BCM89359 Advance Data Sheet
Package Information
Section 20: Package Information
Package Thermal Characteristics
The information in Table 59 is based on the following conditions:
•
•
No heat sink, T = 70°C. This is an estimate, based on a 4-layer PCB that conforms to EIA/JESD51–7
(101.6 mm × 101.6 mm × 1.6 mm) and P = 2.65W continuous dissipation.
A
Absolute junction temperature limits are maintained through active thermal monitoring or turning off one of
the TX chains, or both.
Table 59: WLBGA Package Thermal Characteristics
Characteristic
JA (°C/W) (value in still air)
JB (°C/W)
WLBGA
39.1
4.51
1.24
6.53
11.6
JC (°C/W)
(°C/W)
JT
JB
(°C/W)
Maximum Junction Temperature T (°C)
125
j
Maximum Power Dissipation (W)
2.65
Junction Temperature Estimation and PSIJT Versus ThetaJC
The package thermal characterization parameter PSI ( ) yields a better estimation of actual junction
JT
JT
temperature (T ) than using the junction-to-case thermal resistance parameter Theta (JC). The reason for
J
JC
this is that JC is based on the assumption that all the power is dissipated through the top surface of the package
case. In actual applications, however, some of the power is dissipated through the bottom and sides of the
package. takes into account the power dissipated through the top, bottom, and sides of the package. The
JT
equation for calculating the device junction temperature is:
TJ = TT + P x JT
Where:
•
•
•
•
T = Junction temperature at steady-state condition (°C)
J
T = Package case top center temperature at steady-state condition (°C)
T
P = Device power dissipation (Watts)
= Package thermal characteristics; no airflow (°C/W)
JT
Broadcom®
September 9, 2014 • 89359-DS100-R
Page 147
BROADCOM CONFIDENTIAL
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