RE: [IBIS-Users] R_load, R_ref and R_fix

YY,

I can give you a hand with the terminology, at least.  The terms you
mention have the following meanings:

R_fixture specifies the resistance used in the "test fixture" loading
the buffer when the V-t tables were generated.  In other words,
R_fixture should correspond to the value of the resistor connected to
the buffer when you ran your V-t sims. You will find this used under the
[Rising Waveform] and [Falling Waveform] keywords in IBIS.

R_load is an optional subparameter which specifies the resistance used
in the "test fixture" loading the buffer when the [Ramp] values were
generated.  It is similar to R_fixture (i.e., a resistive load used for
generation of transient table data), but is used in a completely
different context.  If not specified, R_load defaults to 50 ohms.

R_ref is the resistance used in the delay fixture used for timing
purposes, such as calculating output switching time or derating
propagation delay.  This subparameter is located under the [Model]
keyword in IBIS.  It does NOT affect the output of your buffer per the
I-V and V-t tables, but may affect how your system simulation results,
particularly timing spreadsheets, are calculated.

I hope this helps!

- Michael Mirmak
  Intel Corp.
  Chair, EIA IBIS Open Forum

________________________________

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of lau yy
Sent: Wednesday, June 22, 2005 3:31 AM
To: ibis-users@eda.org
Subject: [IBIS-Users] R_load, R_ref and R_fix

Dear ALL,
 
I am a bit confused with these 3 term. R_LOAD, R_REF and R_FIX.
 
Can anyone help me on this?
 
Another question :
 
If I need a R_load (requested) = 50 ohm. Is that mean I need to add it
in the schematic and also in the .s2i file under keyword [R_load]. Then,
run the simulation.
 
or
 
I only need to add in keyword [R_load] in the .s2i file then the machine
will automatic take it in count.
 
Thanks
 
rdgs 
yylau

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