[Gta04-owner] CPU, Memory

Dr. H. Nikolaus Schaller hns at goldelico.com
Tue Mar 8 21:15:19 CET 2011


Hi Glenn,

Am 08.03.2011 um 20:32 schrieb Glenn Moeller-Holst:

> Hi Nikolaus
> 
> TPS65950 - oh my - what a chip - to many connections...

Yes... We have to connect approx. 90% of the pads since
we did not connect the keyboard controller.

> Why not let the CPU and memory ride on top of TPS65950?

Because the pin assignment does not fit. And, we just have 2mm space
between the PCB and the battery.

> 
> I looked at pdf-page 12, 13, 33 and 66 - they have "thrown" a lot of functionalty into that chip:
> 
> TPS65950 Data Manual (Rev. E):
> http://www.ti.com/lit/gpn/tps65950
> 
> -
> 
> You have of cause looked at page 12...14 and 23 - and especially 8...9 (wire between vias)? - could you ask them of a reference/example PCB design? They ought to be eager to help costumers?:
> 
> TPS65950 Layout Guide (Rev. A):
> http://www.ti.com/litv/pdf/swcu055a

That is the document we had neglected for the GTA04A2 board.
And the result was that the power supply is not stable.

Now we want to do it better and have worked in their
recommendations and are just fiddling with the remaining
wires that have no special rules.

Yes, Figure 4 shows a potential solution but our PCB
manufacturer can not produce it. Well, they can if we insist
on 60um trace width and clearance, but the price of the PCB
would double.

So we try to stay with the 100um trace width and clearance of the
GTA04A2 board (which had achieved 100% routing). So we know that
it can be done without changing the design rules. It is just a dull and
tedious process...

In the past days we have made progress by fixing some bugs in a
helper tool. So please just be patient... The target can already be
seen at the horizon.

Best regards and thanks for the suggestions,
Nikolaus

PS: looking at the BB Gerbers doesn't really help since they have
some different connections (and placement of connectors and connected
components) and a different manufacturing process. And even if
we would copy 95% it is not sure that we could connect the 5% without
violating design rules.


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