Data Sheet
April 2008
JAW050A and JAW075A Power Modules; dc-dc Converters:
36 Vdc to 75 Vdc Input, 5 Vdc Output; 50 W to 75 W
Thermal Considerations
(continued)
POWER DISSIPATION, P
D
(W)
12
11
10
9
8
7
6
5
4
3
0
1
2
3
4
5
6
7
8
9
10
8-3336(F)
Introduction
(continued)
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.
Although the maximum case temperature of the power
modules is 100 °C, you can limit this temperature to a
lower value for extremely high reliability.
V
I
= 75 V
V
I
= 55 V
V
I
= 36 V
Heat Transfer Without Heat Sinks
Increasing airflow over the module enhances the heat
transfer via convection. Figures 21 and 22 show the
maximum power that can be dissipated by the module
without exceeding the maximum case temperature ver-
sus local ambient temperature (T
A
) for natural convec-
tion through 4 m/s (800 ft./min.). Note that the thermal
performance is orientation dependent. Longitudinal ori-
entation occurs when the long direction of the module
is parallel to the airflow, whereas transverse orientation
occurs when the short direction of the module is paral-
lel to the airflow.
Note that the natural convection condition was mea-
sured at 0.05 m/s to 0.1 m/s (10 ft./min. to 20 ft./min.);
however, systems in which these power modules may
be used typically generate natural convection airflow
rates of 0.3 m/s (60 ft./min.) due to other heat-dissipat-
ing components in the system. The use of Figure 22 is
shown in the following example.
Example
What is the minimum airflow necessary for a JAW075A
operating at V
I
= 55 V, an output current of 15 A, trans-
verse orientation, and a maximum ambient tempera-
ture of 55 °C?
Solution
Given: V
I
= 55 V
I
O
= 15 A
T
A
= 55 °C
Determine P
D
(Use Figure 20.):
P
D
= 14 W
Determine airflow (v) (Use Figure 22.):
v = 2.3 m/s (460 ft./min.)
OUTPUT CURRENT, I
O
(A)
Figure 19. JAW050A Power Dissipation vs.
Output Current at 25 °C
16
15
14
13
12
11
10
9
8
7
6
5
4
1
POWER DISSIPATION, P
D
(W)
V
I
= 75 V
V
I
= 55 V
V
I
= 36 V
2
3
4
5
6
7
8
9 10 11 12 13 14 15
OUTPUT CURRENT, I
O
(A)
8-3337(F)
Figure 20. JAW075A Power Dissipation vs.
Output Current at 25 °C
Lineage Power
11
LINEAGEPOWER [ LINEAGE POWER CORPORATION ]
