[SI-LIST] Re: SPLIT POWER PLANE
- From: "avulab" <avula.bhaskara@xxxxxxxxx>
- To: "'sreekanth namboothiri'" <nsreekanth@xxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 6 Jun 2006 16:43:46 +0530
Hi,
I think we can use stitching capacitor concept here for providing return
current path.
The Signal will use the adjacent planes as reference planes regardless of
their potential. What all we have to do is; create a system which allows
continuous current path for all case of buffer switching.
The drivers of your signal traces use a certain voltage for power.
So, if their signal traces induce a return current on one or more reference
planes,
You need that return current to return to the voltage pin of your driver.
Example:
If you are using drivers which operate on 3.3V, and you induce return
currents
On a ground plane, a 3.3V plane, and a 2.5V plane, you need to have a return
Path connection between 3.3V and ground, 2.5V and ground, and 3.3V and 2.5V.
This would mean stitching the two planes with several small caps, and
Placing decoupling caps from 3.3V to ground at both ends of the system, and
Decoupling caps from 2.5V to ground and/or 2.5V to 3.3V.
The 2.5V to 3.3V stitching capacitor should be places as close as possible
to the Signal, where it is crossing the plane.
I would suggest using more than one capacitor to stitch the planes, because
Signals sharing a return current path (a capacitor) will have greater
Crosstalk.
Please correct me if I am wrong
Best Regards
Bhaskara Reddy
"Don't judge each day by the harvest you reap, but by the seeds that you
plant"
_____
From: sreekanth namboothiri [mailto:nsreekanth@xxxxxxxxxxxx]
Sent: Tuesday, June 06, 2006 2:37 PM
To: si-list@xxxxxxxxxxxxx
Cc: avula.bhaskara@xxxxxxxxx
Subject: SPLIT POWER PLANE
Hello Gurus,
I have a power splitt in my design which is unavoidable,and due to some
routing constraints some signals are crossing over the split in another
layer.
Is there any solution for such sistuations?
I rembr , earlier i had almost same issues with GND splits and we managed it
with tying up both the GNDs with 0 ohm resistors.
What can be done ,in the case of power split?
Sreekanth
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