AW: [SI-LIST] : connector substitution for high speed signals

Wallenhorst, Ulrich ([email protected])
Tue, 8 Jun 1999 06:58:11 +0100

The question is too general to give a sufficient answer. However, I =
recommend to use (SPICE-) simulation models for comparisons if possible
instead of measurements, because You reduce the number of uncertainties =
Your assumptions (e.g. what about plated through holes, microvias, =
to the instruments, calibration technique, unequal pcb-losses,
multiline-testing ...). We spend a lot of time and efforts in =
comparison of
connectors as far as measurements (TDR/TDT, S-parameter) and =
simulations are
concerned. Surf below mentioned web-pages. (Under company profile =3D> =
laboratory =3D> publications and activities it is shown how generalized
multiline-models of connectors can be produced.)

Nevertheless, here are some general statements:

1) Contact-pitch is not a qualifying/disqualifying argument, but
signal-to-ground ratio is
2) The connector ALWAYS forms a "parallel transmission path" together =
plated through holes or microvias. This makes the story complicate =
it is ALWAYS pcb-specific if You "de-embed" the real DUT.
3) The most complex simulation-task is building crosstalk-models of
connectors because You need EM-tools (field solvers) to gain the basis =
the later performed SPICE-simulations. In many cases it is not =
sufficient to
use measurement-data to gain multiline-models because it is not correct =
use e.g. only one pi- or T-circuit element.=20
For high accuracy a (measurement-based) parameter-extraction algorithm =
simultaneously works in the time and frequency domain should be used to =
the necessary circuit-diagram.
4) It is application-dependend whether a connector is suited or not. =
strong shielded pseudo-coax pin-arrangements in multipin connectors =
in very good x-talk features but increases the slot-capacitances in =
bus-applications like cPCI or VME resulting in lower impedances of the
transmission-structure and higher prop.-delay.

Best regards

> Ulrich Wallenhorst
> Dept.: Central laboratory
> E-Mail: [email protected]
> Phone: +49 57 72 47-294
> Fax.: +49 57 72 47-403
> ----------
> Von: [email protected][SMTP:[email protected]]
> Antwort an: [email protected]
> Gesendet: Montag, 7. Juni 1999 04:15
> An: [email protected]
> Betreff: [SI-LIST] : connector substitution for high speed signals
> Hi All SI Experts,=20
> One question.=20
> If I want to use one connector to replace another connector because =
> cost issue, what criteria are needed to prove they are electrically
> equivalent.=20
> Especially the substitution is happened for high speed / low swing
> signals, such as RAMBUS signals, which have 200ps for rising time.
> Any comments or suggestions are appreciated.=20
> Thank you for helps in advance.=20
> =A0=20
> John Lin=20
> Quanta Computer Inc.=20
> CAE Engineer=20
> Tel: 1+886+03+3979000 ext. 5183=20
> Fax: 1+886+03+3975000=20
> Email: [email protected]=20

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