Subject: [IBIS-Users] The buffer have a outside terminal: Pls teach me modeling method
From: Takanobu Ura (t-ura@pb.jp.nec.com)
Date: Mon Jun 10 2002 - 04:01:56 PDT
Dear All,
Regarding IBIS modeling method, In case of the buffer have a outside pullup
terminal, Do we need to analyze with waveform-SPICE-netlist including outside
pullup terminal?
For example, HSTL buffer is used as follows:
Buffer terminal Transmission line
-----><-------><--------
Vdd/2 Vdd/2
-+- -+-
| |
R R
| R=50ohm |
|>---+------/////-----------+---|>
We analyzed as follows:
V-I table
|>--------------+
|
V External Voltage Sweep
|
/// GND
V-t table
RisingWaveform/FalingWaveform
VDD/2
-+-
|
R1 V_fixture=Vdd/2
| R_fixture=R1
Vin-|>-----+
When we generate IBIS-model with above the SPICE-netlist, Ibischk3 reports
the below error message:
ERROR - Model HSTL1: The [Rising Waveform]
with [R_fixture]=50 Ohms and [V_fixture]=1.5V
has TYP column DC endpoints of 0.00V and 1.29v, but
an equivalent load applied to the model's I-V tables yields
different voltages ( 0.16V and 1.50V),
a difference of 100.00% and 14.00%, respectively.
Please let me know modeling method which the buffer have a outside pullup
terminal.
Best regards,
T.Ura
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