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

  • From: Hirshtal Itzhak <ihirshtal@xxxxxxxxxx>
  • To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
  • 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
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