VITESSE

SEMICONDUCTOR CORPORATION

Preliminary Datasheet

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 VITESSE SEMICONDUCTOR CORPORATION

G52239-0, Rev. 3.3

741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896

5/17/00

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 4: Thermal Resistance

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 5: Thermal Resistance with Airflow

Maximum Ambient Temperature without Heatsink

The worst case ambient temperature without use of a heatsink is given by the equation:

where:

θ

Τ

Τ

Symbol

Description

°C/W

Thermal resistance from

junction to case.

1.34

Thermal resistance from case to

ambient with no airflow,

including conduction through

the leads.

25.0

Airflow

θ

100 lfpm

21

200 lfpm

18

400 lfpm

16

600 lfpm

14.5

T

AMAX

()

T

CMAX

()

P

–

MAX

=