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Subject: Measures taken when signal crosses splits
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eswar
Posts: 0
Online: User is Offline
9/19/2007 10:13 PM  
Hi everyone,

I would be greatful if anyone answer my query.

If a situation occurs where I need to cross the splits what r the measures that needs to be taken and why ? Also If a signal is crossing two splits that of power and GND what are the measures that needs to be taken.

Thanks in advance.

Eswar
Hpattie
Posts: 33
Online: User is Offline
9/21/2007 2:09 PM  
The simple answer is don't cross the split in the plane. If this is not possible, reduce your current loop to the absolute minimum. It is difficult to give a solution without knowing a lot more about your design. A bypass capacitor between the two planes at the point where you are crossing the split will help. Guardbanding is another way to maintain a small current loop.
Regards,
hpattie@entrisphere.com
Harold Pattie C. I. D.+
eswar
Posts: 0
Online: User is Offline
9/23/2007 10:01 PM  
Thanks for you suggestion. But what will be the value of decap and why
Kalevi2
Moderator
Posts: 69
Online: User is Offline
9/24/2007 3:48 AM  
The problem with crossing a split plane is that the return current cannot cross the split so it takes some longer path which adds inductance to your signal (i.e. slows it down) and the convoluted return path usually results in excess emissions (EMI). The faster your edge rate, the more you need to worry. I2C is OK, 800MHz DDR2 is not. Crossing a split plane will probably kill your DDR2 signal, especially if both reference planes are split.
Kai Keskinen
kishore
Posts: 41
Online: User is Offline
9/24/2007 4:10 AM  
There are quite a good number of articles written on this topic, that you can find on the net. One good source to start with is Eric Bogatin's site at:
www.bogatinenterprises.com

Best regards,
Kishore
eswar
Posts: 0
Online: User is Offline
9/24/2007 4:16 AM  
Thanks for the reply
cadpro2k
Posts: 0
Online: User is Offline
9/25/2007 8:39 PM  
Another GREAT site is www.speedingedge.com (Lee Ritchey). You can also get Lee's book "Right the 1st time" online. GREAT book! Highly recommend.

You can check also, www.ultracad.com for SPLITS; and PCD&M magazine online, and search for "split". Lee had an article in it ~2000.

Always get the facts. Nothing is ALWAYS right.

Good day.
MItch
cadpro2k
Posts: 0
Online: User is Offline
9/25/2007 8:45 PM  
Also just did a search on Yahoo (PCB plane splits) and ran across this article. Very informational.

Try it:
http://pcdandm.com/cms/content/view/3413/95/
eswar
Posts: 0
Online: User is Offline
9/25/2007 9:27 PM  
Thanks guys it will check them out.
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Forums > Silicon-package-board > PCB Design > Measures taken when signal crosses splits


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