[SI-LIST] Re: crosstalk
- From: "Lakshmi Narayanan Sowrirajan, ERS-HCLTech" <lakshminarayanans@xxxxxxx>
- To: Massoud Shakeri <massoud@xxxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Tue, 9 Aug 2011 12:32:14 +0530
Hi Brian,
1) What is your single ended line trace width?, assume it is 5 mils for
now.
2) What is your Diff line width and spacing?, assume it is 4x4 for now.
(4 mil width and 4mil spacing to achieve 90/100 ohms)
With the above numbers the SDA line is spaced 5x apart from the SERDES
considering the 4mil spacing in the DIFF pair, if you consider the single ended
line width for spacing analysis you are 4x away from the DIFF SERDES.
I don't think we can do spacing more than 4x/5x practically in any
boards. So you should be good to go.
Most of the SERDES lanes the design requirement is only 3x from other
high speed signals with steep rise time to minimize crosstalk.
Thanks & Regards
Lakshminarayanan. S
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Massoud Shakeri
Sent: Tuesday, August 09, 2011 11:38 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: crosstalk
Brian,
If the length of these two tracks is 1 or 2 inches at 20mils distance,
usually it should not be a problem, because SDA is around 1 Mbps and orders
of magnitude less than SERDES. But there are some issues that you need to
consider:
- Say you have 300 mV budget for crosstalk on SERDES, and crosstalks from
other lines are already close to the budget, so passing SDA line close to
SERDES may cause crosstalk to surpass the budget, and you need to change
something to bring it lower.
- Crosstalk from SERDES on SDA usually cannot make SDA to malfunction. But
more important issue is SDA line can be a good antenna for 10GB/s signal if
it's on top or bottom layer, and you may have more trouble with EMI/EMC.
- For an exact answer you need to do a post-routing simulation, for
example with Hyperlynx. It does not take much time to do that. You can
perform simulation on a few nets including SERDES and status lines close to
them.
Massoud Shakeri
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of tianluchuan2005
Sent: Monday, August 08, 2011 6:12 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] crosstalk
I have a question need your help.
There is a via, the net is SDA of I2C, is close to 10Gb/s SERDES, the
distance is about only 20mils.
And I am afraid if there is the crosstalk between the SDA and SERDES.
I don't know if the distance is safe, or the SDA have no influence to SERDES
?
Thanks !
-Brian Tian
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