Subject: Rising/Falling waveform and Ramp keywords

From: Offer Kaye <[email-masked]>
Date: Sat, 9 Dec 2000 15:16:57 +0200 (IST)

Hello IBIS gurus.
My question is this- in the IBIS spec, the Rising/Falling Waveform
keywords include the sub-parameters R/L/C/V_fixture and R/L/C_dut, while
the Ramp keyword does not.
I want to measure these parameters (from a packaged component), and I
don't understand why the difference in specs for keywords which it was my
understanding should be measured the same way (only different data used).

How should my test setup be different for the Waveforms vs. Ramp
measurements? Can someone explain in greater detail (than the spec) the
meaning of the R/L/C/V_fixture subparameters?

Thanks in advance,
Offer Kaye
[email-masked]

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From: "Muranyi, Arpad" <[email-masked]>
Date: Fri, 15 Dec 2000 11:33:13 -0800

Alan,

50 Ohm is not required only if you make an IBIS1.1 model.
In IBIS version 2.1 and above you can use anything you want,
you just have to specify what you used in the R_fixture and/or
R_load sub-parameters.

Arpad Muranyi
===========================================================

-----Original Message-----
From: Alan Hilton-Nickel [mailto:[email-masked]]
Sent: Friday, December 15, 2000 11:20 AM
To: Peters, Stephen
Cc: [email-masked]
Subject: Re: Rising/Falling waveform and Ramp keywords

"Peters, Stephen" wrote:
> Note that for a standard CMOS buffer the cookbook recomends including four
> waveforms: two rising, one with the buffer driving 50 ohms to VCC and
> another with the buffer driving 50 ohms to gnd, and two falling, same
> conditions.  For more info, check out the IBIS cookbook at
> 

Stephen,

I am a little uncomfortable with specifying a waveform into a 50 ohm
load, when we tell our customers to use a 60 ohm characteristic
impedance on their board. Would it screw the IBIS modeller up if we gave
a waveform into a 60 ohm load? I would think it would be more
representative (if not more accurate) of what the driver would see in
normal use.

Alan Hilton-Nickel
Transmeta Corp

---

From: "Peters, Stephen" <[email-masked]>
Date: Fri, 15 Dec 2000 11:39:35 -0800

Hi Alan:

The 50 ohm load is a recommendation based on a "standard" CMOS buffer.  If
you are specifically specing your drivers to work into a 60 ohm load, then
by all mean -- take the ramp and V-T waveform data into 60 ohms. It
definatly shouldn't make the model invalid or cause the simulator tool
problems, as long as the load resistance under which the [Ramp] and V-T is
taken is documented properly (the R_load and R_fixture subparmeters
respectivly). 

  Regards,
  Stephen

-----Original Message-----
From: Alan Hilton-Nickel [mailto:[email-masked]]
Sent: Friday, December 15, 2000 11:20 AM
To: Peters, Stephen
Cc: [email-masked]
Subject: Re: Rising/Falling waveform and Ramp keywords

Stephen,

Alan Hilton-Nickel
Transmeta Corp