9.1 Power Dissipation and Junction Temperature

Specified regulator operation is assured to a junction temperature of 125°C; the maximum junction temperature allowable to avoid damaging the device is 150°C. This restriction limits the power dissipation the regulator can handle in any given application. To ensure the junction temperature is within acceptable limits, calculate the maximum allowable dissipation, P_D(max), and the actual dissipation, P_D, which must be less than or equal to P_D(max).

The maximum-power-dissipation limit is determined using Equation 3.

Equation 3.

where

• T_Jmax is the maximum allowable junction temperature
• R_θJA is the thermal resistance junction-to-ambient for the package, see Thermal Information
• T_A is the ambient temperature

The regulator dissipation is calculating using Equation 4.

Equation 4.

Power dissipation resulting from quiescent current is negligible.