VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
1.0625 Gb/s Fibre Channel
Dual Repeater / Hub Node
VSC7140
Package Thermal Characteristics
The VSC7140 is packaged into a thermally-enhanced plastic quad flatpack. This package adheres to the
industry-standard EIAJ footprint for a 10x10mm body but has been enhanced to improve thermal dissipation
with the inclusion of an exposed copper heat spreader. The package construction is as shown in Figure 6.
Figure 6: Package Cross Section
Copper Heat Spreader
Insulator
Lead
Wire Bond
Plastic Molding Compound
Die
The thermal resistance for the VSC7140 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 leadframe through the heat spreader
overlap of the leadframe.
Table 3: 52 PQFP Thermal Resistance
Symbol
Description
Thermal resistance from junction to case
Value
Units
oC/W
θjc
2.5
Thermal resistance from case to ambient in still air including conduction through
the leads for a non-thermally saturated board.
θca
37.0
oC/W
oC/W
oC/W
oC/W
oC/W
θca-100
θca-200
θca-400
θca-600
Thermal resistance from case to ambient in 100 LFPM air.
Thermal resistance from case to ambient in 200 LFPM air.
Thermal resistance from case to ambient in 400 LFPM air.
Thermal resistance from case to ambient in 600 LFPM air.
31.0
28.0
24.0
22.0
o
The user must ensure that the maximum case temperature specification (95 C) is not exceeded. Given the
thermal resistance of the package in still air, the user may operate the VSC7140 in still air if the ambient tem-
o
perature does not exceed 32o C (95 C - 1.7W * 37o C/W = 32o C). If operation above this ambient temperature
is required, an appropriate heatsink must be used with the part or adequate airflow must be provided.
Moisture Sensitivity Level
This device is rated with a moisture sensitivity level 3 rating. Refer to Application Note AN-20 for appro-
priate handling procedures.
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
G52180-0, Rev 4.0
10/23/00
Page 11
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
Internet: www.vitesse.com
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