Sink0
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Right. In 4-layer board you can made power and ground layers. This is very good for power integrity. Good power means stability also in high frequency operations. Also having gnd plane is better for impedance control because manufacturers need a reference plane to do impedance measurements in production.when should i consider using a 4 layer board and not a dual layer one? I belive this is pretty much related to the maximum frequency and impedance control right?
I think that such structures are recommended because they implement two ground references for signals.Can any one help me understand the good and bad points of each possible stack up possibility?
Place all of your powers on one pwr layer to keep ground undisturbed. If you plan to place more parts on top then choose TOP-VCC-GND-BOTTOM. That is because you can't route good in top: components are on top. Route your signals mainly on bottom. Then you have good reference for bottom's impedance control and full empty layer without parts installed. In addition you will have power layer closer to components. Route ceramic caps in way PART_PIN-CAP_PIN-POWER_VIA. If you choose TOP-VCC-GND-BOTOM stackup then your power vias will connect to power layer through a smaller connect as you choose TOP-GND-PWR-BOT. You get then lower inductance in current path and higher capacitor performance in power filtering. And this is a key to good high spped design. Finally fill all empty space with GND.So should i go for: TOP - GND - VCC - BOTTON
or TOP - VCC - GND - BOTTON
Again, as i said above, if you place parts including caps on top you get the best result including routing space. Placing caps on bottom is needed only in case of BGAs, where you can't connect a power pin with directly to cap pin. Such placement lead to greather inductance in current path. Here is two cases.I could place my capactiors on top layer, and route most of my signals on botton layer.. which one is more recommended?
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is there any know workaround to avoid this problem?
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