LU3X54FT Datasheet, PDF (42/54 Pages) Agere Systems – QUAD-FET (Fast Ethernet Transceiver) for 10Base-T/100Base-TX/FX

LU3X54FT
QUAD-FET for 10Base-T/100Base-TX/FX
Data Sheet
July 2000
Package and Thermal Characteristics
The LU3X54FT is packaged in a 208-pin SQFP, plain plastic package (LU3X54FT-S208) or with an internal heat
spreader (LU3X54FT-HS208). Both packages have identical dimensions and conform to the outline diagram in this
data sheet. The heat spreader package provides enhanced thermal performance with a lower Theta-JC and
Theta-JA.
The LU3X54FT-S208 plain package thermal characteristics can be enhanced with the use of an external heat sink.
When a system designer finds that the die temperature exceeds either their or Lucent’s (125 °C) maximum temper-
ature limit, a heat sink is then often considered. Heat sink fitness for use needs to be determined by the system
user! Each customers’ requirements tend to be unique, determined by the thermal and physical constraints of the
system; among them are cost, required Theta-CA, headroom above package, direction of airflow, preferred method
of attachment, etc. Table 28. provides the thermal characteristics for each package and for the plain package with
an Aavid Thermal Technology 70035B01100 external heat sink. Figure 9 provides a curve of Theta-JA versus air-
flow when using this Aavid heat sink on the plain package. This heat sink is one example of a heat sink that can
work with our LU3X54FT transceiver.
Table 28. Thermal Characteristics
Theta-JC
(top)
Theta-JA (°C/W)
Plain 208SQFP
Plain 208SQFP w/ Heat Sink*
208SQFP w/ Heat Spreader
(°C/W)
20
20
10
0 fpm
26
23.5
16.1
200 fpm
22.6
13.5
13.3
500 fpm
20.9
12
12
Note: The above table is for the LU3X54FT in the 208SQFP style package (die up).
* Aavid 700353B01100.
24.00
22.00
20.00
18.00
16.00
14.00
12.00
10.00
0
100
200 300 400 500 600
AIRFLOW (fpm)
Figure 9. Thermal Characteristics
42
Lucent Technologies Inc.