FreeLists / si-list / [SI-LIST] Re: How to calculate the resistance and inductance of vias

[nsi041350-Roberts <jgroberts@xxxxxxxxxx>]

Hi  Zhangkun,
        Sorry for the late reply.
        All formulae are based on approx to one degree or another.
What I think is more important is to consider the effects in your particular
application.
If you consider it for power connections where there are high current and low
impedance
you would concentarte on the inductance and resistance parameters.
However, for transmission you should not neglect the effects of capacitance and
stub length.
If of interest i have a presentation of some these effects and "approximations".

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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.



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