Subject: [IBIS-Users] RE: IBIS Question
From: Lynne Green (lgreen@cadence.com)
Date: Tue Jul 15 2003 - 09:23:01 PDT
Hello, Naftali,
In the future, please post your questions to the IBIS reflector
(ibis-users@eda.org). You will get faster replies, and from the best
experts.
As a general rule, V-t curves are used for actual simulations, while
[Ramp] values are used for analytic algorithms.
The IBIS spec recommends that V-t tables be generated without R_dut,
L_dut, and C_dut.
Best regards,
Lynne
-----Original Message-----
From: Naftali.Refaeli@ecitele.com [mailto:Naftali.Refaeli@ecitele.com]
Sent: Tuesday, July 15, 2003 3:28 AM
To: Lynne Green
Subject: IBIS Question
Hello Lynne.
May I ask an IBIS V-T question?
Look at the following V-T data:
|***********************************************************************
|*************************
|
[Ramp]
| variable typ min max
dV/dt_r 1.52/0.81n 1.45/0.83n 1.56/0.81n
dV/dt_f 1.43/0.68n 1.38/0.69n 1.46/0.71n
R_load = 50.00
|
[Rising Waveform]
R_fixture = 50.00
V_fixture = 0.000
C_fixture = 10.00pF
R_dut = 4.77m
L_dut = 6.95nH
C_dut = 8.66pF
| time V(typ) V(min) V(max)
|
0.000S 0.000V 0.000V 0.000V
1.000e-10S -42.220uV -42.220uV -71.850uV
0.200nS -0.501mV ...
|***********************************************************************
|*************************
The IBIS "[Ramp] dtr" value is ~800pSec, while [Rising Waveform] shows
about 1.2nsec Rise time. This is - of course - because of loading the
I/O by C_fixture = 10.00pF, R_dut = 4.77m, L_dut = 6.95nH, C_dut =
8.66pF
But - how the simulator use the [Rising Waveform] data ?
Does the simulator calculate "real" t_rise by using both [Ramp] and V-T
table, or it presume that V-T data is more accurate for that
calculation?
(Embedded image moved to file: pic18969.pcx)
*****************************************
Naftali Refaeli
Analog & High Speed Applications.
EDS-ECI
30 Hasivim St.
Petah-Tikva 49133 Israel
Tl. +972-3-9266973 Fax: +972-3-9268188
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