Subject: Use of [Ramp] keyword

From: FITZPATRICK John <[email-masked]>
Date: Wed, 15 May 1996 12:07:55 +0200

Hello all,

A short question regarding interpretation of a model:

In the IBIS 2.1 spec, the ramp rate is defined as

  dV         20% to 80% voltage swing
  --  = --------------------------------------
  dt    Time to take to swing the above voltage

When I scan through a random set of IBIS models, I see the
following entries after the [Ramp] keyword of the following
types:

a)     dV/dt_r      1.84/0.65n 1.77/0.65n 1.87/0.53n

b)     dV/dt_r         4.1/1n          1.6/1n          8.2/1n

From my point of view, a) is correct, but b) is not good.

I would like to be able to extract dV and dt individually.
As [Ramp] is an obligatory keyword, I hoped it would be
safe to do so .... until I saw b).

Thanks for your help,
John

-- 
John Fitzpatrick   <[email-masked]>    
Alcatel CIT, 4 rue de Broglie, 22304 Lannion, France
Tel: (+33)96.04.79.33  Fax: (+33)96.04.85.09

---

From: [email-masked] (Jon Powell)
Date: Wed, 15 May 96 07:47:11 PDT

>>>>> "FITZPATRICK" == FITZPATRICK John <uunet!ln.cit.alcatel.fr!John.Fitzpatrick> writes:

    FITZPATRICK> Hello all, A short question regarding interpretation
    FITZPATRICK> of a model:

    FITZPATRICK> In the IBIS 2.1 spec, the ramp rate is defined as

    FITZPATRICK>   dV 20% to 80% voltage swing -- =
    FITZPATRICK> -------------------------------------- dt Time to
    FITZPATRICK> take to swing the above voltage

    FITZPATRICK> When I scan through a random set of IBIS models, I
    FITZPATRICK> see the following entries after the [Ramp] keyword of
    FITZPATRICK> the following types:

    FITZPATRICK> a) dV/dt_r 1.84/0.65n 1.77/0.65n 1.87/0.53n

    FITZPATRICK> b) dV/dt_r 4.1/1n 1.6/1n 8.2/1n

    >> From my point of view, a) is correct, but b) is not good.

    FITZPATRICK> I would like to be able to extract dV and dt
    FITZPATRICK> individually.  As [Ramp] is an obligatory keyword, I
    FITZPATRICK> hoped it would be safe to do so .... until I saw b).

    FITZPATRICK> Thanks for your help, John

You are right, b is probably meaningless (unless the risetime happens to
be 1ns. What model was this in?

Jon