# [SI-LIST] Re: How to calculate the resistance and inductance of vias

*From*: "Rich Peyton" <p2rich@xxxxxxxxxxxxx>*To*: <si-list@xxxxxxxxxxxxx>*Date*: Mon, 6 Jan 2003 09:47:49 -0500

I believe it would be "partial Inductance" of the wire, where you are only looking at one particular area for understanding of changes made. In reality that would not be the true self Inductance because you do need a return path, which affects the value of self inductance other active conductor paths will affect the self inductance of original also? * Digital Signal Integrity by Brian Young, pg. 211 - "wires do not have inductance --- closed loops have inductance." * What Really is Inductance by Eric Bogatin - Good reading, I got out of PCB Design Mag/ March 2000, you may be able to download from Gigatest.com. I'd also like to hear others comments on Greg's reply! Rich -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Gregory R Edlund Sent: Monday, January 06, 2003 8:52 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] How to calculate the resistance and inductance of vias Zhangkun, I have seen forumulas similar to the ones you quoted and have always wondered how they were derived. They give answers that are in the ballpark, but do they really calculate inductance? My electromagnetics textbook, "Introduction to Electrodynamics," by David Griffiths, defines inductance as a property of current LOOPS (page 263). Self inductance is the constant of proportionality between the magnetic flux through the loop and the current. Since you can't have magnetic flux (integral of B-dot-da) unless you have a loop, can anyone on the list explain how you can define the inductance of an isolated cylindrical conductor with no return path? What assumptions does one have to make? Greg Edlund Senior Engineer Signal Integrity IBM Engineering and Technology Services 3605 Hwy. 52 N, Dept. HDC Rochester, MN 55901 gedlund@xxxxxxxxxx Msg: #1 in digest Date: Mon, 06 Jan 2003 10:24:26 +0800 From: Zhangkun <zhang_kun@xxxxxxxxxx> Subject: [SI-LIST] How to calculate the resistance and inductance of vias Hi all: Could anyone tell me how to calculate the resistance and inductance of vias. The frequancy range is from DC to 50MHz. I have seen two formulars to calculate the inductance of vias. They are very differenct. One is from High Speed Digital Design written by Howard Johnson: L=5.08*h*(ln(4h/d)+1) L:inductance of via, nH h:length of via, inch d:diameter of via, inch The other is from one paper written by Mark Alexander: L=5.08*h*(ln(4h/d)-0.75) L:inductance of via, nH h:length of via, inch d:diameter of via, inch These two formular are different. Best Regards Zhangkun 2003.01.06 ------------------------------------------------------------------ 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: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: http://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: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: http://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

**References**:**[SI-LIST] How to calculate the resistance and inductance of vias***From:*Gregory R Edlund

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