RE: [IBIS-Users] c_comp calculation

Shivani,

You can calculate the lowest frequency of your channel by using
the maximum run length of 1-s and 0-s of the PRBS pattern and
the maximum frequency by using the 1010 pattern.  Multiply the
max frequency by 3 to include the 3rd harmonic to get a better
edge rates.  This will give you the frequency range of interest
for the channel.

Try to find a C_comp value in this frequency range.

I hope this helps,

Arpad
=================================================================

From: Shivani Sharma [mailto:shivanis1406@gmail.com]
Sent: Tuesday, November 11, 2014 10:55 PM
To: Muranyi, Arpad
Cc: ibis-users@eda.org
Subject: Re: [IBIS-Users] c_comp calculation

thanks Arpad

If buffer input signal is PRBS-7, 2.5Gbps, there would be many frequency components in the signal. So what should most likely operating frequency be in this case?

Regards
Shivani

On Tue, Nov 11, 2014 at 9:12 PM, Muranyi, Arpad <Arpad_Muranyi@mentor.com<mailto:Arpad_Muranyi@mentor.com>> wrote:
Shivani,

#1)  The V-t data in IBIS models includes the C_comp effects, this
is why C_comp shouldn’t be visible from the inside, because that
means that the V-t data is not loaded by C_comp to slow it down.
An IBIS simulator should reproduce the V-t data if you load the
buffer with the same V_fixtre and R_fixture load with which the
V-t data was generated, no matter what C_comp value you have.

#2)  You should use the frequency for obtaining C_comp which is
most representative of the buffer’s signal frequency.

I hope this helps,

Arpad
=====================================================================

From: owner-ibis-users@eda.org<mailto:owner-ibis-users@eda.org> [mailto:owner-ibis-users@eda.org<mailto:owner-ibis-users@eda.org>] On Behalf Of Shivani Sharma
Sent: Tuesday, November 11, 2014 4:57 AM
To: ibis-users@eda.org<mailto:ibis-users@eda.org>
Subject: [IBIS-Users] c_comp calculation

Hi all

I have a few queries-

1. C-comp is invisible looking from inside but visible looking from outside of Tx driver model.  In IBIS, does V-t include c_comp effects?. During spectre sims, changing pad capacitance does change V-t data.

2. To calculate c_comp, how is most likely operating frequency of buffer decided.


thanks
Shivani

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