[SI-LIST] Re: Package Model in IBIS
- From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
- To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 27 Jun 2011 18:14:21 +0000
Russell,
Reading between the lines of your question it seems that
you imply that the cancellation I mentioned "gets rid" of
some "negligible" delay. If this is what you are thinking
I have the feeling that you misunderstood what I was trying
to say.
Let me illustrate this with an example:
If you have a package model which was generated using meters
as the unit for length and has the following data:
L = 2000 nH/m
C = 3000 pF/m
Length = 0.001 meter
then the simulator will make a model which consists of
L=2nH
C=3pF
Notice that the length canceled out. However, these numbers
can still be converted to impedance (Zo) and time delay (Td)
with the usual equations (in case you wanted to model this
with a T-line), so no delays are lost...
Arpad
=============================================================
-----Original Message-----
From: Russell Dill [mailto:Russ.Dill@xxxxxxx]
Sent: Monday, June 27, 2011 11:57 AM
To: Muranyi, Arpad
Cc: si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: Package Model in IBIS
If the package is sufficiently large, it would seem like the delay
could make a difference, especially if the impedance of the package
differs greatly from the impedance of the PCB trace.
On Mon, Jun 27, 2011 at 9:09 AM, Muranyi, Arpad
<Arpad_Muranyi@xxxxxxxxxx> wrote:
> That's because the rule is to give the length
> in the same unit as the RLC per unit length.
> If you multiply these two, the length drops out,
> so for the simulator it really doesn't matter.
> Arpad
> ==================================================
>
> -----Original Message-----
> From: Russell Dill [mailto:Russ.Dill@xxxxxxx]
> Sent: Monday, June 27, 2011 11:08 AM
> To: Muranyi, Arpad
> Cc: si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Re: Package Model in IBIS
>
>> The first two methods only support RLC data, there is no
>> length in this data. The RLC matrix is also without length.
>> The only syntax that can provide length is the multi-segment
>> uncoupled syntax, but even with this one, if length is 0,
>> the tool has to implement the RLC data as a lumped model.
>>
>> I hope this helps,
>
> BTW, I noticed that the IBIS specification specifies that "Lengths are
> given in terms of arbitrary 'units'." Any clue what the logic is to
> providing a length, but not actually giving it meaning? Is it just
> save the maker of an IBIS file from multiplying LRC per unit length by
> length?
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