Re: [SI-LIST] : Daisy Chain topology - termination schemes

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From: Nianci Wang (nwang@amcc.com)
Date: Fri May 11 2001 - 08:38:35 PDT


Hi Selva,

The main reason for daisy chain topology showing non-monotoniciry on
the edges of the data is the multi-reflection on the main chain due to
mismatch. The first load have the most reflection, therefore show worst
affected.

One thing you can try is to find out how much equivalent capacitance
seeing from the main chain to each load and count this capacitance
as part of your transmission line capacitance. In other word, just see
your transmission line alone, it is not 50 ohm trace, usually have a
higher characteristic impedance, when you count the capacitance
contribution, it is a 50 ohm transmission line. In this way you can
reduce most of the reflection. This is a common technique to design
distributed amplifier. You can check some microwave book for the
concept.

Best Regards
Nianci

selvaraj subramanian wrote:

> Hello all, My simulations using XTK for most of the daisy chain
> topology is showing non-monotonicity on both the edges of the
> data/signal. I tried different termination strategies to remove the
> kink. But couln't. What I saw was that the worst affected load is the
> first load from the driver? Suggest me how to remove the
> non-monotonicity while using the daisy chain topology and is it ok if
> I bring that kink within the threshold levels. thanks in
> advance. regards,Selva

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