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Old 9th February 2006, 12:19 AM   #1
gmikol is offline gmikol  United States
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Default Best practices for board layout???

Having gotten bit by the DIY bug, and with plans to build active 2-way and 3-way systems, I downloaded a copy of Eagle and got started.

I quickly discovered, though, that I don't know a #!%!#% thing about audio PCB layout. Need a 600MHz embedded SRAM? I can help. Lay out an active crossover?? No clue. In my world, everything is drawn pretty much as close to minimum as possible, and parasitic coupling to the power supplies is generally a good thing. Inductance is a non-issue.

So...does anybody out there have some good links or tips you can post re: good layout practices for this sort of stuff? You'll have my deepest appreciation...

--Greg
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Old 9th February 2006, 12:44 AM   #2
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try to search on"PCB layout technics".
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Old 9th February 2006, 04:13 AM   #3
gmikol is offline gmikol  United States
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I thought I'd try an example. Here's a battery-powered balance mic pre with phantom power. Schematic and layout. Feedback on the design itself and the layout are both appreciated.

--Greg
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Old 9th February 2006, 04:14 AM   #4
gmikol is offline gmikol  United States
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Default ...and the board

The board...it's 2.75in x 1.5in

--Greg
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Old 9th February 2006, 09:34 AM   #5
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Hi Greg

A couple of points for your delectation. Just the way I would do things though, everyone has their own way of laying out a circuit on a PCB.

Firstly, power. Currently, your power rails are all over the board. I would move the PSU section to the right hand side of the board, then just run two parallel rails right under the ICs. Keep them close, to reduce radiated noise, and as short as possible. It wouldn't hurt to add a 100nF film decoupling cap as close as you can get it to each IC's power pins.

Secondly, layout. Quite often, I play with the schematic for a while, getting things as neat as possible, then try and emulate this on the PCB, so the parts layout on the PCB roughly follows the schematic. Try to keep logical blocks of the circuit together, rather than scattering them all over the PCB wherever they fit.

Hope that helps!
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Old 10th February 2006, 12:46 AM   #6
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I agree completely with Pinkmouse. I'd just mention that the ground plane is a good idea; and there are no isolated islands. And having in and outputs separated at opposite ends of the board as you have is good practice too.

But mostly I wrote this so I could try the nod smiley.
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Old 10th February 2006, 05:56 PM   #7
gmikol is offline gmikol  United States
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I started playing around with PM's suggestion last night. Don't have anything done yet, but it seems to force the layout into a long, skinny shape. I'm trying to jam it onto a small panel along with other stuff that's going to Olimex. So I'm kinda size constrained. I'll post back when I've fixed the layout.

But I guess the bigger question is...for a battery-powered application, is my original layout really that bad? I mean, "raidiated noise" from the PS tracks should be virtually non-existent in a battery supply, no?

Thanks for the input--

Greg
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