RE: [IBIS-Users] C_comp values

Many vendors will use the same I/O cell for an Input buffer as an I/O
buffer. The parasitics will be about the same for both. Sometimes the
designer will select different cells for input and outputs and you should
see differences in C_comp. Many vendors will just specify the maximum
capacitance at the pin, which will include the package C, so you have to be
careful. Also, many vendors will just publish a max number and then they
will not have to reject anything that comes out of the oven.

We are seeing C_comp values as low as 400fF. Most values on modern
processes run 2 to 3 pF. Older processes could be as high at 8 or 10 pF.

Tom Dagostino
Teraspeed Consulting Group LLC
503-430-1065
tom@teraspeed.com
www.teraspeed.com

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of RODRIGUEZ_LECONA_RAMIRO
Sent: Thursday, August 05, 2004 4:35 PM
To: ibis-users@eda.org
Cc: ibis-info@eda.org
Subject: [IBIS-Users] C_comp values

 Hi, I am using some buffers models and I have a question:

       Is C_comp value for input structure greater than for I/O or Output
structure? This question is because some vendors specify the same values for
both structures.
       Are there limits for C_comp values? Does IBIS standard specify
limits?
       What are typical values for C_comp (input structure and I/O
structure)?

    Thanks for your answer

Regards,

  Ramiro Lecona
|------------------------------------------------------------------
|For help or to subscribe/unsubscribe, email majordomo@eda.org
|with just the appropriate command message(s) in the body:
|
| help
| subscribe ibis <optional e-mail address, if different>
| subscribe ibis-users <optional e-mail address, if different>
| unsubscribe ibis <optional e-mail address, if different>
| unsubscribe ibis-users <optional e-mail address, if different>
|
|or email a written request to ibis-request@eda.org.
|
|IBIS reflector archives exist under:
|
| http://www.eda.org/pub/ibis/email_archive/ Recent
| http://www.eda.org/pub/ibis/users_archive/ Recent
| http://www.eda.org/pub/ibis/email/ E-mail since 1993

|------------------------------------------------------------------
|For help or to subscribe/unsubscribe, email majordomo@eda.org
|with just the appropriate command message(s) in the body:
|
| help
| subscribe ibis <optional e-mail address, if different>
| subscribe ibis-users <optional e-mail address, if different>
| unsubscribe ibis <optional e-mail address, if different>
| unsubscribe ibis-users <optional e-mail address, if different>
|
|or email a written request to ibis-request@eda.org.
|
|IBIS reflector archives exist under:
|
| http://www.eda.org/pub/ibis/email_archive/ Recent
| http://www.eda.org/pub/ibis/users_archive/ Recent
| http://www.eda.org/pub/ibis/email/ E-mail since 1993
Received on Thu Aug 5 18:04:10 2004