voltage regulator help - ot

[docwisdom]

Sorry for the OT message, but you guys are great at answering my questions, and pretty quick at it.

Right now I am using LM317 voltage regulators to power my mosfets because each color of my RGB LED requires a separate voltage. The LM317 is only 1.5 amps & I would love to go up to the LM350 which is 3 amps. My main problem is that the heat generated by either one is enough that it requires a heatsink. I am using an aluminum enclosure and would love to bolt to it as a heatsink, but the tab shares output voltage which would cause problems with the grounded case.

Could anyone recommend other adjustable voltage regulators that might solve these problems? I see that the LM2650 doesnt require a heatsink, but it is SOIC and right now I am prototyping with all through hole stuff.

Anyway, I have only been working in the IC world for a few months now, so if anyone could shine some light on other magic IC's It would be great. Diging through the Digi-Key and Mouser catalogs is pretty tedious.

much thanks

brian

[Travin77]

Why not change to a plastic case? You can buy them at radioshack for about $3 and can get some pretty large ones.

[mister_e]

Why not changing for a plastic case??? Probably because the plastic case will never sink (dissipate ... i don't know the translation... bah anyway) any heat. So useless in this case.

There's still some insulator kit for most package to avoid that in case you really want to screw the regulator on the metal casing. Most local supplier should have them in stock for few cents.

As i remind, LM317P shoul be a FP(FullPack) casing. No need for insulator. Is it still available??? i don't know, go... search

[eoasap]

maybe try a small fan to promote forced-convection heat transfer ?

[docwisdom]

I will give the insulator angle a shot.
Steve, thanks for the info on the fullpack. Have you ever heard of a larger amperage unit available in fullpack. I couldnt find a LM350 version specifically.

Any DIP varieties that someone would recommend? I am running DIP mosfets and I am liking them so far.

I would love to run a fan, but I am trying to make things weather resistant.

cheers

-brian

[mister_e]

There's still another way before jumping to another regulator. The solution is to use a transistor to boost the current. In this case, you can use a TO-92 as regulator and almost any TO-220 in Full-Pack (or isotab someting like that). About the efficiency? fair to bad depending the transistor you'll use. Some have a huge drop between Collector and Emitter when the current rise across.

OR you can even build your own regulator with a simple transistor, zener diode and a resistor. Problem is almost the same as previous

Build one with a PIC or an OP-AMP to monitor the output and apply according correction is a better solution. That's what i did on some occasion.

BUT the ultimate, look at LT1085 but the TAB is often the output so... it solve a problem but not the other. www.linear.com

About a DIP solution? Yish, i can't recommend any if it exist anyways. I feel they'll mostely burn your PCB before.

In many case, you can place a heatsink on your Regulator and secure it on your PCB. This work really well in many case. This avoid the insulator stuff.

As you want to make it 'water-proof' Less holes, and screw have to be consider... except if you really want to add some scellant.