Re: ecl models in ibis

Nik:

Answers to your questions are in your text.

Bob Ross
Mentor Graphics

> From: nikolai@avanticorp.com
> Date: Fri, 13 Nov 1998 14:26:48 -0800 (PST)
> Message-Id: <199811132226.OAA28977@iris.src.avanticorp.com>
> To: ibis-users@eda.org
> Subject: ecl models in ibis

> IBIS Gurus, Experst, Inventors, and Developers:

> Can anybody clarify the following ECL model related issues in IBIS.
> Below is an excerpt from IBIS file (downloaded from internet).
> I have 2 questions regasrding these data.

> 1) Why current in PU/PD tables is always negative? Why
> the buffer "ECL_OBUF3_5" always source current and never sink current?
> Is this something "ECL_OBUF3_5" model specific or it is a typical case for
> Output_ECL buffer?

The currents are negative because they follow the polarity convention
that currents are positive when they are flowing into the pin. Output_ECL
buffers typically source current in both the high and low stages.

> 2) regarding:

> [Voltage Range] 0.0 0.0 0.0
> [Pulldown Reference] 0.0 0.0 0.0
> [Power Clamp Reference] 0.0 0.0 0.0
> [GND Clamp Reference] -3.3 -3.0 -3.8

> Why [Pulldown Reference] = 0, why not to use [Pulldown Reference] = -3.3V ?

The IBIS Spec set the reference voltage for BOTH the Pulldown and Pullup
tables to the highest rail - in this case 0 Volts. So this table follows
the Standard.

> THis question is more about conventions used.
> It is clear what voltages are applied. Why not to use notations:

> [Voltage Range] 0.0 0.0 0.0
> [Pullup Reference] 0.0 0.0 0.0 (*)
> [Pulldown Reference] -3.3 -3.0 -3.8
> [Power Clamp Reference] 0.0 0.0 0.0 (*)
> [GND Clamp Reference] -3.3 -3.0 -3.8

> (*) indicate optional parameter (no need to include it, but no harm if it is
> given)

We did treat the ECL case as different. thus the conventions you suggest
do not work.

> Thank you

> Nik

> nikolai@avanticorp.com
Received on Fri Nov 13 18:32:21 1998