Subject: RAMP NOTE

From: [email-masked] ( Bob Ross)
Date: Tue, 1 Feb 94 17:29:41 PST

Dear IBIS folks:

Here is how I interpret the [Ramp] specification in IBIS Version 1.1.
This interpretation is based on two factors:

(1) The NOTES ON DATA DERIVATION METHOD specify that the dv/dt_r and
dV/dt_f variables be derived from the 20% and 80% points of a rising
and falling transition under the loads specified (spanning 0.6 of the
full voltage transition).

(2) The time durations can be assumed to be the same for any resistive
load (as a first order approximation).  This was mentioned at the IBIS
Summit in November.

Therefore, if the [Ramp] specification is to be translated into a 0% to
100% time ramp (such as in the Spice PULSE specification) then the 
translation is as follows:

                    trise(0-100%) = (dt_r)/.6
                    tfall(0-100%) = (dt_f)/.6

For example, the numbers in IBIS Version 1.1 translate as shown:

|-----------------------------------------------------------------------
[Ramp]
| variable      typ             min             max
dV/dt_r         4.2/1.8n        3.5/2.5n        5.0/1.1n
dV/dt_f         2.5/1.5n        2.0/2.3n        3.0/0.8n
|=======================================================================

trise(0-100%)    3.00n           4.17n           1.83n
tfall(0-100%)    2.50n           3.83n           1.33n

Bob Ross,
Interconnectix, Inc.