VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
1.25Gbits/sec
Gigabit Ethernet Transceiver
VSC7135
Package Thermal Considerations
The VSC7135 is packaged in a 14 mm conventional PQFP with an internal heat spreader. This package use
an industry-standard EIAJ footprint, but have been enhanced to improve thermal dissipation. The construction
of the packages are as shown in Figure 12.
Figure 10: Package Cross Section - 14 mm package
Copper Heat Spreader
Plastic Molding Compound
Lead
Table 5: Thermal Resistance
Die
Bond Wire
Symbol
Description
Thermal resistance from junction to case
10mm Value
14mm Value
Units
o
θ
θ
10.0
9.5
C/W
jc
Thermal resistance from case to ambient in still air including
conduction through the leads.
o
ca
50.8
29
C/W
o
θ
θ
θ
θ
Thermal resistance from case to ambient with 100 LFM airflow
Thermal resistance from case to ambient with200 LFM airflow
Thermal resistance from case to ambient with 400 LFM airflow
Thermal resistance from case to ambient with 600 LFM airflow
41.2
36.9
31.8
27.8
26.1
23.8
20.5
17.9
C/W
ca-100
ca-200
ca-400
ca-600
o
C/W
o
C/W
o
C/W
The VSC7135 is designed to operate with a junction temperature up to 105oC. The user must guarantee that
the temperature specification is not violated. With the Thermal Resistances shown above, the 10x10 PQFP can
operate in still air ambient temperatures of 55oC [55oC=110oC-0.9W*(10oC/W+50.8oC/W)] while the 14x14
PQFP can operate in still air ambient temperatures of 75oC [75oC=110oC-0.9W*(9.5oC/W+29oC/W)]. If the
ambient air temperature exceeds these limits then some form of cooling through a heatsink or an increase in air-
flow 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.
Page 14
VITESSE SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896
G52146-0, Rev. 4.0
5/28/98
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
