LM117/LM317A/LM317
906357
906355
FIGURE 5.
θ
(J−A)
vs Copper (2 ounce) Area for the
SOT-223 Package
FIGURE 7.
θ
(J−A)
vs Copper (1 ounce) Area for the TO-263
Package
As a design aid,
shows the maximum allowable pow-
er dissipation compared to ambient temperature for the
TO-263 device (assuming
θ
(J−A)
is 35°C/W and the maximum
junction temperature is 125°C).
906358
FIGURE 6. Maximum Power Dissipation vs T
AMB
for the
SOT-223 Package
HEATSINKING THE TO-263 PACKAGE
shows for the TO-263 the measured values of
θ
(J
−A)
for different copper area sizes using a typical PCB with 1
ounce copper and no solder mask over the copper area used
for heatsinking.
As shown in
increasing the copper area beyond 1
square inch produces very little improvement. It should also
be observed that the minimum value of
θ
(J−A)
for the TO-263
package mounted to a PCB is 32°C/W.
906356
FIGURE 8. Maximum Power Dissipation vs T
AMB
for the
TO-263 Package
HEATSINKING THE TO-252 PACKAGE
If the maximum allowable value for
θ
JA
is found to be
≥
103°
C/W (Typical Rated Value) for TO-252 package, no heatsink
is needed since the package alone will dissipate enough heat
to satisfy these requirements. If the calculated value for
θ
JA
falls below these limits, a heatsink is required.
As a design aid,
shows the value of the
θ
JA
of TO-252
for different heatsink area. The copper patterns that we used
to measure these
θ
JA
s are shown at the end of the Application
Notes Section.
reflects the same test results as what
are in
shows the maximum allowable power dissipation
vs. ambient temperature for the TO-252 device.
shows the maximum allowable power dissipation vs. copper
area (in
2
) for the TO-252 device. Please see AN-1028 for
thermal enhancement techniques to be used with SOT-223
and TO-252 packages.
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