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

From: Bob Ross <bob_at_.....>
Date: Thu Apr 28 2005 - 10:06:41 PDT
Hi Akhilesh:

The Specification may be slighly confusing in this area, but here
are the the intended rules:

1. All four [* Reference] rails are required if [Voltage Range]
missing.  Otherwise [Voltage Range] is required.  (This rule
overreaches for rule statement simplicity reasons.)

2. [Voltage Range] only is acceptable (legacy reasons)

3. Your issue: [Voltage Range] with any or all of the [* Reference]
rails are permitted

  - Each specified [* Reference] rail should be used.  The [Voltage
    Range] and absolute 0 V GND should be considered a default value
    only if the [* Reference] is missing.  Here is some of the text:

|=============================================================================
|     Keyword:  [Voltage Range]
|    Required:  Yes, if [Pullup Reference], [Pulldown Reference], [POWER
|               Clamp Reference], and [GND Clamp Reference] are not present
| Description:  Defines the power supply voltage tolerance over which the
|               model is intended to operate.  It also specifies the default
|               voltage rail to which the [Pullup] and [POWER Clamp] I-V data
|               is referenced.
| Usage Rules:  Provide actual voltages (not percentages) in the typ, min, max
|               format.  "NA" is allowed for the min and max values only.
| Other Notes:  If the [Voltage Range] keyword is not present, then all four
|               of the keywords described below must be present: [Pullup
|               Reference], [Pulldown Reference], [POWER Clamp Reference],
|               and [GND Clamp Reference].  If the [Voltage Range] is present,
|               the other keywords are optional and may or may not be used as
|               required.  It is legal (although redundant) for an optional
|               keyword to specify the same voltage as specified by the
|               [Voltage Range] keyword.
|-----------------------------------------------------------------------------

Comment - it is also legal to for [Voltage Range] and the other keywords
to specify different voltages because no restriction is stated.


|=============================================================================
|     Keyword:  [Pullup Reference]
|    Required:  Yes, if the [Voltage Range] keyword is not present
| Description:  Defines a voltage rail other than that defined by the [Voltage
|               Range] keyword as the reference voltage for the [Pullup] I-V
|               data.
| Usage Rules:  Provide actual voltages (not percentages) in the typ, min, max
|               format.  "NA" is allowed for the min and max values only.
| Other Notes:  This keyword, if present, also defines the voltage range over
|               which the typ, min, and max dV/dt_r values are derived.
|-----------------------------------------------------------------------------

Comment - not well worded, but the description should be interpreted as
defining the voltage rail regardless of any (if it exists) [Voltage Range]
entry.

|=============================================================================
|     Keyword:  [Pulldown Reference]
|    Required:  Yes, if the [Voltage Range] keyword is not present
| Description:  Defines a power supply rail other than 0 V as the reference
|               voltage for the [Pulldown] I-V data.  If this keyword is not
|               present, the voltage data points in the [Pulldown] I-V table
|               are referenced to 0 V.
| Usage Rules:  Provide actual voltages (not percentages) in the typ, min, max
|               format.  "NA" is allowed for the min and max values only.
| Other Notes:  This keyword, if present, also defines the voltage range over
|               which the typ, min, and max dV/dt_f values are derived.
|-----------------------------------------------------------------------------

Comment - Here the value is used (overriding the default reference of 0 V.

Bob


Akhilesh CHANDRA wrote:
> 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
>>>
>>
>>>
>>>
>>
> 
> 
> 

-- 
Bob Ross
Teraspeed Consulting Group LLC     Teraspeed Labs
121 North River Drive              13610 SW Harness Lane
Narragansett, RI 02882             Beaverton, OR 97008
401-284-1827                       503-430-1065
http://www.teraspeed.com           503-246-8048 Direct
bob@teraspeed.com

Teraspeed is a registered service mark of Teraspeed Consulting Group LLC


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Received on Thu Apr 28 10:06:08 2005

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