[SI-LIST] Re: Cin in IBIS models
- From: "Perry Qu" <perry.qu@xxxxxxxxxxx>
- To: arpad.muranyi@xxxxxxxxx, Andrew.Ingraham@xxxxxxxxxx
- Date: Mon, 17 Dec 2001 17:25:47 -0500
Arpad, Andy:
Thank you both for your comments. From my own understanding, IBIS
specification assumed that the IBIS model is consisted of:
I/O buffer characteristics + packaging RLC
However, it just occured to me through the special case I mentioned before,
that on-chip parasitics could be comparable to on-package parasitics (in my
case, on-chip R and C are quite big for certain pins and L is indeed small);
From timing point of view, these on-chip R and C may cause addtional delays
to the signals and should be taken into account. If as suggested by Andy/Arpad
that R is already taken into account in V/I, V/t curve and C_comp included the
on-chip interconnect C, then I guess we are still ok for the speed of signal
we are looking into.
Regards
Perry
"Muranyi, Arpad" wrote:
> The current IBIS specification does not allow anything
> for the die other than C_comp.
>
> Even though I am not the most experienced in this area,
> I haven't seen a case where the on die inductance between
> the I/O buffer and its pad was larger then the package
> inductance. Judging by the dimensions, I would think that
> it should be much smaller, and therefore negligible.
>
> However, you can brake up your problem at a different
> boundary, if you still need to do this. You could consider
> the on die interconnect being part of your package and
> include its parasitics in the package model. That way
> the C_comp will only represent the buffer capacitance alone.
> There is nothing illegal about doing this, you may just
> want to write a bunch of comments to tell the IBIS model's
> user about what you did.
>
> Arpad
> ==========================================================
>
> -----Original Message-----
> From: Khederian, Bob [mailto:RKhederian@xxxxxxxxxxxx]
> Sent: Monday, December 17, 2001 11:57 AM
> To: 'perry.qu@xxxxxxxxxxx'; arpad.muranyi@xxxxxxxxx
> Cc: si_list
> Subject: RE: [SI-LIST] Re: Cin in IBIS models
>
> The IBIS V2.1 Specification says "C_comp defines the silicon die
> capacitance. This value should not include capacitance of the package."
>
> -----Original Message-----
> From: Perry Qu [mailto:perry.qu@xxxxxxxxxxx]
> Sent: Monday, December 17, 2001 2:29 PM
> To: arpad.muranyi@xxxxxxxxx
> Cc: si_list
> Subject: [SI-LIST] Re: Cin in IBIS models
>
> Hi!
>
> Related to this question, is it good enough to represent the on-chip
> parasitics with just a C_comp ? How about R and L ?
>
> I had a case with one vendor about their receiver model: for some of the
> pins, the on-chip parasitics are even bigger compared with packaging RLCs.
> I was told that these on-chip parastics represent routing parasitics from
> C4 pads to the actual receiver; Wondering how IBIS model take these into
> account ?
>
> Thanks
>
> Perry
>
> "Muranyi, Arpad" wrote:
>
> > Bob,
> >
> > The C_comp capacitance must represent what you see when you look into
> > the die at the die pad. This includes the die pad, metal connections
> > on the die, the driver transistor's capacitance, the receiver (input)
> > capacitance, everything that is on the die. Package, pin, ball, and
> > other stuff is modeled in the package model section of the IBIS model.
> >
> > Arpad Muranyi
> > Intel Corporation
> > ======================================================================
> >
> > -----Original Message-----
> > From: Bob Patel [mailto:whizplayer@xxxxxxxxx]
> > Sent: Monday, December 17, 2001 10:27 AM
> > To: si_list
> > Subject: [SI-LIST] Cin in IBIS models
> >
> > Hi! Is the input capacitance for a pin included in the
> > IBIS models, I know the pad capacitance is by using
> > C_comp. Also, when using output buffers do I have to
> > model the output capacitance as an external capacitor
> > and the input capacitance as an external capacitor.
> > Thanks in advance
> > Bob
> >
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> --
> Perry Qu
>
> Product Integrity | 600 March Road
> Alcatel Canada | Ottawa, ON K2K 2E6, Canada
>
> DID: (613) 7846720 | FAX: (613) 5993642
>
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--
Perry Qu
Product Integrity | 600 March Road
Alcatel Canada | Ottawa, ON K2K 2E6, Canada
DID: (613) 7846720 | FAX: (613) 5993642
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