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I'm using this Regulator namely TLV1117-50IDCYR for a project that I'm working on. Aparently everything is working fine with this chip but sometimes I feel it's heating too much and I'm not putting all the load there.

I'm making a regulation from 12V to 5V for a 300mA output current and it will have a 2,1W of power dissipation.
I've checked the datasheet on the page 5 and it says the Junction-to-ambient thermal resistance is 104.3 ºC/w and the Junction-to-case (top) thermal resistance is 53.7 ºC/W.

My doubt is: which parameter should I consider for my case? If it is the second one I am not seeing any problem.

Can you help me on this? Many thank's!

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The thermal resistance of SMT packages is highly dependent on layout and other factors. I suggest you read relevant sections of this application note (AN-1028 Maximum Power Enhancement Techniques for Power Packages) from TI on their SOT-223 package's thermal characteristics. Pay attention to the thickness of copper (2 oz, for example, is much thicker than typical prototype board thickness- might be 1oz or less).

2.1W is not likely practical in that tiny package unless you can heat sink the tab with a big copper area.

Even in a TO-220 case, you should have a heatsink to be able to safely dissipate that amount of power.

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  • \$\begingroup\$ It's not crazy to use a linear regulator with 2W dissipation, just a bit wasteful. If you are struggling with getting it working and are not a masochist, I suggest you either buy a switching module or stay with the linear and add a heatsink. Switching regulators can be tricky if you don't get the layout right. \$\endgroup\$ – Spehro Pefhany May 11 '15 at 17:43
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    \$\begingroup\$ Yes, to avoid that thermal problems i'd rather implement a switched one. It will be more expensive but at least I will not have problems with heating. \$\endgroup\$ – scuba May 11 '15 at 17:48
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    \$\begingroup\$ If you stay at TI products, they usually provide a recommended layout for switching regulators. \$\endgroup\$ – Bence Kaulics May 11 '15 at 18:00
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    \$\begingroup\$ Yes, I know that. It is supposed to be an addition/response to @Spehro Pefhany's comment, "Switching regulators can be tricky if you don't get the layout right." \$\endgroup\$ – Bence Kaulics May 11 '15 at 18:06
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    \$\begingroup\$ Yes, there's already some recommendations and tips on the datasheet for layout. If I follow them carefully it will not be a problem. \$\endgroup\$ – scuba May 11 '15 at 18:11

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