By using the thermal metrics Ψ_JT and Ψ_JB, as shown in the Section 6.4 table, the junction temperature can be estimated with corresponding formulas (given in Equation 6). For backwards compatibility, an older θ_JC(top) parameter is listed as well.

Equation 6.

where:

• P_D is the power dissipation
• T_T is the temperature at the center-top of the package
• T_B is the PCB temperature measured 1 mm away from the package on the PCB surface

For more information about measuring T_T and T_B, see the Using New Thermal Metrics application note, available for download at www.ti.com.

For a more detailed discussion of why TI does not recommend using θ_JC(top) to determine thermal characteristics, see the Using New Thermal Metrics application note, available for download at www.ti.com. For further information, see the Semiconductor and IC Package Thermal Metrics application note, also available on the TI website.