VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC8061/VSC8062

2.5Gb/s 16-Bit

Multiplexer/Demultiplexer Chipset

Page 16

G52069-0, Rev 4.3

05/11/01

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Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com

Internet: www.vitesse.com

Thermal Considerations

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

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

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

Symbol

Description

F Pack

QH Pack

Units

Thermal resistance from junction-to -case.

1.3

2.1

°C/W

Thermal resistance from case-to-ambient still air including

conduction through the leads.

18.5

30.0

°C/W

Airflow

Units

100 lfpm

15.9

24

200 lfpm

14.9

21

300 lfpm

14.2

19

500 lfpm

13.3

15