VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
1.0625 Gbits/sec Fibre
Channel Transceiver
VSC7125
Package Thermal Considerations
The VSC7125 is packaged in either a 10 mm PQFP or a 14 mm PQFP with internal heat spreaders. These
packages use industry-standard EIAJ footprints, but have been enhanced to improve thermal dissipation. The
construction of the packages is as shown in Figure 11.
Figure 11: Package Cross Section
Aluminum Heat Spreader
Plastic Molding Compound
Epoxy
Lead
Bond Wire
Die
Table 5: Thermal Resistance
Symbol
Description
10mm Value
14mm Value
Units
o
θ
θ
Thermal resistance from junction to case
10.5
10
C/W
jc
Thermal resistance from case to ambient in still air including
conduction through the leads.
o
ca
53
32
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
44
39
34
31
28
25
22
20
C/W
ca-100
ca-200
ca-400
ca-600
o
C/W
o
C/W
o
C/W
The VSC7125 is designed to operate with a junction temperature up to 110oC. The user must guarantee that
the temperature specification is not violated. With the Thermal Resistances shown above, the 10x10mm PQFP
can operate in still air ambient temperatures of 53oC [53oC=110oC-0.9W*(10.5oC/W+53oC/W)] while the
14x14 PQFP can operate in still air ambient temperatures of 73oC [73oC=110oC-0.9W*(10oC/W+32oC/W)]. If
the ambient air temperature exceeds these limits then some form of cooling through a heatsink or an increase in
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.
Page 14
VITESSE SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896
G52121-0, Rev. 4.1
4/23/98
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
