AW: different rising and falling Ramp dV

The ibis models do only have the same value of dV, if the load AND the
termination voltage have the same value.
The ibis-ramp termination voltage is defined for
rising: 0V
falling: vcc

But you can get the exact dV out of the pullup and pulldown-curves.

Katja

> -----Urspr> üngliche Nachricht-----
> Von: Mike LaBonte [SMTP:mike@labonte.com]
> Gesendet am: Freitag, 23. März 2001 00:19
> An: ibis-users@vhdl.org
> Betreff: different rising and falling Ramp dV
>
> Many IBIS models have different values for dV in the dV/dt_r and dV/dt_f.
> The clipping below from IBIS spec shows an example. But the usage rules
> imply that dV must be 60% of the voltage swing. If the voltage swing is
> measured between the 2 steady-state voltages, then how could you have
> different values for rise and fall dV? If there is variation in how
> simulators handle the Ramp dV values, then this may matter.
>
> Mike LaBonte
>
> |=============================================================================
> | Keyword: [Ramp]
> | Required: Yes, except for inputs, terminators, Series and Series_switch
> | model types.
> | Description: Defines the rise and fall times of a buffer. The ramp rate
> | does not include packaging but does include the effects of the
> | C_comp parameter.
> | Sub-Params: dV/dt_r, dV/dt_f, R_load
> | Usage Rules: The rise and fall time is defined as the time it takes the
> | output to go from 20% to 80% of its final value. The ramp
> | rate is defined as:
> |
> | dV 20% to 80% voltage swing
> | -- = ----------------------------------------
> | dt Time it takes to swing the above voltage
> |
> | The ramp rate must be specified as an explicit fraction and
> | must not be reduced. The [Ramp] values can use "NA" for the
> | min and max values only. The R_load subparameter is optional
> | if the default 50 ohm load is used. The R_load subparameter
> | is required if a non-standard load is used.
> |-----------------------------------------------------------------------------
> [Ramp]
> | variable typ min max
> dV/dt_r 2.20/1.06n 1.92/1.28n 2.49/650p
> dV/dt_f 2.46/1.21n 2.21/1.54n 2.70/770p
> R_load = 300ohms
 
Received on Fri Mar 23 01:01:10 2001