VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
10-Bit Transceiver for Fibre
Channel and Gigabit Ethernet
VSC7123
Package Thermal Considerations
The VSC7123 is packaged in a 14mm, thermally-enhanced PQFP with an internal heat spreader a 10 mm,
thermally enhanced PQFP and a 10mm cavity-down, exposed pad TQFP. These packages use industry-standard
EIAJ footprints, but have been enhanced to improve thermal dissipation. The construction of the packages is
shown in Figure 10.
Figure 10: PQFP Package Cross Section
Internal Heat Spreader
Plastic Molding Compound
Insulator
Lead
Die
Bond Wire
Table 6: Thermal Resistance
10mm
PQFP
14mm
PQFP
10mm
TQFP
Symbol
Description
Units
oC/W
oC/W
θjc
Thermal resistance from junction-to-case
10
50
9.5
7.0
40
θca
Thermal resistance from case-to-ambient in still air including
conduction through the leads.
29
oC/W
oC/W
oC/W
oC/W
θca-100
θca-200
θca-400
θca-600
Thermal resistance from case-to-ambient with 100 LFM airflow
Thermal resistance from case-to-ambient with 200 LFM airflow
Thermal resistance from case-to-ambient with 400 LFM airflow
Thermal resistance from case-to-ambient with 600 LFM airflow
41
37
32
28
26
24
21
18
38
35
33
30
o
The VSC7123 is designed to operate with a case temperature up to 95 C. The user must guarantee that the
case temperature specification is not violated. With the thermal resistances shown in Table 7, the 10mm
o
o
o
thermally-enhanced PQFP package can operate in still air ambient temperatures of 50 C [50 C = 95 C - 0.9W *
o
50 C/W]. The 14mm thermally-enhanced PQFP package can operate in still air ambient temperatures of 69 C
[69 C = 95 C - 0.9W * 29 C/W]. The TQFP package can operate in a still air ambient temperature of 59 C
[59 C = 95 C - 0.9W * 40 C/W]. If the ambient air temperature exceeds these limits, a form of cooling through
a heatsink or an increase in airflow must be provided.
o
o
o
o
o
Moisture Sensitivity Level
This device is rated at a Moisture Sensitivity Level 3 rating with maximum floor life of 168 hours at 30ºC,
60% relative humidity. Please refer to Application Note AN-20 for appropriate handling procedures.
G52212-0, Rev 4.3
03/25//01
Page 17
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