[SI-LIST] Re: 2.5Gbps
- From: "Zabinski, Patrick J." <zabinski.patrick@xxxxxxxx>
- To: dorin.oprea@xxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Fri, 18 Jul 2003 08:40:48 -0500
Dorin,
The answer will come down to the target bit error rate your
shooting for with the link. From that, you can determine
the signal to noise ratio, which will lead you to some
specs for the signal strength.
There is literature on the web and in text to get you going,
but I suggest you start with the basics on bit error rate
analysis related to signal to noise ratio. This will give
you a good idea how they relate and how you can eventually
derermine the signal margin you want.
As an example (not necessarily applicable to your situation),
you might determine a bit error rate (BER) of 10^-12 is
sufficient for your link. From that, you can determine a
signal to noise ratio (SNR) of 7:1 is required.
You'll then have to determine or estimate your effective RMS
noise on your link. For typical links, 40-50 mV of RMS noise
is a reasonable guess, which will then determine that you
need a 280-350 mV opening within the eye diagram (note: 280-350
mV opening from threshold to inside portion of eye).
Again, this is an example that is not specifically related to
your application, so you'll want to perform your own analysis.
Also, I highly recommend you read up on the topic of BER
vs SNR, as it will help you with some of the basics and
the not-so-basic issues.
Hope this helps,
Pat
> Hi,
> There is a 2.5Gbps system link through the back plane with an
> interconnect length of 35".
> What should be the simulated voltage level for a receiver with 100mV
> threshold so that one can be confident in his design?
> Is it 200mV (2*100mV) sufficient? What is preferred value?
> How much jitter on the simulated eye is accepted?
>
> Thanks,
> Dorin
>
>
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