Just a few comments to the answer from Thomas.
1) The impedance matrix is a complete description of unterminated multiport
system. It is so called open-circuit matrix that is obtained with the
following experiment. We apply unit current source to one of the ports and
measure voltage responses at this and all other ports, that are
open-circuited (unterminated). The voltage at the port with the source is
the self-impedance and the voltages at the other ports are the off-diagonal
elements of the impedance matrix or trans-impedances. They can be used to
compare qualitatively PDN configurations - zero trans-impedance, for
instance, means ideal isolation of two power delivery systems (more relevant
for EMC/EMI). System with lower trans-impedances will have better isolation
of the components - though, even in this case properly terminated
S-parameters would be preferable. Also, to evaluate the impedance at the
component location or possible supply voltage variations, we need to
terminate all ports of the multiport (by normalization or reduction of all
ports to one). The trans-impedances are always in the mix as parts of the
diagonal impedance matrix elements. To understand it better, you may need to
read some introductory books on theory of multiports and PDN
characterization.
2) Both may be misleading, because of absence of port terminations.
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
2629 Townsgate Rd., Suite #235, Westlake Village, CA 91361, USA
Office +1-702-876-2882; Fax +1-702-482-7903
Cell +1-206-409-2368; Virtual +1-408-627-7706
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Simbeor - Accurate, Productive and Cost-Effective Electromagnetic Signal
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Thomas Beneken
Sent: Wednesday, October 12, 2016 3:23 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: PDN simulation - Trans-impedance versus
self-impedance
Hi Liviu-Dumitru,
1) a variation of current into pin 9 translates with a factor of Z[2,9] into
a voltage ripple on pin 2
2) the voltage ripple on a pin adds up from self produced current variations
(self impedance) AND current variations on other pins of the PDN (transfer
impedance). So the answer is self and transfer impedances are significant.
Hope this helps.
Thomas
Am 12.10.2016 um 11:37 schrieb Craciun, Liviu-Dumitru:
Hi all,course, in the "real world" there are more IC power pins.
for the PDN simulation I placed the Port[1] at the output pin of the
VRM (voltage regulator module) and the Port[2], Port[3], ... Port[11]
at the IC power pins.
The PDN with only 10 IC power pins is only a simplified example, of
the VRM and each IC power pin.
The power integrity simulation software is able to calculate the
self-impedances Z[1,1] at the VRM and Z[2,2], ... Z[11,11] at the IC.
There are the diagonal elements of the impedance matrix.
The elements Z[1,2], Z[1,3], ... Z[1,11] are the trans-impedances between
"trans"-impedance.
In generally, the PDN requirements in the IC data sheet contain only
ONE parameter - Z value @ Freq. - without to specification "self"- or
two IC power pins ? For example Z[2,9]
MY QUESTIONS:
1) What is the physical significance of the trans-impedance between
mean, self- or trans-impedance?" The standard answer is "only the
2) The IC provider can `t answer the question "what impedance do you
Best regards,
Liviu Craciun
Harman Becker Automotive Systems GmbH
Karlsbad, Germany
P.S.
I expected from the IC provider TWO impedances as specifications,
self- and trans-impedance, But I received ONLY ONE value. It is
unknown if the spec means the self- or the trans-impedance.
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