JW050M Lineage Power, JW050M Datasheet - Page 10

• Manufacturer Part Number: JW050M
• Manufacturer: Lineage Power

dc-dc Converters; 36 to 75 Vdc Input, 1.5 Vdc Output; 15 W to 45 W
Thermal Considerations
Heat Transfer Without Heat Sinks
Increasing airflow over the module enhances the heat
transfer via convection. Figure 15 shows the maximum
power that can be dissipated by the module without
exceeding the maximum case temperature versus local
ambient temperature (T
through 4 m/s (800 ft./min.).
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 15 is
shown in the following example.
Example
What is the minimum airflow necessary for a JW100M
operating at V
maximum ambient temperature of 40 °C?
Solution
Given: V
Determine P
Determine airflow (v) (Use Figure 15.):
Figure 15. Forced Convection Power Derating with
10
10
35
30
25
20
15
10
I
T
P
v = 1.5 m/s (300 ft./min.)
5
0
O
A
0
I
D
= 54 V
= 20 A
= 40 °C
= 14.3 W
No Heat Sink; Either Orientation
0.1 m/s (NAT. CONV.)
D
10
I
(Use Figure 16.):
= 54 V, an output current of 20 A, and a
LOCAL AMBIENT TEMPERATURE, T
20
(20 ft./min.)
30
A
) for natural convection
40
50
60
(continued)
4.0 m/s (800 ft./min.)
3.5 m/s (700 ft./min.)
3.0 m/s (600 ft./min.)
2.5 m/s (500 ft./min.)
2.0 m/s (400 ft./min.)
1.5 m/s (300 ft./min.)
1.0 m/s (200 ft./min.)
0.5 m/s (100 ft./min.)
70
A
80
(°C)
90
8-1150 (C).a
100
Figure 16. JW100M Power Dissipation vs.
Heat Transfer with Heat Sinks
The power modules have through-threaded, M3 x 0.5
mounting holes, which enable heat sinks or cold plates
to attach to the module. The mounting torque must not
exceed 0.56 N-m (5 in.-lb.). For a screw attachment
from the pin side, the recommended hole size on the
customer’s PWB around the mounting holes is
0.130 ± 0.005 inches. If a larger hole is used, the
mounting torque from the pin side must not exceed
0.25 N-m (2.2 in.-lb.).
Thermal derating with heat sinks is expressed by using
the overall thermal resistance of the module. Total
module thermal resistance (θca) is defined as the max-
imum case temperature rise (ΔT
module power dissipation (P
The location to measure case temperature (T
shown in Figure 14. Case-to-ambient thermal resis-
tance vs. airflow is shown, for various heat sink config-
urations and heights, in Figure 17. These curves were
obtained by experimental testing of heat sinks, which
are offered in the product catalog.
θ
ca
16
14
12
10
8
6
4
2
0
=
0
Output Current at 25 °C
ΔT
-------------------- -
2
P
C max
,
D
4
OUTPUT CURRENT, I
6
=
8
(
----------------------- -
T
D
C
):
P
10
–
D
V
V
V
C, max
T
I
I
I
= 36 V
= 54 V
= 72 V
A
12
)
O
) divided by the
14
(A)
Lineage Power
April 2008
16
C
) is
18
8-2118 (C)
20