LT3080 in through-hole

[steff]

Since Dave's gone into such depth with it, I thought I'd have a go at building his bench PSU design. I'm running into slight problems finding LT3080s (in the UK) in through-hole packaging though. The only place I can find them is Digikey (http://search.digikey.com/uk/en/products/LT3080ET%23PBF/LT3080ET%23PBF-ND/1768180) who want £12 shipping for a small order and an eBay seller that wants £7+/part. Places like Farnell only seem to have SMT variants.

All this makes me a bit nervous - ideally I'd prefer to use parts that are readily obtainable from multiple places. Or am I failing at searching for it (I'm very new to this game)? Or is there perhaps some substitute part that's commoner over here?

[veryevil]

Sucks when thats the case. Best bet is Free Samples!

http://www.linear.com/samples/LT3080

[steff]

Oh, excellent point 

Doesn't really help with the "what if I want to get hold of some more of these" issue but hey, free's free.

I've put in for a couple of LT3083s and some voltage references too - might well be useful in this or related applications. If I get the thing working, I'll stick a writeup on here for the general delight and with luck Linear will sell a few extra and cover their seed capital, as it were.

[joelby]

Don't be scared of SMT parts! The SOT223-3 package isn't too small, and you might be able to find a breakout board for it - here's one for $1.27.

[EEVblog]

You can always use an LM317, you just have to live with the 1.25V offset and minimum for the signal supply configuration.

Dave.

[Rufus]

Don't be scared of SMT parts! The SOT223-3 package isn't too small

As the main pass element in a power supply it is too small for power dissipation. The SOT-223 package has 1/5th the dissipation capability of the TO-220 package and that is ignoring the difficulty of heat sinking it.

[metalphreak]

If you want to go surface mount, just get the DPAK style instead.

http://au.element14.com/linear-technology/lt3080eq-pbf/ic-adj-ldo-reg-0v-to-36v-1-1a-d2/dp/1761436

All the various packages are capable of 1.1A, but you'd only use the SOT223 and other small SMD packages when you have a lower voltage differential between input and output. Trying to regulate 36V down to 5v @ 1A with a SOT223    30+ Watts of dissipation! (this is also why large voltage range supplies use transformers with multiple voltage taps)

http://cds.linear.com/docs/Datasheet/3080fc.pdf

Check out the design considerations section for information about heat dissipation using the PCB.

Best case for SOT223 is 48°C/W while the DD PAK is 25°C/W (Junction to Ambient)

TO220 is  3°C/W Junction to Case, add on to this value the rating for your heatsink.

[steff]

Cheers chaps/Dave. I've just got the email through from Linear saying it'll be about two weeks but the samples are coming, so it looks like it'll be all right.

[steff]

A colleague informs me that they're on my desk at work. If anyone for Linear is reading this, thanks!

[Stephen Hill]

I just want to say that I too ordered some sample LT3080's in a TO-220 package from LT which arrived here in the UK within 6days

[PStevenson]

Oh, excellent point 

Doesn't really help with the "what if I want to get hold of some more of these" issue but hey, free's free.

if you want to get hold of more of them just request free samples again!

[amateur_25]

Sucks when thats the case. Best bet is Free Samples!

http://www.linear.com/samples/LT3080

I just want to thank you for your suggestion. I live in the uk. Getting some of these electronics parts is royal pain in the butt. I have no choice but to go to the biggest
distruibutor I know of Farnell. But they charge £15!! for us stock!! Not really worth it for a one off thing. I didn't think they would do it since I only wanted 2.
It was ovious I won't be ordering any more as well.

[Armin_Balija]

I actually ordered free samples of the LT3080, TLC2272 and I just need to order the LT1009. So far the only thing I've bought is the LM334 and the discrete components. I'm also going to need to buy a two 10 turn pots because I can't seem to find any place that would give out a free sample of such an expensive part. Linear Technology, NS, and TI, and others will give free samples so don't hesitate to try them out. Don't overdo it though because it's kind of rude. I only ordered how much I needed, not going to abuse the system. If I like it I might try altering the design a bit and see what I can do by buying the parts.

Anyway, free samples are great. Have at it.