VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
ATM/SONET/SDH 622/155 Mb/s Transceiver Mux/Demux
with Integrated Clock Generation and Clock Recovery
VSC8117
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
Copper Heat Spreader
Insulator
Lead
Wire Bond
Plastic Molding Compound
Die
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
Symbol
Description
Thermal resistance from junction to case
Value
Units
oC/W
2.5
θjc
Thermal resistance from case to ambient in still air including conduction through
the leads for a non-thermally saturated board.
θca
37
oC/W
θca-100
θca-200
θca-400
θca-600
Thermal resistance from case to ambient in 100 LPFM air
Thermal resistance from case to ambient in 200 LPFM air
Thermal resistance from case to ambient in 400 LPFM air
Thermal resistance from case to ambient in 600 LPFM air
31
28
24
22
oC/W
oC/W
oC/W
oC/W
o
The VSC8117QB1 is designed to operate at a maximum case temperature of up to 115 C. The user must guar-
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
o
o
o
o
55 C (55 C = 115 C - 1.6W * 37 C/W). If operation above this ambient temperature is required, then an appro-
priate heatsink must be used with the part or adequate airflow must be provided.
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
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
