From schematic to board layout - Help & hints needed

Groundloops · 18th July 2011, 04:13 PM

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 ...

Groundloops · 18th July 2011, 05:03 PM

Just found a flaw myself ... DANG! Corrected Version:

CopperTop · 18th July 2011, 05:23 PM

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.

Groundloops · 18th July 2011, 05:32 PM

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.

CopperTop · 18th July 2011, 05:35 PM

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.

CopperTop · 18th July 2011, 05:36 PM

Quote:

Originally Posted by Groundloops

Indeed I meant errors, thanks for clearing things up. I've just downloaded KiCAD, will try it tonight.

Good luck!

mickeymoose · 18th July 2011, 07:57 PM

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

marce · 19th July 2011, 12:56 PM

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

Entropia · 22nd July 2011, 11:17 AM

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.

I don't have a schematic to post right now but will post that later today.

marce · 22nd July 2011, 11:33 AM

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

18th July 2011, 04:13 PM	#1
Groundloops diyAudio Member Join Date: May 2004 Location: Hamburg / Northern Germany	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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18th July 2011, 05:03 PM	#2
Groundloops diyAudio Member Join Date: May 2004 Location: Hamburg / Northern Germany	Just found a flaw myself ... DANG! Corrected Version:

18th July 2011, 05:23 PM	#3
CopperTop diyAudio Member Join Date: Feb 2009 Location: UK	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.

18th July 2011, 05:35 PM	#5
CopperTop diyAudio Member Join Date: Feb 2009 Location: UK	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.

18th July 2011, 07:57 PM	#7
mickeymoose diyAudio Member Join Date: Nov 2008	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

22nd July 2011, 11:17 AM	#9
Entropia diyAudio Member Join Date: Mar 2011 Location: Jyväskylä	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. I don't have a schematic to post right now but will post that later today.

22nd July 2011, 11:33 AM	#10
marce diyAudio Member Join Date: Jun 2007 Location: Blackburn, Lancs	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