From: Larry Miller ([email protected])
Date: Mon Feb 26 2001 - 20:10:31 PST
---which brings up something that has been bothering me:
the LVDS standard goes with the single 100-ohm line-to-line resistor (which
is REQUIRED for DC biasing) but does not seem to provide any specific line
to ground termination. I know that LVDS was originally intended for cables,
but it is showing up in a lot of 2-3 Gb signals, including serial
backplanes.
It looks to me as though you end up with unterminated (to ground) wires in
the pairs.
What do you do with this?
Seriously.
Larry Miller
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Eric Goodill
Sent: Monday, February 26, 2001 6:09 PM
To: [email protected]
Subject: Re: [SI-LIST] : Combined single-ended/differential termination
package?
Ron,
Our reason for both resistors is to terminate any common-mode signal
that might be on the lines either from crosstalk or from an unbalanced
driver.
-Eric
Ron Miller wrote:
>
> Hi Eric
>
> Why not just use a single resistor to terminate the differential mode,
> which is the signal you are intrested in.
>
> Tieing the center-tap to ground allows common mode currents to flow
> which usually end up allowing power supply ground currents to get into
> the sensitive signal paths.
>
> -----Original Message-----
> From: Eric Goodill [mailto:[email protected]]
> Sent: Monday, February 26, 2001 3:47 PM
> Subject: [SI-LIST] : Combined single-ended/differential termination
> package?
>
> Hi,
>
> We often use this termination scheme:
>
> SIG+ -------+
> |
> R
> |
> +--C--+
> | |
> R V
> | GND
> SIG- -------+
>
> That is, two resistors in series between the differential signals with a
> center-tapped capacitor to ground. Is there a combined device to sucks
> all these parts into a three-pin package?
>
> Regards, Eric
-- Eric Goodill Redback Networks [email protected] 300 Holger Way voice: (408) 571-5319 San Jose, CA 95134-1362**** To unsubscribe from si-list or si-list-digest: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu ****
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