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LM2937ET-2.5 データシート(PDF) 7 Page - National Semiconductor (TI) |
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LM2937ET-2.5 データシート(HTML) 7 Page - National Semiconductor (TI) |
7 / 10 page θ (H−A) is specified numerically by the heatsink manufacturer in the catalog, or shown in a curve that plots temperature rise vs power dissipation for the heatsink. HEATSINKING TO-263 AND SOT-223 PACKAGE PARTS Both the TO-263 (“S”) and SOT-223 (“MP”) packages use a copper plane on the PCB and the PCB itself as a heatsink. To optimize the heat sinking ability of the plane and PCB, solder the tab of the package to the plane. Figure 3 shows for the TO-263 the measured values of θ (J−A) 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 the figure, increasing the copper area beyond 1 square inch produces very little improvement. It should also be observed that the minimum value of θ (J−A) for the TO-263 package mounted to a PCB is 32˚C/W. As a design aid, Figure 4 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 maxi- mum junction temperature is 125˚C). Figure 5 and Figure 6 show the information for the SOT-223 package. Figure 6 assumes a θ (J−A) of 74˚C/W for 1 ounce copper and 51˚C/W for 2 ounce copper and a maximum junction temperature of 125˚C. Please see AN1028 for power enhancement techniques to be used with the SOT-223 package. SOT-223 SOLDERING RECOMMENDATIONS It is not recommended to use hand soldering or wave solder- ing to attach the small SOT-223 package to a printed circuit board. The excessive temperatures involved may cause package cracking. Either vapor phase or infrared reflow techniques are pre- ferred soldering attachment methods for the SOT-223 pack- age. DS100113-20 FIGURE 3. θ (J−A) vs Copper (1 ounce) Area for the TO-263 Package DS100113-21 FIGURE 4. Maximum Power Dissipation vs T AMB for the TO-263 Package DS100113-22 FIGURE 5. θ (J−A) vs Copper (2 ounce) Area for the SOT-223 Package DS100113-23 FIGURE 6. Maximum Power Dissipation vs T AMB for the SOT-223 Package 7 www.national.com |
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同様の説明 - LM2937ET-2.5 |
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