JBW050F Lineage Power, JBW050F Datasheet - Page 12

• Manufacturer Part Number: JBW050F
• Manufacturer: Lineage Power

JBW050F Power Modules: dc-dc Converter;
36 to 75 Vdc Input, 3.3 Vdc Output; 33 W
Figure 19. Forced Convection Power Derating with
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 (∆T
module power dissipation (P
The location to measure case temperature (T
shown in Figure 17. Case-to-ambient thermal resis-
tance vs. airflow is shown, for various heat sink config-
urations and heights, in Figure 20. These curves were
obtained by experimental testing of heat sinks, which
are offered in the product catalog.
12
12
12
10
8
6
4
2
0
0
θ
NATURAL CONVECTION
ca
3.0 m/s (600 ft./min.)
2.0 m/s (400 ft./min.)
1.0 m/s (200 ft./min.)
0.5 m/s (100 ft./min.)
0.25 m/s (50 ft./min.)
=
MAX CASE TEMP
No Heat Sink; Either Orientation
20
∆T
-------------------- -
LOCAL AMBIENT TEMPERATURE, T
P
C max
,
D
40
=
(
----------------------- -
T
60
D
C
):
P
–
D
C, max
T
A
)
80
) divided by the
A
(˚C)
100
C
) is
1-0705
120
Thermal Considerations
Heat Transfer with Heat Sinks
Figure 20. Case-to-Ambient Thermal Resistance
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 20 had a
thermal-conductive dry pad between the case and the
heat sink to minimize contact resistance. The use of
Figure 20 is shown in the following example.
Example
If an 85 °C case temperature is desired, what is the
minimum airflow necessary? Assume the JBW050F
module is operating at V
of 10 A, maximum ambient air temperature of 70 °C,
and the heat sink is 1/2 inch.
Solution
Given: V
Determine P
Then solve the following equation:
θca
θca
θca
=
=
=
8
7
6
5
4
3
2
1
0
0
1.95 °C/W
85 70
----------------- -
I
T
T
Heat sink = 1/2 in.
P
T
------------------- -
O
A
C
I
D
C
7.7
0.25
(50)
P
–
= 10 A
= 54 V
= 70 °C
= 85 °C
–
Curves; Either Orientation
= 7.7 W
D
D
T
A
by using Figure 18:
(100)
0.51
AIR VELOCITY, ms
(150)
0.76
Tyco Electronics Power Systems
I
(200)
NO HEAT SINK
1/4 in. HEAT SINK
1/2 in. HEAT SINK
1 in. HEAT SINK
1 1/2 in. HEAT SINK
1.02
= 54 V and an output current
September 20, 2004
(250)
1.27
-1
(ft./min.)
(continued)
(300)
1.52
(continued)
(350)
1.78
Data Sheet
(400)
2.03
8-1052.a