JAHW075A Lineage Power, JAHW075A Datasheet - Page 15

• Manufacturer Part Number: JAHW075A
• Manufacturer: Lineage Power

April 2008
Thermal Considerations
Heat Transfer without Heat Sinks
Figure 32.JAHW100A 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.).
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 27. Case-to-ambient thermal resis-
tance vs. airflow is shown, for various heat sink config-
urations and heights, in Figure 33. These curves were
obtained by experimental testing of heat sinks, which
are offered in the product catalog.
Lineage Power
14
12
10
8
6
4
2
0
θ
ca
1
V
V
V
2
I
I
I
=
= 36 V
= 48 V
= 75 V
Output Current at 25 °C
3
ΔT
-------------------- -
4
5
P
C max
,
D
6
7
OUTP UT CURRE NT, I
8
=
9
10 11 12 13 14 15 16 17 18 19 20
(
----------------------- -
T
D
C
):
P
–
D
dc-dc Converters; 36 to 75 Vdc Input, 5 Vdc Output; 50 to 100 W
C, max
T
O
A
(A )
(continued)
)
) divided by the
(continued)
C
) is
1-0465
Figure 33. JAHW050A and JAHW075A Case-to-
These measured resistances are from heat transfer
from the sides and bottom of the module as well as the
top side with the attached heat sink; therefore, the
case-to-ambient thermal resistances shown are gener-
ally lower than the resistance of the heat sink by itself.
The module used to collect the data in Figure 33 had a
thermal-conductive dry pad between the case and the
heat sink to minimize contact resistance. The use of
Figure 33 is shown in the following example.
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
Ambient Thermal Resistance Curves;
Either Orientation
0
(100)
0.5
AIR VELOCITY, m/s (ft./min.)
(200)
1.0
(300)
1.5
1 1/2 IN. HEAT SINK
1 IN. HEAT SINK
1/2 IN. HEAT SINK
1/4 IN. HEAT SINK
NO HEAT SINK
(400)
2.0
(500) (600)
2.5
3.0
8-2239 (F)
15