Voltage regulation circuit 12V to 5V in 5A range

[tumbleweed]

I just noticed the LM1084-ADJ is claimed to "provide 5 A at high efficiencies and very low drop-out." I just ordered a few from Digikey.

The only difference between the LM1084-ADJ and the fixed output LM1084-5 is the latter already has the resistors to set the output voltage built inside it. You will only get 5A out of it if you have the input > the Vdo drop out voltage spec, and stay within the max power dissipation. With no heatsink you're not going to get anywhere near 5A out, not with 12V in.

You said the output voltage of the LM1084-5 dropped when you added a load. That shouldn't happen as long as you're within the datasheet specs.

If you're trying to get 2.5A out, with your 12V adapter that gives a Pd = (12v-5v) x 2.5 = 17.5W !!

Yeah, I'm waiting for a 9V 2A wall adapter to help reduce the waste heat. I'm getting 7V 2A wall adapter tomorrow to reduce that even more.

You'll need an adapter with more than 2A out if you want 2.5 or 5A out of the linear regulator.