LM317AT National Semiconductor, LM317AT Datasheet - Page 11

• Manufacturer Part Number: LM317AT
• Description: IC, ADJ LINEAR REG, 1.2V TO 37V, TO-220
• Manufacturer: National Semiconductor

Specifications of LM317AT

• Primary Input Voltage: 40V
• Output Voltage Adjustable Range: 1.2V To 37V
• Dropout Voltage Vdo: 2V
• No. Of Outputs: 1
• No. Of Pins: 3
• Output Current: 1.5A
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

HEATSINKING THE TO-263 PACKAGE
Figure 7
−A)
ounce copper and no solder mask over the copper area used
for heatsinking.
As shown in
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
shows for the TO-263 the measured values of θ
Figure
(J−A)
7, increasing the copper area beyond 1
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
11
FIGURE 7. θ
As a design aid,
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,
for different heatsink area. The copper patterns that we used
to measure these θ
Notes Section.
are in
Figure 10
vs. ambient temperature for the TO-252 device.
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
Table
2
) for the TO-252 device. Please see AN-1028 for
shows the maximum allowable power dissipation
1.
(J−A)
Figure 9
Figure 8
Table 1
vs Copper (1 ounce) Area for the TO-263
JA
s are shown at the end of the Application
TO-263 Package
reflects the same test results as what
shows the value of the θ
shows the maximum allowable pow-
Package
(J−A)
is 35°C/W and the maximum
JA
is found to be
906355
JA
AMB
906356
www.national.com
of TO-252
Figure 11
for the
≥
103°
JA