VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
Multi-Rate SONET/SDH
VSC8122
Clock and Data Recovery IC
Package 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 9: Thermal Resistance
Symbol
Description
oC/W
θ-jc
Thermal resistance from junction to case.
1.5
Thermal resistance from case to ambient with no airflow,
including conduction through the leads.
θ-ca
31.5
Thermal Resistance With Airflow
Shown in the table below 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 10: Thermal Resistance With Airflow
Airflow
θ-ca (oC/W)
100 lfpm
200 lfpm
400 lfpm
600 lfpm
25.8
23.0
19.3
17.0
Maximum Ambient Temperature Without Heatsink
The worst case ambient temperature without use of a heatsink is given by the equation:
TA(MAX) = TC(MAX) - P(MAX) CA
θ
where:
= Theta case to ambient at appropriate airflow
θ
T
T
CA
= Ambient Air temperature
= Case temperature (85oC for VSC8122)
A(MAX)
C(MAX)
P
= Power (1.2W for VSC8122)
(MAX)
© 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 12
G52228-0, Rev 4.1
01/05/01
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
