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

Akhilesh,

We agree with your view, and we are making improvements to Hyperlynx
behavior with the voltage reference keywords to more strictly follow the
IBIS specification and avoid confusing results versus other tools.

There remains the point raised by Tom Dagostino: Models are unlikely to
need both [Voltage Range] and [Pullup Reference] keywords with different
values.  Certainly not the particular case you raised, because core
supply voltage should not be in the model.  

In general, if you do need to mix voltage references within the model,
be careful how you do it.  Remember that according to the IBIS
specification, [Voltage Range] still defines the power clamp reference
unless a [POWER Clamp Reference] keyword overrides it.  In the case you
gave, [Voltage Range] defines the power clamp reference to be 1.2 V,
versus a [Pullup reference] value of 2.5 V!  If the pullup and power
clamp references need to be different, it is clearly better to use the
[POWER Clamp Reference] keyword, and probably best to use all four [*
Reference] keywords explicitly.

Best regards,

John Angulo
Software Development Engineer
Hyperlynx Products
Mentor Graphics Corp.

> -----Original Message-----
> From: owner-ibis-users@eda.org 
> [mailto:owner-ibis-users@eda.org] On Behalf Of Akhilesh CHANDRA
> Sent: Wednesday, April 27, 2005 9:41 PM
> To: Bob Ross
> Cc: tom@teraspeed.com; ibis; ibis-users
> Subject: Re: [IBIS-Users] difference between [Pullup 
> Reference] and [Voltage Range]
> 
> Hello Bob,
> 
>   Yes, I think ELDO and HSPICE override voltage range while 
> in HYPERLYNX it does't, befor this I validate my models 
> through ELDO and HSPICE now I switch to HYPERLYNX and find 
> out this problem .
>   In HYPERLYNX if keyword voltage range, power Clamp 
> Reference and Pullup Reference are presents then it take 
> volatge range keywords for simulation. In my view if optional 
> keywords are present then it should read from optional keywords.
> 
> Regards
> Akhilesh
> 
> Bob Ross wrote:
> 
> > Hello Akhilesh:
> >
> > In some tool, the [Pullup Reference] and/or the [Power Clamp 
> > Reference] will override the [Voltage Range].
> >
> > Bob
> >
> > Tom Dagostino wrote:
> >
> >> 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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