[SI-LIST] Re: SSN analysis?

  • From: "Peterson, James F \(EHCOE\)" <james.f.peterson@xxxxxxxxxxxxx>
  • To: <fasig.jonathan@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 3 Aug 2006 11:17:10 -0500

 hello Jonathan -=20

Do you want to estimate the amount of current rushing in or out of the
Altera part, or do you want to analyze the impact of this current surge?

If it's the amount of I, then it is straight forward - but don't use the
old "hang a capacitor on the buffer" approach. Think transmission line
and represent the t-line with a resistor equal to Zo and another
resistor for Zs (source impedance) and then tie them to rails (note :
there might be other resistors in the path depending on your HSTL term
scheme). Solving for I (E/Rtotal) seems to line up very well with SI
simulators that can measure the in-rush current (if you have one you can
just simulate to get the answer). then take this answer and multiply
times the # of outputs switching at the same time for total surge
current.

If it's the second question (what does this current surge do to my
Altera's internal PDS?), then I can't help as much (sorry). There is a
technique that's sometimes called the "portal method", that is used to
look inside the device. Attach a scope to a quiet buffer driving high.
Switch all the outputs from a 0 to a 1 and note the noise spike on the
scope (the buffer is driving 1 so you are looking at the Vdd rail). Then
have the quiet buffer drive a logic 0 (Vss rail) and switch all of the
outputs from a logic 1 to 0 and note the noise spike. I've used this
method on large devices and it seems to work ok, but it needs a fast
scope.=20

The missing part of this is when will the part fail. This is usually
defined as when a quiet buffer toggles because of all the noise...I'd
try to get Altera to help you with this.

Hope this helps.

Jim
Honeywell

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Fasig, Jonathan L.
Sent: Thursday, August 03, 2006 9:45 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] SSN analysis?

We are working on SSN analysis for an application that will have 600
HSTL I/O's on an Altera Stratix-II GX130.  Is there anyone in this
community who has done (or is currently doing) similar work?

jf

-------------------------------------------------------------------

Jonathan Fasig                      Email:  fasig.jonathan@xxxxxxxx=09
Mayo Foundation
4001 41st Street NW=20
MSC Sn 2-132                        Phone:  (507) 538-5464
Rochester, MN 55901                 Fax:    (507) 284-9171
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