BCM4390DKWBGT Datasheet, PDF (74/78 Pages) Cypress Semiconductor – WICED™ Wi-Fi IEEE 802.11 b/g/n SoC with Embedded Application Processor

BCM4390 Advance Data Sheet
Package Information
Section 15: Package Information
Package Thermal Characteristics
Table 26: Package Thermal Characteristics^a
Characteristic
WLCSP
θ_JA (°C/W) (value in still air)
θ_JB (°C/W)
θ_JC (°C/W)
Ψ_JT (°C/W)
Ψ_JB (°C/W)
Maximum Junction Temperature T_j (°C)
Maximum Power Dissipation (W)
33.45
3.45
1.00
3.45
10.64
125
1.119
a. No heat sink, TA = 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 = 1.119W continuous dissipation.
Junction Temperature Estimation and PSI_JT Versus THETA_JC
Package thermal characterization parameter PSI–J_T (Ψ_JT) yields a better estimation of actual junction
temperature (T_J) versus using the junction-to-case thermal resistance parameter Theta–J_C (θ_JC). The reason for
this is that θ_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. Ψ_JT takes into
account power dissipated through the top, bottom, and sides of the package. The equation for calculating the
device junction temperature is:
T_J = T_T + P x Ψ_JT
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)
• Ψ_JT = Package thermal characteristics; no airflow (°C/W)
Environmental Characteristics
For environmental characteristics data, see Table 12: “Environmental Ratings,” on page 56.
BROADCOM ®
February 5, 2014 • 4390-DS103-R
WICED Wi-Fi IEEE 802.11 SoC w/Embedded App Processor
Page 73
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