QHW100G1 Lineage Power, QHW100G1 Datasheet - Page 14

• Manufacturer Part Number: QHW100G1
• Manufacturer: Lineage Power

dc-dc Converters: 36 to 75 Vdc Input, 2.5 Vdc Output; 25 W to 50 W
Thermal Considerations
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.-lbs.).
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 22. Case-to-ambient thermal resis-
tance vs. airflow is shown, for various heat sink config-
urations, heights, and orientations, as shown in Figures
28 and 29. Longitudinal orientation is defined as when
the long axis of the module is parallel to the airflow
direction, whereas in the transverse orientation, the
long axis is perpendicular to the airflow. These curves
were obtained by experimental testing of heat sinks,
which are offered in the product catalog.
Figure 28. Case-to-Ambient Thermal Resistance
14
14
θ
ca
10
9
8
7
6
5
4
3
2
1
0
0
=
Curves; Transverse Orientation
ΔT
-------------------- -
(100)
0.5
P
C max
,
D
VELOCITY, m/s (ft./min.)
(200)
1.0
=
(
----------------------- -
T
D
(300)
C
1.5
):
P
–
D
C, max
T
A
NO HEAT SINK
1/4 IN. HEAT SINK
1/2 IN. HEAT SINK
1 IN. HEAT SINK
(continued)
)
(400)
2.0
) divided by the
(500) (600)
2.5
C
) is
8-2323 (F)
3.0
Figure 29. Case-to-Ambient Thermal Resistance
Figure 30. Heat Sink Power Derating Curves;
20
15
10
11
10
5
0
9
8
7
6
5
4
3
2
1
0
0
0
Curves; Longitudinal Orientation
10
Natural Convection; Transverse
Orientation
LOCAL AMBIENT TEMPERATURE, T
(100)
0.5
20
VELOCITY, m/s (ft./min.)
30
(200)
1.0
40
(300)
1.5
50
60
1 IN. HEAT SINK
1/2 IN. HEAT SINK
1/4 IN. HEAT SINK
NO HEAT SINK
NO HEAT SINK
1/4 IN. HEAT SINK
1/2 IN. HEAT SINK
1 IN. HEAT SINK
(400)
2.0
70
Lineage Power
April 2008
(500)
80
2.5
A
(°C)
90 100
8-2324 (F)
8-2889 (F)
(600)
3.0