Re: About WARNING of ibischk2

Akihiro,

I'm not sure I understand your question exactly.

The slope of the load line designated by "x"'s in your diagram is just
the load resistance 50 Ohms (= 50 Volts/Amp). Its actually -50 due to
the current polarity.

The load-line represents the load resistor while the V/I curve
designated by "*" in your diagram represents the DC characteristics of
the totem pole output stage while driving low (top transistor off) shown
in Fig 2.

Hope this answers your question.

Chris

Akihiro Takegama wrote:
>
> Chris,
> I'm sorry. I would like to cofirm my opinion, and I have one question.
>
> [1] Is slope of V(R) of <Fig 1> based on V(R) of <Fig 2>, isn't it ?
>
> <Fig 1> <Fig 2>
> [Pulldown] + [GNDclamp] --- Vcc ---
> (I) or [POWERclamp] ^ ^
> | * | | |
> 0.6A x **** | | |
> | x ** |-+ | I | V (Pch)
> | x * +--o|| | |
> | * | |-+ +------+ |
> | * ^ x L | | | V
> | * | x slope = -50 Ohm --+ +------+ | ----
> | * | x | | | V ^
> *--------|-----------x--------- | |-+ < |
> 0.0V | 3.3 (V) +---|| < 50 | V (R)
> (V_fixture) |-+ < Ohm |
> |<------>|<--------->| | | V
> V(Pch) V (R) --- --- ---
> /// /// ///
>
> [2] Could you tell me the reason why it is 2% ?
> Is this must value ?
> ( You decided the value on Oct. in 1996. )
> If we decided the diode value, the value is lower the IV curve (leak).
>
> We have the IBIS check problem yet. The last warning disappeared by your
> cooperation.
> The max voltage value can't be up 2.81V. ( Below is in 3% margin )
> ----------------------------------------------------------------------------
> WARNING - Model 'inout': MAX AC Falling Endpoints (-0.00V, 2.73V) not within
> 0.055V (2%) of ( 0.00V, 2.81V) on VI curves for 50 Ohms to 0V
> ----------------------------------------------------------------------------
>
> - Regards,
> A.Takegama ( tkgm@tdc.tijp.ti.com )
>
> ************************************
> * Name : Akihiro Takegama *
> * E-mail : tkgm@tdc.tijp.ti.com *
> * Corp. : Texas Instruments *
> ************************************
> - -----------------------------------------------------------------------
>
> - ------- Start of forwarded message -------
> Sender: crokusek@qdt.com
> Date: Wed, 01 Apr 1998 09:21:51 -0800
> From: Chris Rokusek <crokusek@qdt.com>
> Organization: Quad Design Technology
> X-Mailer: Mozilla 3.01 (X11; I; SunOS 4.1.4 sun4m)
> Mime-Version: 1.0
> To: Akihiro Takegama <tkgm@mario.tdc.tijp.ti.com>
> Cc: ibis-users@vhdl.org
> Subject: Re: [Re: About WARNING of ibischk2]
> References: <199804010915.SAA15589@mario.tdc.tijp.ti.com>
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
>
> Akihiro,
>
> The "LOW" curve used in the DC vs. AC test is the sum of BOTH shunt
> curves (POWER_Clamp/GND_Clamp) + the Pulldown Curve.
>
> Similarly the "HIGH" curve used in the test is the sum of BOTH shunt
> curves + Pullup Curve.
>
> Chris
>
> Akihiro Takegama wrote:
> >
> > Chris,
> > thank you very much for your quick response and answer.
> >
> > I would like to confirm my issue.
> >
> > # Is it crosspoint 50 Ohm slope against the value of [Pulldown]
> > + [Gndclamp] ?
> >
> >
> > (I)
> > | * [Pulldown] + [GNDclamp]
> > 0.6A x ****
> > | x **
> > | x *
> > | *
> > | * ^ x
> > | * | x slope = 50 Ohm
> > | * | x
> > *--------|-----------x---------
> > 0.0V | 3.0 V (V)
> > (0.95V)
> > #####
> >
> > - Regards,
> > A.Takegma
> > > ************************************
> > > * Name : Akihiro Takegama *
> > > * E-mail : tkgm@tdc.tijp.ti.com *
> > > * Corp. : Texas Instruments *
> > > ************************************
> >
> > -----------------------------------------------------------------------
> > ------- Start of forwarded message -------
> > Sender: crokusek@qdt.com
> > Date: Tue, 31 Mar 1998 10:01:46 -0800
> > From: Chris Rokusek <crokusek@qdt.com>
> > Organization: Quad Design Technology
> > X-Mailer: Mozilla 3.01 (X11; I; SunOS 4.1.4 sun4m)
> > Mime-Version: 1.0
> > To: Akihiro Takegama <tkgm@mario.tdc.tijp.ti.com>
> > Cc: ibis-users@vhdl.org
> > Subject: Re: About WARNING of ibischk2
> > References: <199803311308.WAA12838@mario.tdc.tijp.ti.com>
> > Content-Type: text/plain; charset=us-ascii
> > Content-Transfer-Encoding: 7bit
> >
> > Akihiro,
> >
> > The ibishk2 program is checking the first and last point of your Rising
> > and Falling AC Waveforms against the DC VI curves and given test load
> > (50 Ohms).
> >
> > For your case the message indicates that the first point given in the
> > Rising Waveform table is .74V.
> >
> > If you were to plot the intersection of a 50 Ohm to 3V load line (slope
> > = 50 V/I) and the given DC VI curve you would see that they interesect
> > at .95V (this is fist value in [3] below).
> >
> > So since
> >
> > abs(.95 - .74) > 2% * (3 - .74)
> > .21 > .045
> >
> > The checker will print a warning.
> >
> > The reason for the check is that the first and last points of the AC
> > waveforms are supposed to be the stable DC value when driving the given
> > load.
> >
> > Chris Rokusek
> > Viewlogic
> >
> > Akihiro Takegama wrote:
> > >
> > > To: IBIS-users,
> > >
> > > Hello, I'm making the IBIS model. But I am confused at ibischk.
> > > Could you support me ?
> > >
> > > I have one question.
> > >
> > > 1 ) I made the IBIS model within "Rising Waveform" and "Falling
> > > Waveform" and I ran the ibischk2. But many warning appeares
> > > it's IBIS model, which like as below.
> > > Could you please tell me how to calculate the value [3]. ?
> > >
> > > - ----------------------------------------------------------------------------
> > > WARNING - Model 'inout': MIN AC Rising Endpoints ( 0.74V, 3.00V) not within
> > > -------------
> > > [1]
> > >
> > > 0.045V (2%) of ( 0.95V, 3.00V) on VI curves for 50 Ohms to 3V
> > > ----------- ----------------
> > > [2] [3]
> > > - -----------------------------------------------------------------------------
> > >
> > > - Regards,
> > > A.Takegama
> > >
> > > ************************************
> > > * Name : Akihiro Takegama *
> > > * E-mail : tkgm@tdc.tijp.ti.com *
> > > * Corp. : Texas Instruments *
> > > ************************************
> > > ------- End of forwarded message -------
Received on Mon Apr 6 11:05:48 1998