Vcc and GND in multilayer PCB?

[mitaka]

vcc layer

Is there a meaning wich plane is above - VCC or gnd in multilayer PCB?

 

[flatulent]

multilayer pcb ground

You are better of having the higher speed signal traces next to the ground plane and then if necessary, the lower speed ones next to the Vcc.

 

[tom_hanks]

multilayer pcb gnd

Is there a meaning wich plane is above - VCC or gnd in multilayer PCB?

If layers are not fixed properlly then chances of crosstalk n noise in signals get increased...so the places of plane play imp role...

VCC layer should always be put away from top layer.
GND layer should be more as compare to VCC layer...

 

[Beetroots]

routing gnd on a pcb

Put the Power and ground layers adjacent to each other.

 

[hienpv]

vcc pcb

there must be a low impedance path between power and ground

 

[hienpv]

layer vcc pcb

at high speed, keep ground and power planes directly adjacent

 

[hienpv]

multilayer pcb ground plane

use extra ground planes, not power planes, to isolate routing layer

 

[leo_zhu]

connecting ground planes in multilayer pcbs

Hi flatulent,
I can't understand you. Some TTL signal and CMOS signal's return path is VCC, some of them are high speed signal. But I think they should be route next the VCC plane for a good return path. Do you think so?

 

[TurboPC]

pcb vcc layer

use extra ground planes, not power planes, to isolate routing layer

Interesting! I did not know abot this one. I used to isolate routing planes with ground planes OR power planes. I will change my ways and avoid isolate wiht power plane in the future.

Can someone explain me why it is better to place power and ground planes as close as possible for high speed design? How fast is "high speed"?

Thanks!

 

[hienpv]

gnd plane coupling vcc plane

u should routing your high speed trace between to grounds plane!

 

[TurboPC]

pcb vcc plane

Assuming you have an 8 layer board. Sometimes adding a second ground plane may mean having to go to a 10 layer board. What would you do? Use only 1 ground plane and hope it will work or go right ahead to 10 layers?

 

[leo_zhu]

pcb layout vcc

"Place the power and ground plane close", I think it means place the power layer next ground layer in mulitlayer PCB for a good coupling. Reduce the noise of power layer and ground layer.

 

[leo_zhu]

signal ground plan multilayer

if the signal rise time less than 6*signal dealy time. we call it high speed signal.

 

[hienpv]

vcc ground multi layer pcb

yes! some one use 6, and some one use 8*signal delay time

 

[leo_zhu]

multilayer pcb power ground plane

for 8 layer high speed board, i have a good case
top-ground-signal-power-ground-signal-ground-bottom
if you think it is not enough signal layer you should use 10 layer board.

 

[hienpv]

vcc layer meaning

i think, this stack up is google for clock plane (you should routing all clock signal in a plane)

-------------------GND
-------------------clock layer
-------------------GND

 

[hienpv]

48 vcc meaning

and in high speed design, this stack up can be use

Layer 1 ---------------------------- Device and signal1
Layer 2 ---------------------------- Power plane
Layer 3 ---------------------------- GND plane
Layer 4 ---------------------------- Signal 2
Layer 5 ---------------------------- GND plane
Layer 6 ---------------------------- Signal 3
Layer 7 ---------------------------- Signal 4
Layer 8 ---------------------------- GND plane
Layer 9 ---------------------------- Signal 5
Layer 10--------------------------- GND plane
Layer 11 ---------------------------- Power plane
Layer 12---------------------------- Devices and signal 6

 

[leo_zhu]

about ground and vcc planes

yes, clock signal , high speed signal and other important signal can route on this layer. we call it "high quality signal layer" ^_^

 

[TurboPC]

vcc in pcb

and in high speed design, this stack up can be use

Layer 1 ---------------------------- Device and signal1
Layer 2 ---------------------------- Power plane
Layer 3 ---------------------------- GND plane
Layer 4 ---------------------------- Signal 2
Layer 5 ---------------------------- GND plane
Layer 6 ---------------------------- Signal 3
Layer 7 ---------------------------- Signal 4
Layer 8 ---------------------------- GND plane
Layer 9 ---------------------------- Signal 5
Layer 10--------------------------- GND plane
Layer 11 ---------------------------- Power plane
Layer 12---------------------------- Devices and signal 6

If you need controlled impedance (like 50-ohm traces) traces on the top layer, the power plane in your layer 2 will have the return current instead of the ground plane. Do you suggest to move the controlled impedance traces to another layer or change the power plane from plane 2 to another one? I prefer my controlled impedance traves on the top layer to avoid vias or discontinuties.

Thanks for the info.

 

[hienpv]

4 vcc gnd clk & high speed clk

i think you should not routing the controlled impedance traces on the top layer. The controlled impedance should be routed on stripline layer!