PRELIMINARY
CYW54907
19. Thermal Information
19.1 Package Thermal Characteristics
Table 56. Package Thermal Characteristicsa
Characteristic
WLCSP
33.74
5.5
JA (°C/W) (value in still air)
JB (°C/W)
JC (°C/W)
1.74
JT (°C/W)
JB (°C/W)
5.86
11.52
116.7
1.38
Maximum Junction Temperature Tj (°C)
Maximum power dissipation (W)
a. 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.
19.2 Junction Temperature Estimation and PSI Versus THETA
JT
JC
Package thermal characterization parameter PSI–JT (JT) yields a better estimation of actual junction temperature (TJ) versus using
the junction-to-case thermal resistance parameter Theta–JC (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 JT
Where:
■ TJ = Junction temperature at steady-state condition (°C)
■ TT = 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 16: “Environmental Ratings”.
Document Number: 002-19312 Rev. *C
Page 91 of 95
CYPRESS [ CYPRESS ]
