[Gta04-owner] CPU, Memory [BeagleBoard: Lessons Learned...]

Dr. H. Nikolaus Schaller hns at goldelico.com
Tue Mar 8 21:23:46 CET 2011


Am 08.03.2011 um 21:09 schrieb Glenn Moeller-Holst:

> Might be interesting - lot of know-how and experiences?:
> 
> Epecially page (They "only" use 6 layer PCB?):
> 15, 18, 20...25,

Yes, that is right. They were lucky to use just 6 layers because they
did not connect all BGA balls. And, it appears they have different PCB
production rules.

> 
> Lessons Learned Building the BeagleBoard - long slide show:
> http://jkridner.s3.amazonaws.com/esc/BEAGLE_ESC_4.ppt

That document is our "design bible" since we started designing the
GTA04 board... Without, we would never have started the project.

> Something seems to be wrong in page 29 - signal layers must not be placed between power and ground according to TI? See pdf-page 10 swcu55.pdf.

Good observation! Maybe the BB isn't optimally designed either.
Well, it "works as it is" and it is *not* declared as a reference design...

What also could be is that the layer assignment as on page 29 is not
strictly followed in detail because the power connections of the BGAs
are usually on layer 1 and 2.

For the GTA04A3 we have managed to follow the rule on page 10. Especially
because we have the UMTS module which can draw up to 2A peak current
from 3.6V (~7W). This could create strong magnetic fields with GSM burst
frequency...

BR,
Nikolaus


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