RE: [IBIS-Users] FW: C_comp calculation for high speed IOs

Hi, Ajay,

To echo Randy's comments, I also recommend using AC simulations for C_comp
extraction.

I did a presentation about C_comp at last year IBIS Asian Summit. Here is
the link:

http://www.vhdl.org/pub/ibis/summits/nov09b/wang.pdf

Just for the reference.

Lance Wang

978-764-2298

IO Methodology Inc.

SIMDET V2.0 - The best tool for IBIS modeling intergrated with HSpice,
Spectre and Eldo simulators.

www.iometh.com <http://www.iometh.com/>

  _____

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of rrwolff@micron.com
Sent: Wednesday, March 10, 2010 11:19 AM
To: ibis-users@eda.org
Cc: akap.31@gmail.com
Subject: RE: [IBIS-Users] FW: C_comp calculation for high speed IOs

Ajay,

I prefer to use an AC simulation to look at C_comp. You can sweep various
DC bias points and frequencies if you want to make a 3D plot of C_comp
versus DC bias and frequency. The HSPICE syntax is below for this method,
where pad is the I/O node of the buffer. I suggest VDDQ/2 as the bias point
of most interest, and you can decide which frequency to use, maybe one close
to the maximum clock frequency. You just need to ensure that ODT is enabled
to the right value for the DC operating point (so if you need a clock signal
in the model to toggle before ODT turns on, you'll be in trouble and will
need to use .IC statements to ensure control lines are at the right state).

.AC lin 2 400MEG 667MEG sweep dcsweep 0.7125 0.7875 .0375

.measure ac incap find par('-1*ii(Vpad)/(hertz* 2 * 3.1415926)')
at=667000000hertz

Vpad pad 0 DC dcsweep AC 1

Regards,

Randy

Randy Wolff
SI Modeling Manager
Signal Integrity R&D Group
Micron Technology, Inc.
208-363-1764

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of Mirmak, Michael
Sent: Wednesday, March 10, 2010 2:17 AM
To: ibis-users@eda.org
Cc: akap.31@gmail.com
Subject: [IBIS-Users] FW: C_comp calculation for high speed IOs

Forwarded on behalf of Ajay Kapoor.

From: ajay kapoor [mailto:akap.31@gmail.com]
Sent: Wednesday, March 10, 2010 4:34 PM
To: Mirmak, Michael
Subject: C_comp calculation for high speed IOs

[.]

I needed help on follwoing:
I am developing IBIS models for DDR3 IO with following condition that On Die
Termination is turned ON and DDR3 is recieving data.
Can you please suggest a method / setup to calculate accurate Ccomp value
for this model ?
 
Thanks in Advance
AK

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