VITESSE
SEMICONDUCTOR CORPORATION
Preliminary Data Sheet
OC-48 16:1 SONET/SDH
MUX with Clock Generator
VSC8163
Thermal Considerations
This package has been enhanced with a copper heat slug to provide a low thermal resistance path from the
die to the exposed surface of the heat spreader. The thermal resistance is shown in the following table
Table 4: Thermal Resistance
°C/W
Symbol
Description
θJC
Thermal resistance from junction-to-case.
1.34
Thermal resistance from case-to-ambient with no
airflow, including conduction through the leads.
θCA
25.0
Thermal Resistance with Airflow
Shown in the Table 5 is the thermal resistance with airflow. This thermal resistance value reflects all the
thermal paths including through the leads in an environment where the leads are exposed. The temperature dif-
ference between the ambient airflow temperature and the case temperature should be the worst-case power of
the device multiplied by the thermal resistance.
Table 5: Thermal Resistance with Airflow
Airflow
θ
ca (oC/W)
100 lfpm
200 lfpm
400 lfpm
600 lfpm
21
18
16
14.5
Maximum Ambient Temperature without Heatsink
The worst case ambient temperature without use of a heatsink is given by the equation:
T
= T
– P
θ
A(MAX)
C(MAX)
CA
(MAX)
where:
θ
Τ
Τ
P
Theta case-to-ambient at appropriate airflow
Ambient Air temperature
Case temperature (85 C for VSC8163)
CA
A(MAX)
o
C(MAX)
(MAX)
Power (1.7W for VSC8163)
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
Internet: www.vitesse.com
Page 18
G52216-0, Rev 3.3
01/05/00
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
