Re: Termination Resistor - RS-485 line.

On Tue, 03 Apr 2007 21:30:05 +0200, Rene Tschaggelar <none@xxxxxxxx>
wrote:

John Larkin wrote:

On 3 Apr 2007 12:12:51 -0700, "Franco" <rmendoza79@xxxxxxxxx> wrote:


Hey guys, fast question: Is it possible to use as a termination
resistor (in a RS-485 bus) a combination of L and C in series instead?

I am just trying to find a way to set a termination resistor that does
not imply such a big load as a pure 120ohm resistor.

Cheers...

Franco.


Sounds bad to me. If the data rate is low, just don't terminate it, or
use a series R-C. At high rates (relative to line length) any
non-resistive termination can cause pattern-dependent distortion,
"deterministic jitter" and possible errors.


John,
the idea of the poster was AC termination. Meaning a 100
Ohms in series with perhaps a 100nF.

Rene


I mentioned series R-C termination. Again, that can cause
pattern-dependent timing errors and may snarf the data. If the data
has no DC or low-frequency components (like NRZI or Manchester), the
series R-C will work, but saves no power!

John

.

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