Datasheet

LM2940-N, LM2940C
www.ti.com SNVS769H –MAY 2004–REVISED MARCH 2007
Thermal Performance
3-Lead TO-220 4
Thermal Resistance
°C/W
Junction-to-Case, θ
(JC)
3-Lead TO-263 4
3-Lead TO-220
(1)
60
3-Lead TO-263
(1)
80
Thermal Resistance
°C/W
Junction-to-Ambient, θ
(JA)
SOT-223
(1)
174
8-Lead LLP
(1)
35
(1) The maximum allowable power dissipation is a function of the maximum junction temperature, T
J
, the junction-to-ambient thermal
resistance, θ
JA
, and the ambient temperature, T
A
. Exceeding the maximum allowable power dissipation will cause excessive die
temperature, and the regulator will go into thermal shutdown. The value of θ
JA
(for devices in still air with no heatsink) is 60°C/W for the
TO-220 package, 80°C/W for the TO-263 package, and 174°C/W for the SOT-223 package. The effective value of θ
JA
can be reduced
by using a heatsink (see Application Hints for specific information on heatsinking). The value of θ
JA
for the LLP package is specifically
dependent on PCB trace area, trace material, and the number of layers and thermal vias. For improved thermal resistance and power
dissipation for the LLP package, refer to Application Note AN-1187. It is recommended that 6 vias be placed under the center pad to
improve thermal performance.
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