Document Number: 002-14826 Rev. *G
Page 61 of 65
PRELIMINARY
CYW43903
19. Thermal Information
19.1 Package Thermal Characteristics
19.2 Junction Temperature Estimation and PSI
JT
Versus THETA
JC
Package thermal characterization parameter PSI–J
T
(
JT
) yields a better estimation of actual junction temperature (T
J
) versus using
the junction-to-case thermal resistance parameter Theta–J
C
(
JC
). The reason for this is that
JC
assumes that all the power is
dissipated through the top surface of the package case. In actual applications, some of the power is dissipated through the bottom
and sides of the package.
JT
takes into account power dissipated through the top, bottom, and sides of the package. The equation
for calculating the device junction temperature is:
TJ = TT + P x YJT
Where:
■
T
J
= Junction temperature at steady-state condition (°C)
■
T
T
= Package case top center temperature at steady-state condition (°C)
■
P = Device power dissipation (Watts)
■
JT
= Package thermal characteristics; no airflow (°C/W)
19.3 Environmental Characteristics
For environmental characteristics data, see
Table 14, “Environmental Ratings,”
.
Table 32. Package Thermal Characteristics
1
1. No heat sink, TA = 70°C. This is an estimate based on a 4-layer PCB that conforms to EIA/JESD51–7. Air velocity is 0 m/s.
Characteristic
WLBGA
JA
(°C/W) (value in still air)
31.72
JB
(°C/W)
3.95
JC
(°C/W)
2.16
JT
(°C/W)
4.3
JB
(°C/W)
9.28
Maximum Junction Temperature T
j
(°C)
113.9
Maximum power dissipation (W)
1.38
