[SI-LIST] Re: Sj frequency and relation to BER

  • From: vinod ah <ah.vinod@xxxxxxxxx>
  • To: Istvan Novak <istvan.novak@xxxxxxxxxxx>
  • Date: Mon, 17 Jun 2013 17:34:41 +0530

hi,

Can you please help me out to understand the relation between bit time
of 200ps and 33MHz Sj. I understand that 40ps of Sj is integer
multiple of 200ps bit time, but what i observe is even with 40ps Sj
@10MHz or 40ps Sj @50MHz, no BER issue.

BER fails only for 40ps Sj @33MHz.

Regards
Vinod A H

On Mon, Jun 17, 2013 at 5:27 PM, Istvan Novak <istvan.novak@xxxxxxxxxxx> wrote:
> Vinod,
>
> Your nominal bit time and deviation of sinusoid jitter is in perfect integer
> relationship, which could make it statistically very sensitive to small
> variations of parameters.
> I just wonder how your circuit would behave if you detuned one or the other
> slightly but noticeably.
>
> Regards,
>
> Istvan Novak
> Oracle
>
>
>
>
>
> On 6/17/2013 5:31 AM, vinod ah wrote:
>>
>> Hi all,
>>
>> I am testing a serial IO Rx running at 5Gbps to meet BER of 1 in
>> 10^-12. I am using BERT for testing where i sweep the Sinusoidal
>> jitter (Sj) from 10 MHz to 50 MHz with Sj amplitude being constant
>> 40ps.
>>
>> I see BER failure at 33MHz, while there is no BER failures at any
>> other Sj frequencies. The CDR in Rx  is having JTF of 3.5MHz, hence it
>> won't track the jitter of 10MHz to 50MHz.
>>
>> So was trying to find what might be causing the BER failure at 33MHz,
>> while the BER passes at 50MHz or 10MHz. Unable to understand relation
>> of Sj frequency to BER.
>>
>> Regards
>> Vinod A H
>>
>>
>
>
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