What is the difference between an isolated IC and a non-isolated IC?

[DJ Exprice]

Could I attach both of my non-insulated chips to the case of my amp (its metal). There is no other connection besides the ground touching the case.

[!]

Originally posted by DJ Exprice
Could I attach both of my non-insulated chips to the case of my amp (its metal). There is no other connection besides the ground touching the case.

No, you wouldn't want to do it, because V- is tied to the non-isulated chip tab and it is negative, relative to ground. In other words you'd be shorting out half your power supply.

[DJ Exprice]

Originally posted by !



No, you wouldn't want to do it, because V- is tied to the non-isolated chip tab and it is negative, relative to ground. In other words you'd be shorting out half your power supply.

You mean ground can't touch ground? Im confused The V- is ground, so i don't understand. My transformer will be insulated in it's case inside of the amp that will be screwed to the amp's metal case - no metal connection. The LM3886s will have each other's V- anyway. Do I need to connect the transformer to the amp's metal case via it's ground wire? Can I connect all of those? I will be using a 24v 6.3 amps transformer, just to clarify things.

[!]

Originally posted by DJ Exprice



You mean ground can't touch ground? Im confused The V- is ground, so i don't understand. My transformer will be insulated in it's case inside of the amp that will be screwed to the amp's metal case - no metal connection. The LM3886s will have each other's V- anyway. Do I need to connect the transformer to the amp's metal case via it's ground wire? Can I connect all of those? I will be using a 24v 6.3 amps transformer, just to clarify things.

No, supposing your supply is 24-0-24. The first 24 is V+, 0 is Gnd and 2nd 24 is V-.

V- is not ground in a dual supply. In this case it is 24 volts negative (lower than) the ground.

So you are going to use a single supply instead of dual, since you only mention "24V 6.3A"? It would be helpful if you post clear and complete schematics of exactly what you want to do, a mistake in this can easily damage something.

[sam9]

Unless you are going to push it to the max, I've found no reason not to use the isolated version. Even with pretty skimpy heatsinks I've never got one close to "too hot" (defines as can't touch and leave your finger on it).

[DJ Exprice]

I guess I'll just use some skimpy heatsinks. Im not pushing it to the max. Heatsinks sound the easiest. Thanks for all your help on the transformer and the grounding info!

-Exprice

[DJ Exprice]

Sure (above) thats for my older one. My newer idea for an LM3886 amp is TF with connection to the case (I need to get thermal grease for this one though I figured out that V- is NOT ground and feel like a complete nincompoop for not realizing that earlier. I also know that 0v on the transformer should NOT touch AC Primary ground. I also got some wrong-size q-pads but can still attach thermal grease (when I get some) to part of the chip and most of the pad and probably still get some good transfer of heat . Thanks guys!