Steve, I am not comfortable with the idea of integrating around a circle. Could you describe the integration path? I expect the current will lump up in a line between the source (the capacitor) and the load (the chip). In the extreme, if the board was a mile wide, the current would not reach the edge. There is a limit where further width will not have an effect.=20 The current path will spread out, but I am unsure of how wide it is going to spread perpendicular to the path of the current. I would also expect the width of the spreading to be dependant on frequency. But there is no dependence on frequency or dielectric constant in your equation. I don't understand how that can be true. Best regards, John -----Original Message----- From: steve weir [mailto:weirsi@xxxxxxxxxx]=20 Sent: Monday, September 25, 2006 5:38 PM To: Hill, John; Sirisha.Godavarthy@xxxxxxxxxxxx; Tim.J.Nash@xxxxxxxxxxxxx; silist Subject: RE: [SI-LIST] Re: Spreading Inductance John we solve for inductance between two circular ports by performing=20 integration of the incremental field intensity using the Law of Biot=20 and Savart. That states that dB =3D uo*i/4pi * dl sin theta / r^2, magnitude only alternatively dB =3D u0i/4pi*dl x r / r^2 to obtain both direction and magnitude Integrate this formula and you get B. Since L =3D B/H, and we=20 stipulate H, this gives us L. So, back to our planes. When we look at power delivery to an IC die,=20 it is not at the end of a long skinny transmission line, it is inside=20 the extents of the planes. Current density and hence B both rise as=20 we approach the IC, and diminish as we move away. This is analagous=20 to what happens with spreading resistance. In a planar structure we=20 yield resistance per square. Best Regards, Steve. At 02:14 PM 9/25/2006, Hill, John wrote: >Steve, > >I understand that in a transmission line the inductance per unit length >and capacitance per unit length are related. As you know, the equation >is: > >The relative permeability times the relative dielectric constant divided >by the speed of light squared is equal to the inductance per unit length >times the capacitance per unit length. > >I believe we can model the power planes as a transmission line >connecting the decoupling capacitor and the load (chip). Given a BC24 >material with a Capacitance of 1 nF per inch (39 nF per meter) with a >dielectric constant of 4.5. I expect the inductance per unit length to >be 1.27 nF per meter (32.2 pH per inch) > >L=3D(4.5 * 1)/(c^2 * 39 nF per meter) > >The Zo would be 179 milliohms. Remember to terminate the transmission >line or it will show a low impedance resonance at a quarter wavelength >of electrical length. > >Now we still need to deal with the inductance of the connecting vias, >but I am planning on using an array of laser drilled micro vias. > >How did you derive the equation shown below for the L of PLANE_CAVITY? >It does not contain the things that I would be looking for in such an >equation. It looks like the equation for the inductance of a via. > >So again I ask: Why are you using Ohms per Square? > >Best regards, > >John > > > >-----Original Message----- >From: steve weir [mailto:weirsi@xxxxxxxxxx] >Sent: Monday, September 25, 2006 11:46 AM >To: Hill, John; Sirisha.Godavarthy@xxxxxxxxxxxx; >Tim.J.Nash@xxxxxxxxxxxxx; silist >Subject: RE: [SI-LIST] Re: Spreading Inductance > >John, it is just English / Metric conversion: > >1.257E-6 H/m * 0.0254 m/inch =3D 31.92 H/inch > >Best Regards, > > >Steve. >At 08:27 AM 9/25/2006, Hill, John wrote: > >Steve, > > > >I was under the impression that the Permeability of free space was 4PI > >times 10 to the -7. That is 1.257 X 10 to the -6 henrys per meter. > > > >This comes from the square of the speed of light being equal to one >over > >the permeability time the dielectric constant. The dielectric constant > >of free space being equal to 8.85 X 10 to the -12 farads per meter. > > > >Where does the per square come from? > > > >Best regards, > > > >John > > > >-----Original Message----- > >From: si-list-bounce@xxxxxxxxxxxxx >[mailto:si-list-bounce@xxxxxxxxxxxxx] > >On Behalf Of steve weir > >Sent: Monday, September 25, 2006 10:59 AM > >To: Hill, John; Sirisha.Godavarthy@xxxxxxxxxxxx; > >Tim.J.Nash@xxxxxxxxxxxxx; silist > >Subject: [SI-LIST] Re: Spreading Inductance > > > >John, this is the permeability of free space. It is an observed > >constant behavior. > > > >Best Regards, > > > > > >Steve. > >At 07:30 AM 9/25/2006, Hill, John wrote: > > >Steve, > > > > > >Where does the 31.9nH/Square come from? > > > > > >Best regards, > > > > > >John > > > > > > > > > > > > > > >--------------------------------------- > > >The information in this email and attachments hereto may contain > > >legally privileged, proprietary or confidential information that is > > >intended for a particular recipient. If you are not the intended > > >recipient(s), or the employee or agent responsible for delivery of > > >this message to the intended recipient(s), you are hereby notified > > >that any disclosure, copying, distribution, retention or use of the > > >contents of this e-mail information is prohibited and may be > > >unlawful. When addressed to Takata customers or vendors, any > > >information contained in this e-mail is subject to the terms and > > >conditions in the governing contract, if applicable. If you have > > >received this communication in error, please immediately notify us > > >by return e-mail, permanently delete any electronic copies of this > > >communication and destroy any paper copies. > > >--------------------------------------- > > >-----Original Message----- > > > > > >From: si-list-bounce@xxxxxxxxxxxxx > >[mailto:si-list-bounce@xxxxxxxxxxxxx] > > >On Behalf Of steve weir > > >Sent: Tuesday, September 19, 2006 12:28 AM > > >To: Sirisha.Godavarthy@xxxxxxxxxxxx; Tim.J.Nash@xxxxxxxxxxxxx; silist > > >Subject: [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 =3D3D u0 / 2=3DF0 * H * (( ln( R2/R1 ) * = KPERF ) + > > > >ln( R3/R2 )) > > > >- u0 =3D3D 31.9nH/square > > > >- H =3D3D cavity height > > > >- R3 =3D3D radius from die center to bypass cap ring > > > >- R2 =3D3D radius from die center to via field edge > > > >- R1 =3D3D 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. > > > >=3D20 > > > > > > > >-----Original Message----- > > > >From: si-list-bounce@xxxxxxxxxxxxx > > >[mailto:si-list-bounce@xxxxxxxxxxxxx] =3D > > > >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 = =3D > > > >dimensionless > > > >(i.e. nH/sq) and not a function of the distance between two points, >=3D > > > >rather a > > > >function of aspect ratio of the plane - L x W. So, the size of the >=3D > > > >plane > > > >isn't what affects spreading inductance, but its shape does. Are > >these > > >=3D > > > >true > > > >statements? I want to make sure I understand this correctly. > > > >Best Regards, > > > >Tim > > > > > > > > > > > >-- Binary/unsupported file stripped by Ecartis -- > > > >-- Type: application/x-pkcs7-signature > > > >-- File: smime.p7s > > > > > > > > > > > >------------------------------------------------------------------ > > > >To unsubscribe from si-list: > > > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject >field > > > > > > > >or to administer your membership from a web page, go to: > > > >//www.freelists.org/webpage/si-list > > > > > > > >For help: > > > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > > > > >List FAQ wiki page is located at: > > > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > > > > > >List technical documents are available at: > > > > http://www.si-list.org > > > > > > > >List archives are viewable at: =3D20 > > > > //www.freelists.org/archives/si-list > > > >or at our remote archives: > > > > http://groups.yahoo.com/group/si-list/messages > > > >Old (prior to June 6, 2001) list archives are viewable at: > > > > http://www.qsl.net/wb6tpu > > > > =3D20 > > > > > > > >------------------------------------------------------------------ > > > >To unsubscribe from si-list: > > > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject >field > > > > > > > >or to administer your membership from a web page, go to: > > > >//www.freelists.org/webpage/si-list > > > > > > > >For help: > > > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > > > > >List FAQ wiki page is located at: > > > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > > > > > >List technical documents are available at: > > > > http://www.si-list.org > > > > > > > >List archives are viewable at: > > > > //www.freelists.org/archives/si-list > > > >or at our remote archives: > > > > http://groups.yahoo.com/group/si-list/messages > > > >Old (prior to June 6, 2001) list archives are viewable at: > > > > http://www.qsl.net/wb6tpu > > > > > > > > > >------------------------------------------------------------------ > > >To unsubscribe from si-list: > > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > > > >or to administer your membership from a web page, go to: > > >//www.freelists.org/webpage/si-list > > > > > >For help: > > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > > >List FAQ wiki page is located at: > > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > > > >List technical documents are available at: > > > http://www.si-list.org > > > > > >List archives are viewable at: > > > //www.freelists.org/archives/si-list > > >or at our remote archives: > > > http://groups.yahoo.com/group/si-list/messages > > >Old (prior to June 6, 2001) list archives are viewable at: > > > http://www.qsl.net/wb6tpu > > > >------------------------------------------------------------------ > >To unsubscribe from si-list: > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > >or to administer your membership from a web page, go to: > >//www.freelists.org/webpage/si-list > > > >For help: > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > >List FAQ wiki page is located at: > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > >List technical documents are available at: > > http://www.si-list.org > > > >List archives are viewable at: > > //www.freelists.org/archives/si-list > >or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages > >Old (prior to June 6, 2001) list archives are viewable at: > > http://www.qsl.net/wb6tpu > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu