[SI-LIST] Re: Power delivery model with real GND ports ?

  • From: "Aubrey Sparkman" <asparky@xxxxxxxxxxxxxxxxxxxxxxxx>
  • To: "'steve weir'" <weirsi@xxxxxxxxxx>, "'Haller, Motti'" <motti.haller@xxxxxxxxx>
  • Date: Tue, 23 Nov 2010 09:52:35 -0600

Steve,

Let me ask you to reconsider based on your own comments.  IF the customer is
asking for a more accurate package model from Intel, they would probably
want all the node 0 connections to be in the PCB with Vdd and Vss
connections somewhat like a signal, because, as you said below, using a node
0 connection in the package would short out real power distribution issues.

There was some work in the mid 90s with simulation and measurement
techniques where a temporary ground was used for peripheral leaded parts
such that all pins were treated as signals which allowed a full matrix
without the use of node 0.  Look for stuff related to JEDEC JC-15.  Also,
there was some work and a paper by Bryan Young on the math to transform the
inductance matrix from one with a temporary ground to one where the matrix
was reduced by identifying specific pins as ground.  But at the time,
"single lump" models were sufficient.

I think the technique for using a temporary ground for the package is still
valid, but I haven't tested recently.  Certainly the transform math gets way
more complex when the phase difference across the package is no longer very
small at the bandwidth frequency.


Aubrey Sparkman
512-461-6165
asparky@xxxxxxxxxxxxxxxxxxxxxxxx

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of steve weir
Sent: Tuesday, November 23, 2010 8:10 AM
To: Haller, Motti
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Power delivery model with real GND ports ?

I think the problem is with your customer's concept of ground.  Your PDN is
going to exhibit voltage drops from wherever you define your reference Vdd
and Vss points.  If you attach node 0 connections in more than one place you
will in effect short out parts of your model and it will not report correct
results.

If you just want voltage measurements referenced to SPICE node 0 for
convenience, insert E elements for those measurements.

Steve


Haller, Motti wrote:
> Hi
> Does anyone know how to create a power delivery model without losing the
GND ports?
>
> My end user want to have the gnd/vss (in & out) ports not embedded as ref
but as real ports.
>
> (can be touchstone / spice or RLGC).
>
> If I use this gnd source/sync port as ref. How does the gnd resistance and
inductance reflects into the VCC* ports/nets.
>
>
> Thanks
> Motti
>
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Steve Weir
IPBLOX, LLC
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