(no subject)

Hello, IBISians !

I want to use IBIS for modeling of Ground/Power Noise of simultaneously
switching drivers.
Spec version 2.1 can handle static V/I curves and Vout(t) curves
for a given load. If I've got this information then I am able to
determine the rising/falling waveform of the output current Iout(t)
of a switching driver.

What I need for example to calculate the voltage drop over the
ground inductance L_gnd_pin (see below) is the contribution of every
(simultaneously) switching driver to the current I_gnd(t) flowing
through their common ground pin inductance (if I assume for
simplification that the inductance of the ground path is caused only
by that ground pin).

                         o PWR
                         |
                         |
                         C
                         C L_pwr_pin
                         C
                         |
                         |
                         V I_pwr(t)
       I_pwr_1(t) | I_pwr_n(t)
                         |
     -----<--------------*------------- - - ----->---
     | | |
     | V I_pwr_2(t) |
     | | |
---------- ---------- ----------
| | Iout_1(t)| | Iout_2(t) | | Iout_n(t)
|Driver_1| |Driver_2| |Driver_n|
| |--->-| | |--->--| | |--->--|
| | | | | | | | |
---------- --- ---------- --- ---------- ---
     | --- CL_1 | --- CL_2 | CL_n ---
     | | | | | |
     | | | | | |
     | --- | --- | ---
     | | |
     V I_gnd_1(t) V I_gnd_2(t) V I_gnd_n(t)
     | | |
     | | |
     --------------------*-------------- - - --------
                         |
                         |
                         V I_gnd(t)
                         |
                         C
                         C L_gnd_pin
                         C
                         |
                         |
                        ---

It would be useful for Ground/Power Noise calculations to have the
currents of the internal ground/power path of every driver
I_gnd_1(t)/I_pwr_1(t) ... I_gnd_n(t)/I_pwr_n(t) with respect to
the corresponding Vout(t) curves for specified loads.

Unfortunately it is not possible to describe these ground/power path
currents with current IBIS format in my opinion. I'm quite aware
of the fact that this request perhaps contradicts the basic
concept of IBIS because these internal ground/power path currents are
not measurable from outside of the package.

But at my point of view I don't see any other way for an
efficient ground (power) noise analysis.

However, what do you think about the opportunities to model
power/ground noise and the resulting switching noise at the
outputs of active/quiescent output buffers by using present
or future IBIS format ?

Any comments to that problem will be appreciated.

Thank you very much in advance

Michael Gutzmann

Cadlab
Group Analog System Engineering
Joint R&D Institute
University of Paderborn
Siemens Nixdorf Informationssysteme AG
Fuerstenallee 7
33102 Paderborn
Germany

phone: +49-5251-60-6164
fax : +49-5251-60-6155
e-mail: micha@cadlab.de
Received on Mon Oct 23 02:15:24 1995