Im currently working on a circuit which operates at high currents. The circuit has an LM317 which requires an efficient heat sink for its operation under such conditions.
Please suggest a suitable heat sink ?
Please suggest a suitable heat sink ?
How much voltage are you dropping?In my circuit, the LM 317 operating conditions are,
max. current = 350 mA for a duration of 20 minutes.
ambient temperature = 50 °C.
I need the thermal resistance and the configuration of the heat sink?
yes it does. A TO-220 with no sink is 60C/W so 3.5W would raise the temp to about 260C with 50C ambient.If it's a TO-220 it doesn't need a heat sink at all.
I see it. I absolutely guarantee that is wrong. It has to be a misprint.Theta J-A with no sink is ballpark 60C/W for any T0-220 or TO-263 package.The datasheet I posted shows 19 C/W for Rja, page 2.
Lot of misprints around. Most data sheets are done by marketing guys. I have no idea who screwed up the one you saw.... but I worked at nat Semi where the original version of the LM317 document was written. They are owned by TI now and that data sheet is the TI version. Probably have idiots doing the data sheets. They laid off all the people who knew what was going on there, including me.It's a common mistake to believe datatsheets. I guess it was my turn to get fooled.
That's why I said it was 60C/W ballpark. Different departments at Nat Sem got slightly different values depending on who took the data, it also varies SLIGHTLY depending on die size of the device inside the package. But 60C/W is about right.The Fairchild datasheet says 81°C/W max. The Onsemi datasheet says 65°C/W. These companies must have hired the guys that TI laid off.
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