TS39150 Datasheet, PDF (4/5 Pages) Taiwan Semiconductor Company, Ltd – 1.5A Ultra Low Dropout Fixed Positive Voltage Regulator

Application Information (continues)
Using the calculated values for T_R(max) and P_D, the
maximum allowable value for the junction to ambient
thermal resistance, θja, can now be found:
θja = T_R(max) / P_D
IMPORTANT: if the maximum allowable value for is
found to be ≥60 ^oC/W for the TO-220 package, ≥80
o_{C/W for the TO-263 package, no heatsink is needed}
since the package alone will dissipate enough heat to
satisfy these requirements. If the calculated value for
θja falls below these limits, a heatsink is required.
TS39150
4-5
2005/3 rev. A