RE: [IBIS-Users] difference between [Pullup Reference] and [Voltage Range]

IBIS voltages only are concerned with the voltage applied to the output or
input stage (that may be changing with some of the new birds being
discussed).  They define which rail, voltage, the currents will flow into or
out of.  For an output the Voltage Range key word will tell the simulator
what supply voltage the output's pullup will supply current from and what
supply voltage the power clamp if present will dump current into.  If there
is a Pullup Reference and a Powerclamp Reference stated in the model then
first, they describe the power supply that sources current for the pullup
and power supply that sinks current for the clamp.  In this case the
Powerclamp Reference and be different than the Pullup Reference.  A good
example of this would be a 3.3V output buffer (Pullup Reference) that is 5
Volt compatible with a Powerclamp Reference of 5.0 Volts.

It is unlikely that your example would ever occur.  If your Pullup Reference
is 2.5V your Voltage Range, the operating is not 1.2 Volts.  The core supply
voltage should not be in the model, it is not sinking or sourcing currents
in the input or output stage.

Tom Dagostino
Teraspeed Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
http://www.teraspeed.com
tom@teraspeed.com

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827

Teraspeed is the registered service mark of
Teraspeed Consulting Group LLC

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of Akhilesh CHANDRA
Sent: Thursday, April 21, 2005 6:56 AM
To: ibis; ibis-users
Cc: Akhilesh CHANDRA
Subject: [IBIS-Users] difference between [Pullup Reference] and [Voltage
Range]


>
>
Hello Friends,

 As I read in IBIS standard

Voltage Range----Defines the power supply voltage tolerance over which
the model is intended to operate.
Pullup Reference--Defines a voltage rail other than that defined by the
[Voltage  Range] keyword as the reference voltage for the [Pullup] I-V
data.
  My buffer have dual supply VDD and VDDE2V5. VDD is the core side
supply and VDDE2V5 voltage at the pad as well as voltage at the pullup
and power clam diode.

 I wnat to know how this information is use in the simulation.
 When pullup information is present then it's overwrite voltag information?

I have given
[Voltage Range]  1.2 1.1 1.3
[Pullup Reference] 2.5 2.2 2.7

   Which information is used in the simulation.

Regards
Akhilesh

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