LM117H-MW8 National Semiconductor Corporation, LM117H-MW8 Datasheet - Page 10

• Manufacturer Part Number: LM117H-MW8
• Description: 3-terminal Adjustable Regulator
• Manufacturer: National Semiconductor Corporation

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HEATSINKING THE TO-263 PACKAGE
Figure 7 shows for the TO-263 the measured values of θ
−A)
ounce copper and no solder mask over the copper area used
for heatsinking.
As shown in Figure 7, increasing the copper area beyond 1
square inch produces very little improvement. It should also
be observed that the minimum value of θ
package mounted to a PCB is 32°C/W.
FIGURE 6. Maximum Power Dissipation vs T
for different copper area sizes using a typical PCB with 1
FIGURE 5. θ
(J−A)
SOT-223 Package
SOT-223 Package
vs Copper (2 ounce) Area for the
(J−A)
for the TO-263
906357
906358
AMB
for the
(J
10
FIGURE 7. θ
As a design aid, Figure 8 shows the maximum allowable pow-
er dissipation compared to ambient temperature for the
TO-263 device (assuming θ
junction temperature is 125°C).
HEATSINKING THE TO-252 PACKAGE
If the maximum allowable value for θ
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
falls below these limits, a heatsink is required.
As a design aid, Table 1 shows the value of the θ
for different heatsink area. The copper patterns that we used
to measure these θ
Notes Section. Figure 9 reflects the same test results as what
are in Table 1.
Figure 10 shows the maximum allowable power dissipation
vs. ambient temperature for the TO-252 device. Figure 11
shows the maximum allowable power dissipation vs. copper
area (in
thermal enhancement techniques to be used with SOT-223
and TO-252 packages.
FIGURE 8. Maximum Power Dissipation vs T
2
) for the TO-252 device. Please see AN-1028 for
(J−A)
vs Copper (1 ounce) Area for the TO-263
JA
s are shown at the end of the Application
TO-263 Package
Package
(J−A)
is 35°C/W and the maximum
JA
is found to be
906355
JA
906356
AMB
of TO-252
for the
≥
103°
JA