SMT LM317's current limit, can it be raised by heatsinking?

Question

I want 1.5A, but the TO-220 and TO-263 packs are too fat for the space I'm working with. I could gang more than one part but I want to avoid that.

Two SMT parts have the right size for the narrow space they must fit into:

LM317MDT TO-252 0.5A LM317EMP SOT-223 1.0A

Can either of these be safely pushed to do 1.5 amps if soldered to a copper slab with their legs raised clear? I have no trouble getting the heat away from them, my limiting point is that I don't know if there is a difference in the internal structure size between these and the 1.5A rated parts, or if it's impossible to make what's in the SMT types carry that much current, given enough heatsinking.

Lostgallifreyan · Accepted Answer

Andy  wrote in news:456985b2$0$29840$Nice. Found a KTE type in the TI datasheet too. National Semiconductors didn't tell me about either of these.The question still stands though. The package rating probably assumes maximum thermal coupling in intended mountings, so could a 1A or even a 0.5A device manage 1.5A if directly soldered to a copper bar or slab? If there is no difference in the chip inside it, my guess is it can, but is there a difference, or do they only differ in the way the chips are packaged?

Andy · Answer

LM317DCY

Andy · Answer

There is an electrical difference, and it is reflected in the datasheet.    These chips have built-in current limiting.

Lostgallifreyan · Answer

Andy  wrote in news:4569b4c1$0$21902$Thanks, I'd forgotten that, thought it was only over-temperature shutdown.

SMT LM317's current limit, can it be raised by heatsinking?

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