Re: [SI-LIST] : Physcially-small far-end LVDS terminations?

About this list Date view Thread view Subject view Author view

From: Milt Schwartz x3261 ([email protected])
Date: Mon Dec 20 1999 - 12:34:07 PST

I agree Jon.
The LVDS devices require a termination resistor. If compliant with TIA/EIA 644, then the resistor value that will be supported by the specified output voltage swing is 90 to 120 ohms (if I remember the spec correctly).

> From [email protected] Sat Dec 18 12:48:42 1999
> Date: Sat, 18 Dec 1999 09:08:31 -0800
> From: Jon Powell <[email protected]>
> Subject: Re: [SI-LIST] : Physcially-small far-end LVDS terminations?
> To: [email protected]
> MIME-version: 1.0
> X-Mailer: Mozilla 4.05 [en]C-PBI-NC404 (Win95; U)
> Content-transfer-encoding: 7bit
> Sender: [email protected]
> Reply-To: [email protected]
>
> Though I could easily be wrong, I don't believe that the below is true. My understanding of LVDS is that it requires ~100 ohm termination across the differential receiver in order to generate the required signal voltage.
>
> regards,
> jon
>
>
> Jim Freeman wrote:
>
> > Hi Eric,
> > Another answer would be to ensure that the differential impedance of the board between the differential pairs is 100 ohms. Then you wouldn't need the resistors. I have performed Hspice sims on this and it works fine if the stackup/trace spacing is correct.
> >
> > Jim Freeman
> >
> > Eric Goodill wrote:
> >
> > > Hi,
> > >
> > > I want to use the typical LVDS termination where you have two 50-ohm resistors in series placed between the two lines of the LVDS diff. pair and also have a cap at the junction of the resistors to ground. I have a jillion LVDS pairs to terminate at a high-pin-count ASIC, and I'm looking to squeeze more terminations per square inch. (There's no hope of putting the terminations inside the ASIC at this point.) I'm hoping some company makes a single three-pin part the has those two resistors and a cap even if not specifically for termination use.
> > >
> > > How about any other ideas for even higher density?
> > >
> > > Regards, Eric
> > > --
> > > Eric Goodill
> > > Siara Systems, [email protected]
> > >
> > > **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
> > > si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list
> > > ****
> >
> > **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
> > si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list
> > ****
>
>
>
> --
> Jon Powell
> Director of HSSD Consulting Services
> Viewlogic Systems, INC.
> 805 988 8250
>
>
>
> **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list
> ****
>
>

**** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list
****

About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Tue Feb 29 2000 - 11:39:09 PST