LM317AMDT National Semiconductor, LM317AMDT Datasheet - Page 10

• Manufacturer Part Number: LM317AMDT
• Description: IC, ADJ LINEAR REG, 1.2V TO 37V, TO252-3
• Manufacturer: National Semiconductor

Specifications of LM317AMDT

• Primary Input Voltage: 40V
• Dropout Voltage Vdo: 2V
• No. Of Outputs: 1
• No. Of Pins: 3
• Output Current: 500mA
• Operating Temperature Range: -40°C To +125°C
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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Application Hints
HEATSINKING THE TO-263 PACKAGE
Figure 7 shows for the TO-263 the measured values of θ
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 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
FIGURE 5. θ
(J−A)
the SOT-223 Package
SOT-223 Package
vs Copper (2 ounce) Area for the
(Continued)
(J−A)
00906357
for the TO-263
00906358
AMB
for
(J−A)
10
As a design aid, Figure 8 shows the maximum allowable
power dissipation compared to ambient temperature for the
TO-263 device (assuming θ
mum junction temperature is 125˚C).
HEATSINKING THE TO-252 PACKAGE
If the maximum allowable value for θ
≥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
As a design aid, Table 1 shows the value of the θ
TO-252 for different heatsink area. The copper patterns that
we used to measure these θ
Application 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
FIGURE 7. θ
2
) for the TO-252 device. Please see AN-1028 for
JA
falls below these limits, a heatsink is required.
(J−A)
the TO-263 Package
vs Copper (1 ounce) Area for the
TO-263 Package
JA
(J−A)
s are shown at the end of the
is 35˚C/W and the maxi-
JA
is found to be
00906355
00906356
AMB
JA
for
of