trackwidth power-lines LM4780

[rho]

I'm trying to design a PCB for an LM4780 chip-amp. It will be used in inverted mode (stereo). Powersupply wil be about +/-30V. Speakers are 8 ohm.
What would be the minimum width of the tracks for the positive, negative and ground rails?
The amp will be used in a small room (10m²), and I don't play all that loud. Still I like a little "build-quality" in my design.

[costiss]

the larger it is possible. when poppulating the board, bend the pins to touch on the copper and then solder them, and screw the cables on the board. this way you can eliminate resistances to a minimum.. your tracks @ 8R will carry ~3Apeak.. thats not really very low (pcb).. if its possible, manufacture the boards on 0.75 mm copper.. it will make a difference..

[rho]

I will have to contact my manufacturer for the thicker copper. As far as I know it isn't possible.

It's a dual layer pcb, so the pins will need to go trough the holes.

[costiss]

the pins will go through the holes and then be bended to touch the copper surface.. use rather large pads to be able to screw the cable on them.. i dont see why you pcb man. couldnt make 0.75/1 mm copper.. mine does..

[rho]

Maybe he can. I just haven't found the option on the order form yet.

I'll send him a mail to get some info on that.

Where do you get your pcb's from?

[Mr Evil]

If you can't make your tracks thick or wide enough, then consider running a second parallel track on the other side of the board, if your layout allows for it. Not only will it increase the current capacity but it also halves inductance (which thicker tracks do not).

[rho]

There is no room on the other side.
I think I managed to get the positive and negative power-lines wide enough. Only GND isn't what it should be in my opinion.
At the smalles point it's just 2,5mm or 100mil wide.

[jackinnj]

A trick which I use is to set the trace width on a net to something like 20 mils at the outset, connect all the nets, then reset the trace widths for the ground, power and output traces to 40, 60 and 100 mils (that is, increase each of these to 40 mils, then 60, etc.) -- each time you widen the trace you will find areas where the errors show up and you have to manually reset the trace width around pins or move from adjacencies.

[rho]

I worked that way.

The problem area is between the 2 rows of pins of the LM4780.

The ground is routed in star so maybe it isn't that big of a problem. Ground from the speakerterminals has its own track (width = 275mil) for each channel.

[jackinnj]

go to http://www.national.com/appinfo/audi...19,968,00.html
you can download the Gerber Files AND the Layers in two zip files. For convenience, I downloaded the composite layer file, put it on my website, and post it below. THis should give you a good idea of how to do it under any configuration:
http://www.tech-diy.com/Chipamps/LM4...site_Final.gif