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PCM2702 USB DAC Revision B - Page 7

post #91 of 670
10/13/05 at 4:38pm
A little detail. On my board, I didn't use thermals (the little cross making it easier to solder to the groundplane) on the smd pads. It allows Eagle to route continuously in some places, where it wouldn't be able to do so with thermals on. And so some critical mils are gained.

Speaking of mils, what are you guys using for a grid ? I'm usually working with a grid of 12.5mil.
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post #92 of 670
10/13/05 at 5:22pm
Thread Starter 
Quote:
Originally Posted by 00940
A little detail. On my board, I didn't use thermals (the little cross making it easier to solder to the groundplane) on the smd pads. It allows Eagle to route continuously in some places, where it wouldn't be able to do so with thermals on. And so some critical mils are gained.

Speaking of mils, what are you guys using for a grid ? I'm usually working with a grid of 12.5mil.
00940:

The grid 12.5mil and thermals are turned off. I use the brd file Guzzler sent me which I presume he got from you. So I should have all your original settings.

Speaking of Eagle, I have a few particular problems with this beast:
* Why do I have to press F2 all the time? Can Eagle redraw automatically?
* If I place a via under an SMD pad as in your picture above, I get a clearance error.
* Can I make SMD ground pads to merge to ground plane without these annoying corner cut-outs?
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post #93 of 670
10/13/05 at 7:48pm
Eagle doesnt automatically redraw that I know of, quite annoying to me too. To place a via under a pad, and not get DRC errors, go into DRC, clearance tab, and change the same signal values to 0mil.
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post #94 of 670
10/14/05 at 3:28am
Quote:
Originally Posted by Alf
Speaking of Eagle, I have a few particular problems with this beast:
* Can I make SMD ground pads to merge to ground plane without these annoying corner cut-outs?
Those cut outs are the thermals Yes, go to "change", "thermals", "off" and then click on your groundplane.
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post #95 of 670
10/14/05 at 7:33pm
Thread Starter 
00940, cetoole: Thanks for the Eagle lesson!

One more question. How can I put a picture on a board?
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post #96 of 670
10/14/05 at 7:35pm
Thread Starter 
Here is an updated board layout following your suggestions.

Board v5 - Top

Board v5 – Bottom

Board v5 – All without bPlace


Feel free to bash it!
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post #97 of 670
10/14/05 at 7:46pm
Thread Starter 
Quote:
Originally Posted by Clutz
Can't you use a larger PCB to address some of these problems? (I don't know anything about PCB layout- I'm just asking out of curiousity)
No, this would not help. If you follow this thread from the beginning you will see that we fight for having the bypass capacitors as close to the IC as possible. The size of the IC and the unfortunate location of its pins makes this a challenge.
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post #98 of 670
10/14/05 at 8:01pm
Looks great!

Is it possible to have shorter leg spacings for C6, C7, C10, and C14? Looks like in order to fit the right cap sizes the spacings need to be a bit shorter. I think those spacings are meant for machine-assembly types with pre-bent legs?

Or I could be totally wrong, but it would be nice if all straight-legged electrolytics that most DIYers use could just slide in without much effort.
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post #99 of 670
10/15/05 at 5:48am
It looks most good.

One could probably spend from now until the end of eternity fiddling with the exact layout, getting the last bit of tightness. But it is well on track.

Might be worth sticking holes at a few separations for the output capacitors, so that those with boutique tastes can indulge them.
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post #100 of 670
10/15/05 at 8:27am
Quote:
Originally Posted by Francis_Vaughan
It looks most good.

Might be worth sticking holes at a few separations for the output capacitors, so that those with boutique tastes can indulge them.
Absolutely right!!
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post #101 of 670
10/15/05 at 8:27am

board space!

If we put this board next to a mint, are they the same size?
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post #102 of 670
10/15/05 at 8:29am
I still recommend using the USB socket with the grounded tabs, makes the whole thing a lot more stable and could improve the shielding. You can just use change->package to do it. It's in CUSTOM.LBR that I sent you. Other than that, looks very nice :
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post #103 of 670
10/15/05 at 9:33am
Quote:
Originally Posted by MASantos
If we put this board next to a mint, are they the same size?
I belive this board is a bit larger than a mint board so I will fit straight into the smallest hammond case (1455C801)


/U.
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post #104 of 670
10/15/05 at 9:56am
Thread Starter 
Quote:
Originally Posted by Francis_Vaughan
It looks most good.
Wow! I thought I would never hear these words.


Quote:
Originally Posted by guzzler
I still recommend using the USB socket with the grounded tabs, makes the whole thing a lot more stable and could improve the shielding. You can just use change->package to do it. It's in CUSTOM.LBR that I sent you.
I do use USB socket from CUSTOM.LBR


[QUOTE=doobooloo]Is it possible to have shorter leg spacings for C6, C7, C10, and C14? Looks like in order to fit the right cap sizes the spacings need to be a bit shorter. I think those spacings are meant for machine-assembly types with pre-bent legs?

Quote:
Originally Posted by Francis_Vaughan
Might be worth sticking holes at a few separations for the output capacitors, so that those with boutique tastes can indulge them
I will publish my notes on the component list soon. Then we can decide what sizes/packages/etc are most suited for this design while remain easy to get and solder. I will tweak the board further to accommodate these parts.
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post #105 of 670
10/15/05 at 11:45am
Ok, cool. Connect the two pads to ground and the plane will fill around them
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