11.3 Thermal Considerations

The maximum device junction temperature must be restricted to 125°C under normal operating conditions. This restriction limits the power dissipation of the TPS61165. Calculate the maximum allowable dissipation, P_D(max), and keep the actual dissipation less than or equal to P_D(max). The maximum-power-dissipation limit is determined using Equation 8:

Equation 8.

where

• T_A is the maximum ambient temperature for the application
• R_θJA is the thermal resistance junction-to-ambient given in Thermal Information

The TPS61165 comes in a thermally enhanced QFN package. This package includes a thermal pad that improves the thermal capabilities of the package. The R_θJA of the QFN package greatly depends on the PCB layout and thermal pad connection. The thermal pad must be soldered to the analog ground on the PCB. Using thermal vias underneath the thermal pad as illustrated in the layout example. Also see the QFN/SON PCB Attachment application report (SLUA271).