LM317SSLASHNOPB datasheet(31/48 Pages) TI1

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LM117, LM317-N

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SNVS774P – MAY 2004 – REVISED OCTOBER 2015

Thermal Considerations (continued)

Figure 42. Maximum Power Dissipation vs TAMB for the TO-263 Package

11.3.2.3 Heatsinking the TO-252 (NDP) Package

If the maximum allowable value for

θJA is found to be ≥ 54°C/W (typical rated value) for the TO-252 package, no

heatsink is needed because 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 2 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 47. Figure 43 reflects the same test results as

what are in Table 2.

Figure 44 shows the maximum allowable power dissipation versus ambient temperature for the TO-252 device.

Figure 45 shows the maximum allowable power dissipation versus copper area (in2) for the TO-252 device. See

AN-1028 (SNVA036) for thermal enhancement techniques to be used with SOT-223 and TO-252 packages.

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LM317S/NOPB 数据表(PDF) 31 Page - Texas Instruments