LM317SSLASHNOPB datasheet(14/40 Pages) TI1

14 / 40 page

LM117, LM317A, LM317-N

SNVS774O – MAY 2004 – REVISED JANUARY 2014

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As a design aid, Figure 29 shows the maximum allowable power 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).

Figure 29. Maximum Power Dissipation vs TAMB for the TO-263 Package

Heatsinking the TO-252 (NDP) Package

If the maximum allowable value for

θJA is found to be ≥103°C/W (Typical Rated Value) for the TO-252 package,

no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements. If the

calculated value for

θJA falls below these limits, a heatsink is required.

As a design aid, Table 1 shows the value of the

θJA of NDP the package for different heatsink area. The copper

patterns that we used to measure these

θJAs are shown in Figure 34. Figure 30 reflects the same test results as

what are in Table 1.

Figure 31 shows the maximum allowable power dissipation vs. ambient temperature for the TO-252 device.

Figure 32 shows the maximum allowable power dissipation vs. copper area (in2) for the TO-252 device. Please

see AN-1028 (literature number SNVA036) for thermal enhancement techniques to be used with SOT-223 and

TO-252 packages.

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LM317S/NOPB Datasheet(PDF) 14 Page - Texas Instruments