[SI-LIST] Re: differential signaling terminator.
- From: "Tom Dagostino" <tom@xxxxxxxxxxxxx>
- To: <jtalavera@xxxxxx>, "'si list'" <si-list@xxxxxxxxxxxxx>
- Date: Sat, 16 Nov 2002 15:11:08 -0800
You cannot terminate an ECL differential line with a single resistor. ECL
needs a pull down resistor to Vcc - 2 Volts to keep the output devices
biased. A single resistor tied between the two outputs will not give the
proper load (bias condition). AC termination also does not work for ECL for
the same reason, you need a DC path to keep the output devices active.
LVDS will accept a differential termination.
Tom Dagostino
Device Modeling Division
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 430-1065
tom@xxxxxxxxxxxxx
http://www.teraspeed.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Juan Manuel
Sent: Saturday, November 16, 2002 6:33 AM
To: si list
Subject: [SI-LIST] differential signaling terminator.
Hello everybody,
I write you because I would like to know what is the best technique to
terminate differential signaling today for LVDS and ECL.
I know there is a classic thechnique of put a resistor between tx lines with
the differential impedance value ( 2*intrinsic impedance ) to terminate the
differential-mode signal. I also know that the thevenin or AC termiantion
can be used to terminate the diffential-mode and common mode signal.
I read a lot of information about that but, is the single resitor technique
falling into disuse due to it is useless for common mode signal termination?
I ask this because ECL manufacturers do not say anything in their
application notes about single resistor technique.
Thank you. Beforehand.
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