RE: [IBIS-Users] Bus Switch IBIS Models

Hi Arpad,

That was my assumption as well. It seems an [R Series] would be sufficient
but I suppose with [Series Current] you could have the leakage current.

For anyone interested I did put together a short article about IBIS switch
modeling that can be found at
http://www.sharksim.com/articles/ibis_analog_series_bus_switches.html. I
tried to give a little background on analog switches and a couple of
different ways you can model them in IBIS. The article is not complete yet
as I still have some additional correlation data to add but it's a good
start. Feel free to comment in this email thread or contact me off line.

Thanks to everyone who responded on and off line

Best

Tim

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of Muranyi, Arpad
Sent: Monday, October 25, 2010 8:03 PM
To: IBIS
Subject: RE: [IBIS-Users] Bus Switch IBIS Models

Tim,

It all depends on the device, but in the off state I

would not expect it to have any significant series

current that you would need to model with [Series

Current]. Series bus switches are usually in a fairly

high impedance state when they are turned off.

Arpad

=======================================================

From: Timothy Coyle [mailto:tim.coyle@siconsultant.com]
Sent: Friday, October 22, 2010 12:50 PM
To: 'Mike LaBonte'; Muranyi, Arpad; 'IBIS'
Subject: RE: [IBIS-Users] Bus Switch IBIS Models

How about when the switch is in the Off state. Is there a situation where
you need to simulate that with actual data such as [Series Current] or is [R
Series] sufficient? Does the EDA tool just need a way to disable the switch
in a batch mode type simulation?

Thanks

Tim

From: Mike LaBonte [mailto:milabont@cisco.com]
Sent: Friday, October 22, 2010 11:04 AM
To: Arpad Muranyi; Timothy Coyle; IBIS
Subject: Re: [IBIS-Users] Bus Switch IBIS Models

More exactly, IBIS does not have time profile data to model the transition
of a series switch between on and off states. It is certainly possible to
convert the IBIS series switch model data to a circuit model using table
elements, in which a control signal makes the switch transition dynamically
from on to off and vice-versa. The switching time profile would have to be
set by the control signal. I believe the Cadence implementation works this
way, but I have heard of only one instance of someone using the capability
(experimentally).

I agree with Tim that automation of [Series Switch Groups] and on/off
control at the EDA tool end is lacking. I think Tim is asking the right
question, "does anyone really need it?"

Mike

On 10/22/10 10:25 AM, "Arpad Muranyi" <Arpad_Muranyi@mentor.com> wrote:

Tim,
 
IBIS doesn't support modeling the transitions between the On/Off state.
The assumption is that this is not changing during simulations. There
is no information in the models that describes how these devices would
transition from one state to the other. We would need something like
the V-t tables in order to do that, but they don't exist for this
purpose.
 
Arpad
=======================================================================
 

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of Timothy Coyle
Sent: Thursday, October 21, 2010 11:35 AM
To: ibis-users@eda.org
Subject: [IBIS-Users] Bus Switch IBIS Models

Hi,
When you have MOSFET switch and model it using [Series Mosfet] keyword in
IBIS there are two ways to pin map it. The first way is to use [Model]
Series and just use [Series Pin Mapping] and this assumes that the switch is
always in On state. The other way is to use [Model] Series_switch with
[Series Pin Mapping] and [Series Switch Groups] and this way there can be
configured On and Off states. However I have found that most simulation/cad
tools do not fully support [Series Switch Groups] without manual
modification by end user. Modeling the switch as a Series device just Series
Pin Mapping seems to be the default supported state.
 
Has anyone else seen this issues of Series Switch Groups not being
supported? Even when I do some modifications for a tool to support it many
do not seem to use the Off state data. I would also be interested to hear of
the simulation usage case where someone needs the ability to switch between
On and Off states.
 
Thanks,
 
Timothy Coyle
President
Signal Consulting Group LLC
405 Western Ave #430
South Portland, ME 04106
Tel: 617.297.2566
Email: tim.coyle@siconsultant.com <mailto:tim.coyle@siconsultant.com>
Web: http://www.siconsultant.com <http://www.siconsultant.com/>
SharkSim <http://www.sharksim.com/> - Signal Integrity IBIS Modeling
Software

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