[SI-LIST] Re: Spreading Inductance

Tim, those equations come from a presentation I made to the SCVEMC 
January 2005.  You can find the presentation in whole on both the 
X2Y, and Teraspeed web 
sites:  http://www.x2y.com/bypass/method/does_position_matter.pdf, 
and http://www.teraspeed.com/publications.html  Note that they apply 
for specific circumstances of calculating spreading inductance 
between a power ring, and a surrounding bypass capacitor ring.  This 
would also work for a single Vdd / Vss pair.  However for more 
complex pin arrays, you really need to solve the plane.  Tools from 
IBM, KAW, Ansoft, or Sigrity are all capable of that task.

Steve.
At 05:57 AM 9/18/2006, Sirisha Godavarthy wrote:
>Hi Tim,
>I got some info regarding spreading inductance.
>Hope it helps.
>
>Plane spreading inductance:
>
>- L of PLANE_CAVITY =3D u0 / 2=F0 * H * (( ln( R2/R1 ) * KPERF ) +
>ln( R3/R2 ))
>- u0 =3D 31.9nH/square
>- H =3D cavity height
>- R3 =3D radius from die center to bypass cap ring
>- R2 =3D radius from die center to via field edge
>- R1 =3D radius from die center to pkg power / ground attachments.
>- KPERF scaling factor for perforation in via field
>* For perforations small compared to wavelength area ratio
>
>Thanks&Regards,
>Sirisha.
>
>Thanks&Regards,
>Sirisha.
>=20
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
>On Behalf Of Nash, Tim J (EHCOE)
>Sent: Friday, September 15, 2006 7:56 PM
>To: silist
>Subject: [SI-LIST] Spreading Inductance
>
> From what I have gathered, spreading inductance of a plane is =
>dimensionless
>(i.e. nH/sq) and not a function of the distance between two points, =
>rather a
>function of aspect ratio of the plane - L x W.  So, the size of the =
>plane
>isn't what affects spreading inductance, but its shape does.  Are these =
>true
>statements?  I want to make sure I understand this correctly.
>Best Regards,
>Tim
>
>
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