[IBIS-Users] The buffer have a outside terminal: Pls teach me modeling method


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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