-
cated in Figure 15.
8-1265(C)
Note: Dimensions are in millimeters and (inches). Pin locations are
for reference only.
Figure 15. Case Temperature Measurement
Location
Note that the view in Figure 15 is of the metal surface
of the module—the pin locations shown are for refer-
ence. The temperature at this location should not
exceed the maximum case temperature indicated in
the derating curve shown in Figure 16. The output
power of the module should not exceed the rated
power for the module as listed in the Ordering Informa-
tion table.
Heat Transfer
Increasing airflow over the module enhances the heat
transfer via convection. Figure 16 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.).
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-dissipating com-
ponents in the system. Therefore, the natural convec-
tion condition represents airflow rates of up to 0.3 ms
–1
(60 ft./min.). Use of Figure 16 is shown in the following
example.
Example
What is the minimum airflow necessary for a LW020A
operating at V
I = 48 V, an output current of 3.6 A, and a
maximum ambient temperature of 85 °C?
Solution:
Given: V
I = 48 V, IO = 3.6 A, TA = 85 °C
Determine P
D (Figure 18): PD = 4.5 W
Determine airflow (Figure 16): v = 1.0 ms
–1
(200 ft./min.)
8-1264(C).a
Note: Conversion factor for linear feet per minute to meters per
second: 200 ft./min. = 1 ms
–1
.
Figure 16. Forced Convection Power Derating;
Either Orientation
40 60 100
0
2
MAX AMBIENT TEMPERATURE, T
A (˚C)
POWER DISSIPATION, PD (W)
50 70 80 90
1
3
4
5
110
120
6
7
3.0 ms
-1
(600 ft./min.)
2.0 ms
-1
(400 ft./min.)
MAX CASE
TEMPERATURE
NATURAL
CONVECTION
1.0 ms
-1
(200 ft./min.)
