Lineage Power 11
Data Sheet
March 2008 18 Vdc to 36 Vdc Input, 3.3 Vdc Output; 33 W to 66 W
JC050F, JC075F, JC100F Power Modules: dc-dc Converters;
Thermal Considerations
Introduction
The power modules operate in a variety of thermal
environments; however, sufficient cooling should be
provided to help ensure reliable operation of the unit.
Heat-dissipating components inside the unit are ther-
mally coupled to the case. Heat is removed by conduc-
tion, convection, and radiation to the surrounding
environment. Proper cooling can be verified by mea-
suring the case temperature. Peak temperature (Tc)
occurs at the position indicated in Figure 22.
8-716 f
Note: Top view, pin locations are for reference.
Measurements shown in millimeters and (inches).
Figure 22. Case Temperature Measurement
Location
The temperature at this location should not exceed
100 °C. The output power of the module should not
exceed the rated power for the module as listed in the
Ordering Information table.
Although the maximum case temperature of the power
modules is 100 °C, you can limit this temperature to a
lower value for extremely high reliability.
For additional information on these modules, refer to the
Thermal Management JC-, JFC-, JW-, and JFW-Series
50 W to 150 W Board-Mounted Power Modules Technical
Note (TN97-008EPS).
Heat Transfer Without Heat Sinks
Increasing airflow over the module enhances the heat
transfer via convection. Figure 23 shows the maximum
power that can be dissipated by the module without
exceeding the maximum case temperature versus local
ambient temperature (T
A) for natural convection
through 4 m/s (800 ft./min.).
Note that the natural convection condition was mea-
sured at 0.05 m/s to 0.1 m/s (10 ft./min. to 20 ft./min.);
however, systems in which these power modules may
be used typically generate natural convection airflow
rates of 0.3 m/s (60 ft./min.) due to other heat dissipat-
ing components in the system. The use of Figure 23 is
shown in the following example.
Example
What is the minimum airflow necessary for a JC100F
operating at nominal line, an output current of 20 A,
and a maximum ambient temperature of 40 °C?
Solution
Given: V
I = 28 V
I
O = 20 A
T
A = 40 °C
Determine P
D (Use Figure 26.):
P
D = 18.2 W
Determine airflow (v) (Use Figure 23.):
v = 2.3 m/s (450 ft./min.)
8-1150 a
Figure 23. Forced Convection Power Derating with
No Heat Sink; Either Orientation
38.0 (1.50)
MEASURE CASE
V
I(–)
ON/OFF
CASE
+ SEN
TRIM
– SEN
V
I(+)
V
O(–)
V
O(+)
7.6 (0.3)
TEMPERATURE HERE
0 10203040 10
0
35
LOCAL AMBIENT TEMPERATURE, T
A (˚C)
POWER DISSIPATION, PD (W)
25
20
10
90
80706050
4.0 m/s (800 ft./min.)
0.1 m/s (NAT. CONV.)
(20 ft./min.)
0.5 m/s (100 ft./min.)
1.0 m/s (200 ft./min.)
1.5 m/s (300 ft./min.)
2.0 m/s (400 ft./min.)
2.5 m/s (500 ft./min.)
3.0 m/s (600 ft./min.)
3.5 m/s (700 ft./min.)
5
15
30
