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besim321123 , 12-05-2019, 04:26 PM

Hi,

I have a question about my 6 layer pcb.

First layer is Top layer
Second layer is GND layer
third layer is Signal layer ( RMII , USB and other signals)
four layer is Signal layer ( SDRAM Data pins , Address pins)
fifth layer is power layer (3v3)
sixth layer is Signal layer (RGB interface for TFT display)

Does This Layer stack affects my SDRAM datas or RMII datas and USB signal? I attached all layer photos.

Your ideas and advice are important for me.

Thanks,

robertferanec , 12-06-2019, 12:59 AM

I would probably do it similar way. Just be careful that the signals on L3 and L4 are not routed in parallel.

besim321123 , 12-06-2019, 07:06 AM

My USB and RMII are high speed signal so do they need 2 reference layer? or 1 layer is enough ?

As i said USB and RMII signal on 3rd layer so my reference layer is just 2nd layer. is it problem ? (4th layer is signal layer for SDRAM data)

besim321123 , 12-08-2019, 11:27 AM

Hi Feranec, I wonder the answer to my question

robertferanec , 12-09-2019, 04:40 AM

For L3, reference plane is L2 and you may need to consider also L5 as reference plane. However L5 may not have big influence as I guess it is far away from L3.

The same, for L4, reference plane may be L2 and also L5.

Lakshmi , 12-12-2019, 06:00 AM

I would suggest for the best practice,
L1 - Signal and Gnd pour remaining space
L2 - GND(ref) Continuous
L3 - Signal and Gnd pour
L4 - POWER and can be signal
L5 - GND(Continuous)
L6- signal and Ground pour
And Don't forget add Gnd via near signal via whenever you change signal routing from L1 to L6 OR L3 to L6.
Have power plane and ref (Gnd) next to each other.

robertferanec , 12-13-2019, 02:16 AM

@Lakshmi I agree, that is the stackup what we also often use in our 6 Layer PCBs.