Re: [SI-LIST] : Return path for stripline, two ground planes or one power and one ground?

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From: Vinu Arumugham (vinu@cisco.com)
Date: Tue Apr 04 2000 - 17:10:38 PDT


To make PECL differential signal lines wider while keeping the board thickness down, they have to be loosely coupled. The reference plane is therefore the primary return path.

Vinu

Chris Cheng wrote:

> actually, most of the current pecl designs are differential in which the
> switching
> current returns through the complimentary side. the differential part
> doesn't really
> need a fixed reference plane. the common mode part will suffer from plane
> discontinuity.
> chris
> -----Original Message-----
> From: Vinu Arumugham [mailto:vinu@cisco.com]
> Sent: Tuesday, April 04, 2000 11:57 AM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : Return path for stripline, two ground planes or
> one power and one ground?
>
> "Ingraham, Andrew" wrote:
>
> >
> >
> > If the driver is PECL, then ~all the switching current goes through the
> IC's
> > power (+Vcc) pins and ~none through the ground (-Vee) pins. In that case,
> > stripline between two power planes would be best. (Or with normal ECL,
> use
> > stripline between two ground planes. That's why ECL used a negative
> > supply!)
> >
>
> But PECL is usually implemented with pull down resistors to GND at the
> source. It seems to me then that there will be no difference whether the
> stripline is implemented between GND planes, power planes
> or one of each.
>
> Vinu
>
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