Datasheet

LM340-N, LM78xx
www.ti.com SNOSBT0J –FEBRUARY 2000–REVISED DECEMBER 2013
Operating Conditions
(1)
(continued)
LM140 −55°C to +125°C
Temperature Range (T
A
)
(2)
LM340A, LM340-N 0°C to +125°C
LM7808C 0°C to +125°C
(2) The maximum allowable power dissipation at any ambient temperature is a function of the maximum junction temperature for operation
(T
JMAX
= 125°C or 150°C), the junction-to-ambient thermal resistance (θ
JA
), and the ambient temperature (T
A
). P
DMAX
= (T
JMAX
−
T
A
)/θ
JA
. If this dissipation is exceeded, the die temperature will rise above T
JMAX
and the electrical specifications do not apply. If the die
temperature rises above 150°C, the device will go into thermal shutdown. For the TO-3 package (NDS), the junction-to-ambient thermal
resistance (θ
JA
) is 39°C/W. When using a heatsink, θ
JA
is the sum of the 4°C/W junction-to-case thermal resistance (θ
JC
) of the TO-3
package and the case-to-ambient thermal resistance of the heatsink. For the TO-220 package (NDE), θ
JA
is 54°C/W and θ
JC
is 4°C/W. If
SOT-223 is used, the junction-to-ambient thermal resistance is 174°C/W and can be reduced by a heatsink (see Applications Hints on
heatsinking).If the DDPAK\TO-263 package is used, the thermal resistance can be reduced by increasing the PC board copper area
thermally connected to the package: Using 0.5 square inches of copper area, θ
JA
is 50°C/W; with 1 square inch of copper area, θ
JA
is
37°C/W; and with 1.6 or more inches of copper area, θ
JA
is 32°C/W.
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