[SI-LIST] Transmitter Jitter Setup for simulations of 5Gbps

  • From: "Dmitriev-Zdorov, Vladimir" <vladimir_dmitriev-zdorov@xxxxxxxxxx>
  • To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 20 Jun 2013 15:57:00 +0000

Hi Itzhak,

Let me note that the proper IBIS AMI model should include jitter definitions in 
its ami parameter file, by way of reserved parameters, such as DualDirac, 
Tx_DCD, and possibly Gaussian. This is typically done by model creators.

If the models lack jitter settings, there is a mechanism in HL to specify it on 
your own, and this is seemingly what you do. Generally, your approach seems 
correct, but I would recommend using the Tx_DCD keyword to specify DCD in ami 
file itself instead of adding DCD to UBHPJ . Yes, to do this, you will need to 
edit the ami file or its copy.

The difference between sigma=0.01UI or 0.007UI (0.1/14) could be considerable, 
because Gaussian component is unbounded, and dominates at low probability level.
It's better to operate with numbers. What do you mean by "the eye is completely 
open"? How large is jitter caused by ISI only?

My suggestion is to discuss technical details off-line. 

Vladimir


>From: Hirshtal Itzhak <ihirshtal@xxxxxxxxxx>
>Subject: [SI-LIST] Transmitter Jitter Setup for simulations of 5Gbps SERDES
>Date: Wed, 19 Jun 2013 09:56:33 +0000

>Hello all,
>I have a question relating to the proper use of jitter in hi-speed simulations 
>of several Gbps pairs.

>I've been using HyperLynx IBIS-AMI Channel Analysis tool in order to simulate 
>5Gbps channels going from one PCB to another one through a motherboard.
>I use IBIS-AMI models from the Tx/Rx vendors and S-Parameter models for the 
>connectors involved.

>The main problem for me is understanding how to use the jitter specification 
>for the transmitter.

>The transmitter data sheet defines miscellaneous Near-End (Tx) Template 
>Intervals, part of which are jitter intervals, which include T_UBHPJ 
>(Uncorrelated Bounded High Probability Jitter) of 0.15UIptp, T_DCD (Duty-Cycle 
>Distortion) of 0.05UIptp and T_TJ (Total Jitter) of 0.30UIptp.

>I have been using these parameters as follows inside the simulation tool setup:

>-          Dual Dirac Jitter: 1st  mean = -0.1UI, 2nd mean = +0.1UI 
>(accounting approximately for the sum of the 1st 2 jitter parameters, which 
>equals 0.2UI)
>-          Sigma of Random Jitter = 0.01UI, which results from subtracting 
>the1st 2 parameters from the total jitter (yielding 0.1UI) and dividing the 
>result by 14 (the ratio [for BER of 10**(-12)] between peak-to-peak jitter and 
>Sigma. I rounded the final result up a little to get 0.01UI.

>So, to conclude: Have I used the simulation tool's jitter setup correctly to 
>account for the Tx jitter definitions? Because when I do that, I get a closed 
>eye (relative to the Rx eye-mask spec). Without these jitter elements the eye 
>is completely open!

>Also, what BER ratio should I use for the Sigma definition? Should it be 
>according to the desired BER on the receiver?

>Thanks for your help

>Itzhak Hirshtal
>Elta
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Thank you.

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  • » [SI-LIST] Transmitter Jitter Setup for simulations of 5Gbps - Dmitriev-Zdorov, Vladimir