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PCB stackup advice

sgufa , 07-05-2016, 04:24 AM
Hi all, i need some suggestions for 6 layer stackup. I have some high speed 90 and 100 ohm dfferential pairs + 2 different Voltage sources (one 3.3V and one 5V). Could you suggest how to distribute on the layers?

i've done this way following the example here ( http://www.fedevel.com/welldoneblog/...4-6-Layers.pdf ) but i need advice:

layer1 : mixed signals
layer2: gnd
layer3: High speed signals
layer4: 3V3
layer5: 5V
layer6: mixed signals

Any help would be much appreciated. Thank you
mairomaster , 07-05-2016, 05:43 AM
It seems good to me, but you might be able to optimise it even more. It all depends how busy is on the board.

For example if it's not that complex in terms of power distribution, you might be able to get the 3V3 and 5V on a single layer and use one more ground plane (Layer 5). That could help the Layer 6 mixed signals. However, if you don't have sensitive signals on Layer 6 there is not much point doing that. On the other hand, if Layer 3 signals are really high speed and sensitive, it will be good to have a solid power/GND plane on L2 and L4 (the way it is now).

Can you please give a bit more information about what chips you are using, what interfaces, etc.
sgufa , 07-05-2016, 05:54 AM
ethenet, pci-express, usb3.
robertferanec , 07-05-2016, 07:36 PM
I agree with @mairomaster.

@sgufa also, you can have a look how we did it on the iMX6 Rex baseboard: http://www.imx6rex.com/application/i...lopment-board/ Maybe that can help you too.
sgufa , 07-08-2016, 03:43 AM
@robertferanec you mean L2 L5 gnd and L4 power (3v3 and 5V on the same layer)?
robertferanec , 07-08-2016, 07:23 PM
For example, yes, you can use the same stackup and layers - it's same as suggested by @mairomaster. It really depends on your board.
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