JAHW075A Lineage Power, JAHW075A Datasheet - Page 16

• Manufacturer Part Number: JAHW075A
• Manufacturer: Lineage Power

dc-dc Converters; 36 to 75 Vdc Input, 5 Vdc Output; 50 to 100 W
Thermal Considerations
Heat Transfer with Heat Sinks
Example
If an 85 °C case temperature is desired, what is the
minimum airflow necessary? Assume the JAHW075A
module is operating at V
current of 15 A, maximum ambient air temperature of
55 °C, and the heat sink is 1/2 inch.
Solution
Given: V
Determine P
Then solve the following equation:
Use Figure 33 to determine air velocity for the 1/2 inch
heat sink.
The minimum airflow necessary for the JAHW075A
module is 0.5 m/s (100 ft./min.).
16
θ
θ
θ
ca
ca
ca
I
T
T
Heat sink = 1/2 inch
P
O
=
=
=
A
C
I
D
= 55 V
= 15 A
= 55 °C
= 85 °C
= 8 W
3.8 °C/W
D
(
----------------------- -
(
----------------------- -
T
85 55
by using Figure 31:
C
P
–
8
–
D
T
A
)
)
I
= 55 V and an output
(continued)
(continued)
Custom Heat Sinks
A more detailed model can be used to determine the
required thermal resistance of a heat sink to provide
necessary cooling. The total module resistance can be
separated into a resistance from case-to-sink (θcs) and
sink-to-ambient (θsa) as shown in Figure 34.
Figure 34. Resistance from Case-to-Sink and
For a managed interface using thermal grease or foils,
a value of θcs = 0.1 °C/W to 0.3 °C/W is typical. The
solution for heat sink resistance is:
This equation assumes that all dissipated power must
be shed by the heat sink. Depending on the user-
defined application environment, a more accurate
model, including heat transfer from the sides and bot-
tom of the module, can be used. This equation pro-
vides a conservative estimate for such instances.
EMC Considerations
For assistance with designing for EMC compliance,
please refer to the FLTR100V10 data sheet
(FDS01-043EPS).
Layout Considerations
Copper paths must not be routed beneath the power
module standoffs. For additional layout guidelines,
refer to the FLTR100V10 data sheet (FDS01-043EPS).
θ
sa
=
P
D
Sink-to-Ambient
(
------------------------ -
T
C
P
T
–
C
D
T
A
)
–
θcs
θ
cs
T
S
θsa
Lineage Power
Data Sheet
April 2008
T
A
8-1304 (F).e