VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
2.5Gb/s 16-Bit
Multiplexer/Demultiplexer Chipset
VSC8061/VSC8062
Thermal Cons iderations
The VSC8061 and VSC8062 are available in ceramic LDCC and thermally enhanced plastic quad flat-
packs. These packages have been enhanced to improve thermal dissipation through low thermal resistance paths
from the die to the exposed surface of the heat spreader. The thermal resistance of the two packages is shown in
the following table
Table 9: Thermal Resistance
Symbol
Description
F Pack
1.3
QH Pack
2.1
Units
qJC
Thermal resistance from junction-to -case.
°C/W
°C/W
Thermal resistance from case-to-ambient still air including
conduction through the leads.
qCA
18.5
30.0
Thermal Resistance with Airflow
Shown in Table 10 is the thermal resistance with airflow. This thermal resistance value reflects all the ther-
mal paths including through the leads in an environment where the leads are exposed. The temperature differ-
ence between the ambient airflow temperature and the case temperature should be the worst case power of the
device multiplied by the thermal resistance.
Table 10: Thermal Resistance with Airflow
Airflow
qCA for F Package
qCA for QH Package
Units
100 lfpm
200 lfpm
300 lfpm
500 lfpm
15.9
14.9
14.2
13.3
24
21
19
15
oC/W
oC/W
oC/W
oC/W
Thermal Resistance with Heat Sink
The determination of appropriate heat sink to use is as shown below, using the VSC8061 in QH package as
an example.
Figure 11: VSC8061 in QH Package
T
A
qSA
qCS
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Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
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Page 16
G52069-0, Rev 4.3
05/11/01
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