Data Sheet
March 2008
1212 Lineage Power
18 Vdc to 36 Vdc Input, 15 Vdc Output; 50 W to 100 W
JC050C, JC075C, JC100C Power Modules: dc-dc Converters;
Thermal considerations (continued)
Heat Transfer Without Heat Sinks (continued)
8-1584 (C)
Figure 23. JC100C 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.). 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
C, max) divided by the
module power dissipation (P
D):
The location to measure case temperature (T
C) is
shown in Figure 20. Case-to-ambient thermal resis-
tance vs. airflow is shown, for various heat sink config-
urations and heights, in Figure 24. These curves were
obtained by experimental testing of heat sinks, which
are offered in the product catalog.
8-1153
Figure 24. 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 Figure 24 had a
thermal-conductive dry pad between the case and the
heat sink to minimize contact resistance. The use of
Figure 24 is shown in the following example
Example
If an 85 °C case temperature is desired, what is the
minimum airflow necessary? Assume the JC100C
module is operating at nominal line and an output cur-
rent of 6 A, maximum ambient air temperature of
40 °C, and the heat sink is 0.5 in.
14
6
1 2 3 54 6
0
12
OUTPUT CURRENT, IO (A)
8
10
4
2
16
70
POWER DISSIPATION, PD (W)
18
VI = 18 V
VI = 28 V
VI = 36 V
θca
ΔTCmax,
PD
---------------------
T
C TA–()
P
D
------------------------
==
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
CASE-TO-AMBIENT THERMAL
RESISTANCE, RCA (°C/W)
1 1/2 IN HEAT SINK
1 IN HEAT SINK
1/2 IN HEAT SINK
1/4 IN HEAT SINK
NO HEAT SINK
