VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC8117

ATM/SONET/SDH 622/155 Mb/s Transceiver Mux/Demux

with Integrated Clock Generation and Clock Recovery

Page 18

© VITESSE SEMICONDUCTOR CORPORATION

G52221-0, Rev 4.1

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

1/8/00

Package Thermal Characteristics

The VSC8117 is packaged into a thermally-enhanced plastic quad flatpack (PQFP). This package adheres

to the industry-standard EIAJ footprint for a 10x10mm body but has been enhanced to improve thermal dissipa-

tion with the inclusion of an exposed Copper Heat Spreader. The package construction is as shown in Figure 10.

Figure 11: Package Cross Section

The thermal resistance for the VSC8117 package is improved through low thermal resistance paths from

the die to the exposed surface of the heat spreader and from the die to the lead frame through the heat spreader

overlap of the lead frame.

Table 16: 64-Pin PQFP Thermal Resistance

antee that the maximum case temperature specification is not violated. Given the thermal resistance of the pack-

age in still air, the user can operate the VSC8117QB1 in still air if the ambient temperature does not exceed

priate heatsink must be used with the part or adequate airflow must be provided.

Symbol

Description

Value

Units

θ

jc

Thermal resistance from junction to case

2.5

θ

ca

Thermal resistance from case to ambient in still air including conduction through

the leads for a non-thermally saturated board.

37

θ

ca-100

Thermal resistance from case to ambient in 100 LPFM air

31

θ

ca-200

Thermal resistance from case to ambient in 200 LPFM air

28

θ

ca-400

Thermal resistance from case to ambient in 400 LPFM air

24

θ

ca-600

Thermal resistance from case to ambient in 600 LPFM air

22

Lead

Copper Heat Spreader

Die

Plastic Molding Compound

Insulator

Wire Bond