RE: [IBIS-Users] differential receiver ibis model

I would suggest to do the same sweep range in order to
be able to do the subtraction correctly (-Vcc to 2*Vcc).

However, you may have difficulty to get the simulation
to converge at the ends of the range, especially if
you want to start there.  In order to help that, I
usually start at 0 volt or at Vcc (depending on whether
I do my sweep GND or Vcc relative), then go to the end
of the sweep range, and then do the sweep.  The first
portion of the data that contains the results of going
from 0 or Vcc to the end of the sweep range can be
discarded.

Arpad
=========================================================

-----Original Message-----
From: Raghavendra M [mailto:mraghav@pulsecoresemi.com] 
Sent: Thursday, September 10, 2009 10:00 PM
To: Muranyi, Arpad
Cc: ibis-users@eda.org
Subject: Re: [IBIS-Users] differential receiver ibis model

Hi Muranyi Arpad,

Thank you very much for your reply.
Is the sweep voltage ranges for differential buffer same as normal 
3-state buffer?(i.e., -VDD to 2*VDD or 0 to VDD). If my suplly voltage 
is 1.8V, then sweep range is -1.8 to 3.6 or its different.
(sweep voltage range is voltage range of the positive and negative 
terminals of the fully differential buffer)

Thanks & Regards
Raghavendra M

Muranyi, Arpad wrote:
> Raghavendra,
>
> The common mode current goes into the normal [Model]'s
> I-V tables, and the differential current goes into the
> series model that is placed between the two [Model]-s.
> You can further separate the clamp currents from the
> PU and PD I-V curves in the [Model] by redoing the
> same measurements in a 3-stated mode.  (But don't
> forget to put the difference of the clamp and driven
> I-V curves into the PU and PD tables, instead of the
> total current to avoid double counting).
>
> I am not aware of a tool that can do all this in
> an automated way.
>
> Arpad
> =======================================================
>
> -----Original Message-----
> From: owner-ibis-users@server.eda.org
> [mailto:owner-ibis-users@server.eda.org] On Behalf Of Raghavendra M
> Sent: Thursday, September 10, 2009 12:17 AM
> To: ibis-users@server.eda.org
> Subject: [IBIS-Users] differential receiver ibis model
>
> Hi,
>
> I have a fully differential receiver in a chip, am trying to make an 
> ibis model for this receiver
> Can you describe the method how to generate an ibis v3 model for the 
> differential receiver
> I read the ibis cookbook and it says that for a differential buffer
with
>
> positive and negative inputs,
> one input should be swept keeping the other input constant(negative)
and
>
> record the currents into both inputs.
> Now change the constant input to new value and sweep the positive
input 
> and record the currents.
> This process should be continued as the negative input is swept in
steps
>
> through the  same range  as positive input.
>  From the current recorded we have to separate common mode and 
> differential mode currents.
> But my question is where should we keep this common mode and 
> differential mode currents in the ibis file?
> Actually for receiver, only clamp data should be kept in ibis file, so

> in [Power clamp] data where should we keep
> common mode current and differential mode current
>
> Should i use series model for my differential receiver?
> Should we place these characteristics in the model series?
> Is there any tool to generate an ibis model for differential receiver 
> directly?
>
> Thanks & Regards
> Raghavendra M
>
>
>   


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