[SI-LIST] : Selection of Optimum Termination

Abe Riazi (ariazi@anigma.com)
Mon, 19 Oct 1998 20:58:56 -0700

Hi Everyone:

Termination constitutes an important topic of signal integrity. I
have been interested in reviewing articles which describe the required
steps for determination of optimum termination for a high speed digital
design.

Many papers written on this subject, include an excellent description
of various types of termination (i.e. Series, Parallel, Thevenin, Diode,
etc.). Some of the articles illustrate that to select the correct
termination for a high speed digital design, it is necessary to take
into consideration the technology (i.e. CMOS, TTL, ECL, etc.) of the
components. This is due to the fact that several characteristics of the
drivers and receivers (for example rise and fall times, input and output
impedances) play a critical role in determination of the optimum
termination method and component values. I was impressed by a more
recent publication which discussed another significant element, namely
the routing scheme (i.e. daisy chain, star, point to point, etc.) or
topology, which should be also carefully evaluated when choosing a
termination technique. For instance, parallel termination is well
suited for daisy chain routing, and series termination is frequently a
superior choice for the star topology.

Topology, Termination, and Technology are at times referred to as
the three "T"s of signal integrity. A careful appraisal of each of the
three is often a necessity when determining the most effective
termination type.

I would appreciate your comments and suggestions related to required
considerations, computations, or steps towards selection of optimum
termination.

Best Regards,

Abe Riazi
SI Engineer
Anigma, Inc.

email: ariazi@anigma.com

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