Re: [IBIS-Users] Usage of [Series Current]

From: Bob Ross <bob_at_.....>
Date: Wed Sep 23 2009 - 18:09:11 PDT
Hi Prabhat:

Below is the picture for reference.


|
|                                Table Current
|                                   ------>
|                             +  Table Voltage  -
|                          Pin 1  |---------|  Pin 2
|                             <---+         +--->
|                                 |---------|
|
|               C_comp values are ignored for [Series Current] models.
|-----------------------------------------------------------------------------
[Series Current]
|  Voltage   I(typ)    I(min)    I(max)
    -5.0V  -3900.0m  -3800.0m  -4000.0m
    -0.7V    -80.0m    -75.0m    -85.0m
    -0.6V    -22.0m    -20.0m    -25.0m
    -0.5V     -2.4m     -2.0m     -2.9m
    -0.4V      0.0m      0.0m      0.0m
     5.0V      0.0m      0.0m      0.0m
|

The voltage table convention defines the drop from Pin 1 to Pin 2.  So a
negative table voltage means that the voltage at Pin 2 is higher than
Pin 1.  The current flow convention might be restated that the current
flowing into Pin 1 (and through the series element to Pin 2) is positive.
That is consistent with the current flow convention for other keywords
and for SPICE.

The example represents a series diode whose on state is when the
Pin 2 voltage is greater than Pin 1 voltage, and whose off state
is just the opposite.  So I think the signs are correct.

Also, as previously indicated, you probably need to extend the series
current voltage table to both the plus and minus voltage directions.
That should avoid ambiguity regarding how tools might handle currents
for voltage drops that are not specified in the table.

Bob

Prabhat RANJAN wrote:
> Hello Mike n Experts,
> 
>  
> 
> Regarding the direction of current, you have mentioned that ? currents 
> into pin 2 would be negative. It should not be necessary??.
> 
>  
> 
> For which condition, above convention would not be valid??
> 
>  
> 
>  
> 
> Also, For any positive voltage in V-I table of [Series Current] ( i.e., 
> voltage of pin 1 is greater than pin2 ) , current will come out from pin 
> 1 and will go into pin 2 and from Defined convention of [Series 
> keyword], sign of current will be negative.
> 
> Similarly, for negative voltage, current will be positive.
> 
>  
> 
> But, example given under keyword [Series Current] in IBIS ver5.0 
> specification document shows negative current for negative voltage.
> 
>  
> 
>  
> 
> Am I interpreting the ?current direction convention? wrongly or there is 
> some discrepancy in SPECIFICATION document??
> 
>  
> 
>  
> 
> Regards
> 
>  
> 
> PRABHAT
> 
>  
> 
>  
> 
> From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On 
> Behalf Of Mike LaBonte (milabont)
> Sent: Monday, September 14, 2009 6:32 PM
> To: Edward Rose; ibis-users@server.eda.org; ibis@server.eda.org
> Subject: [IBIS] RE: [IBIS-Users] Usage of [Series Current]
> 
>  
> 
> The series models below do appear to be equivalent. Voltage on series 
> models is measured from pin 1 to pin 2 of the [Series Pin Mapping] 
> entry, and currents into pin 2 would be negative. It should not be 
> necessary, but it may help to extend the table voltage range all the way 
> from -1.2V to +2.4V.
> 
>  
> 
> In my opinion it is quite likely that there could be issues with some 
> [Series Current] implementations, and the various tools may behave 
> differently. If you are an IC vendor you could submit your IBIS file to 
> the free model review service, where it will be examined and tested by 
> EDA tool vendors and other experts.
> 
>  
> 
> http://www.eigroup.org/ibis/support.htm
> 
>  
> 
> Or you could report the problem to the vendor you are using.
> 
>  
> 
> Mike
> 
>  
> 
> ------------------------------------------------------------------------
> 
> From: owner-ibis-users@server.eda.org 
> [mailto:owner-ibis-users@server.eda.org] On Behalf Of Edward Rose
> Sent: Monday, September 14, 2009 6:27 AM
> To: ibis-users@server.eda.org; ibis@server.eda.org
> Subject: [IBIS-Users] Usage of [Series Current]
> 
> Hello Experts,
> 
>  
> 
> I am trying to use [Series Current] keyword instead of [R series] in a 
> Series model as given below.
> 
>  
> 
>  
> 
> |**********************************************************************
> 
> [Model]  SER_RES
> Model_type  Series
> Polarity  Non-Inverting
> Enable  Active-High
> C_comp  0pF  0pF  0pF
> |
> |  typ  min  max
> [Voltage Range] 1.2V 1.08V 1.32V
> |
> | variable R(typ) R(min) R(max)
> |
> 
> |[R Series] 100ohm  NA  NA
> |
> [End]
> 
> |**********************************************************************
> 
> |
> [Model]  SER_CURR
> 
> Model_type  Series
> Polarity  Non-Inverting
> |Enable  Active-High
> C_comp  0pF  0pF  0pF
> |
> |  typ  min  max
> [Voltage Range] 1.2V 1.08V 1.32V
> |
> [Series Current]
> | Voltage I(typ)    I(min)    I(max)
>    0.00V   0.0A      NA  NA
>    0.10V  -1.0mA   NA  NA
>    0.20V  -2.0mA   NA  NA
>    0.30V  -3.0mA   NA  NA
>    0.40V  -4.0mA   NA  NA
>    0.50V  -5.0mA   NA  NA
>    0.60V  -6.0mA   NA  NA
>    0.70V  -7.0mA   NA  NA
>    0.80V  -8.0mA   NA  NA
>    0.90V  -9.0mA   NA  NA
>    1.00V  -10.0mA  NA  NA
>    1.10V  -11.0mA  NA  NA
>    1.20V  -12.0mA  NA  NA
> |
> [End]
> |*****************************************************
> 
>  
> 
> According to understanding from IBIS specification document,  both above 
> given models should be identical.
> 
> But, during simulation I am getting different results.
> 
> Series model with only [R series] is giving desirable result while model 
> with only [Series current] giving totally different results
> 
>  
> 
> Am I doing something wrong or there is some problem with my simulator???
> 
>  
> 
> Thanks in advance
> 
> Edward
> 
>  
> 
>  
> 
>  
> 
> 
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-- 
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 Wed Sep 23 18:09:52 2009

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