Data Sheet
October 1997
12
12
Tyco Electronics Corp.
18 Vdc to 36 Vdc Input, 12 Vdc Output; 50 W to 100 W
JC050B, JC075B, JC100B Power Modules: dc-dc Converters;
Thermal considerations (continued)
Heat Transfer Without Heat Sinks (continued)
8-1494
Figure 23. JC075B Power Dissipation vs.
Output Current
8-1250
Figure 24. JC100B Power Dissipation vs.
Output Current
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 (
∆TC, max) divided by the
module power dissipation (PD):
The location to measure case temperature (TC) is
shown in Figure 20. Case-to-ambient thermal resis-
tance vs. airflow is shown, for various heat sink config-
urations and heights, in Figur e25. These curves were
obtained by experimental testing of heat sinks, which
are offered in the product catalog.
8-1153
Figure 25. Case-to-Ambient Thermal Resistance
Curves; Either Orientation
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 Figur e25 had a
thermal-conductive dry pad between the case and the
heat sink to minimize contact resistance. The use of
Figure 25 is shown in the following example
0
0
2
4
8
16
20
OUTPUT CURRENT, IO (A)
6
14
18
12
10
0.5
1
1.5
2
2.5
3
3.5
4
VI = 24 V
VI = 18 V
VI = 36 V
4.5 5
5.5 6 6.5
0.0
1.0
2.0
3.0
0
5
10
15
20
25
OUTPUT CURRENT, IO (A)
4.0
5.0
7.0
6.0
8.0
VI = 18
VI = 28
VI = 36
θca
∆TCmax
,
PD
---------------------
TC
TA
–
()
PD
------------------------
==
00.5
(100)
1.0
(200)
1.5
(300)
2.0
(400)
2.5
(500)
3.0
(600)
0
1
5
6
7
8
AIR VELOCITY MEASURED IN m/s (ft./min.)
4
3
2
1 1/2 IN HEAT SINK
1 IN HEAT SINK
1/2 IN HEAT SINK
1/4 IN HEAT SINK
NO HEAT SINK
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
