[SI-LIST] Re: Multiple power planes coupling to ground

I was just wondering if the plane stack 

 VCC1
 |
 GND
 |
 VCC2
 |
 GND
 |
 VCC3

could be a better alternative. But we can not be sure unless we know what 
signals are above and below these power layers.

Vikas Shukla

http://referencedesigner.com




--- On Mon, 9/22/08, Joseph Pankow <jhpankow@xxxxxxxxx> wrote:

> From: Joseph Pankow <jhpankow@xxxxxxxxx>
> Subject: [SI-LIST] Multiple power planes coupling to ground
> To: si-list@xxxxxxxxxxxxx
> Date: Monday, September 22, 2008, 12:40 AM
> Hello all,
> If you have multiple power planes sandwiched between 2
> ground planes -
> somewhere in your stackup - next to each other like so:
> 
> |
> GND
> |
> VCC1
> |
> VCC2
> |
> VCC3
> |
> GND
> |
> 
> From a high-frequency noise filtering/decoupling
> standpoint, VCC1 and VCC3
> have relatively good capacitive coupling to ground, but
> what about VCC2?
> 
> I understand that there will be capacitive coupling between
> VCC2 and the
> other planes, but does this still give me a reasonably good
> filtering scheme
> for VCC2 at high frequency? Or does it just couple VCC2
> noise onto my other
> power planes?
> 
> I'm trying to visualize the loop currents to ground
> when devices draw power
> from VCC2. Will the VCC2 power noise will couple directly
> through the other
> power planes to ground, or will the other power planes will
> act like shields
> so that VCC2 no longer has good low-inductance filtering
> for high frequency
> noise?
> 
> Any insight would be appreciated.
> 
> Thanks,
> Joseph
> 
> 
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