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Old 18th July 2011, 04:13 PM   #1
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Cool From schematic to board layout - Help & hints needed

Did some attempts to create my own layouts before, it has always been a pain in the a** for me. Today I gave it another try

First I'd just like to know if I built in some (seroius) flaws or if my way of thinking is alright so far. In addition I'd be happy to get some links to some tutorials ASO. I guess there is another fundamental than just trial 'n error ...

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Old 18th July 2011, 05:03 PM   #2
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Just found a flaw myself ... DANG! Corrected Version:

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Old 18th July 2011, 05:23 PM   #3
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When you say a flaw, do you mean an actual electrical error, rather than simply a less-than-elegant component placement etc.? These days I use a schematic capture and layout package that generates a netlist, ensuring that I don't make an electrical error in the placement. In fact, it won't even let me make an erroneous connection when laying out the board. Once complete I can run a Design Rule Check (DRC) and check for errors such as tracks too close together etc.

The one I use is Kicad - it's free.
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Old 18th July 2011, 05:32 PM   #4
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Quote:
When you say a flaw, do you mean an actual electrical error, rather than simply a less-than-elegant component placement etc.?
Indeed I meant errors, thanks for clearing things up. I've just downloaded KiCAD, will try it tonight.
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Old 18th July 2011, 05:35 PM   #5
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Assuming it is correct electrically, your layout looks fine to me, with everything placed around a low impedance ground. But in a circuit like this, I wonder if there would be any reason not to flood fill everything with ground to make it even lower impedance? (Easy to do with packages like Kicad).

Being the cautious type, I might swap U1 around so that I could, if necessary, bend the chip down and bolt it down for heatsinking purposes if I later found it necessary.

Don't forget your PCB mounting holes.
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Old 18th July 2011, 05:36 PM   #6
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Quote:
Originally Posted by Groundloops View Post
Indeed I meant errors, thanks for clearing things up. I've just downloaded KiCAD, will try it tonight.
Good luck!
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Old 18th July 2011, 07:57 PM   #7
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I asume that red is your silkscreen layer. I would put all the parts numbers (yellow) on the silkscreen layer in such a way that when the components are in place the part# is still visible. Add polarity info to the electrolytics. Your R4, 5, 7 13 and 14 seem to be "standing up" you have enough space on your board to lay them down. Good board for a first try! E
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Old 19th July 2011, 12:56 PM   #8
marce is offline marce  United Kingdom
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An eclectic mix of PCB related links.
Under the Misc section there are some links for initial PCB design tutorials etc.
Have plent more documentation once you get through this lot
Attached Files
File Type: txt PDS_and_Capacitors_Links.txt (3.2 KB, 46 views)
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Old 22nd July 2011, 11:17 AM   #9
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Hi everyone. This seems like just the thread for me, as I was going to come and ask advice in getting every bit of sonic performance out of my boards.

I've laid out this PCM2706-based really simple USB DAC and I'd like your opinion on the board. Does it look ok? The bottom side is all continuous copper. I have little experience in dealing with analog signals on PCB since I'm a more digital guy. It would be especially interesting to hear about what kind of capacitors to use or not to use, where to put them and so on. I don't want to lose any sonic performance because of bad PCB design.

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I don't have a schematic to post right now but will post that later today.
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Old 22nd July 2011, 11:33 AM   #10
marce is offline marce  United Kingdom
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Firstly, the PQFN requires more vias down to ground, preferably 1 per ground pin.
Whare are the power tracks!
This is digital mainly, each ground pin should be viaed down to the ground plane, not routed to star points.
Move the capacitrs on the crystal to the otherside of the crystal and minimise the track length.
Put a ground guard ring around the crystal signals.
Turn C22 around.
where are the decoupling capacitors!

In post #8 I put a text document with some basic PCB design related links, all are relevent to PCB design.
Some relevant to mixed signal design.

http://www.hottconsultants.com/techt...gnd-plane.html
http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
An intuitive, practical approach to mixed-signal grounding
http://focus.ti.com/lit/an/sbaa052/sbaa052.pdf
http://focus.ti.com/lit/ml/slyp167/slyp167.pdf
http://www.ieee.org.uk/docs/emc1206a.pdf
http://www.icd.com.au/articles/Split...s_AN2010_6.pdf
http://www.analog.com/static/importe...0Grounding.pdf
http://www.analog.com/static/importe...als/MT-031.pdf
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