[SI-LIST] [Fwd: Re: Re: AC coupling placement]

From: "Hassan O. Ali" <hassan@xxxxxxxx>
To: si-list@xxxxxxxxxxxxx
Date: Thu, 31 Jan 2002 14:47:25 -0500


Placing the cap close to the receiver is the "usual" thing, but
functionally it can be placed anywhere along the path. In fact if you
just design a TX card and there is a possibility that the card can be
terminated without a DC-blocking cap by one "unscrupulous" designer (for
example, connected directly to an oscilloscope), then I'd advise to
place the cap on the TX card i.e. closer to the driver.

Regards.

Hassan.


Vinu Arumugham wrote:
> 
> Usually the AC coupling capacitor would need a couple of vias to connect
> to the lines. Reflections from this structure can be lowered by placing
> it near the receiver where the edge rate is slower than at the
> transmitter.
> 
> If you do not have very long run lengths (>100 bits), a 0.01uF will
> work.
> 
> Thanks,
> Vinu
> 
> Ben Rothchild wrote:
> 
> > Hello Experts,
> >
> > I have a question on AC coupling.
> > While AC coupling a high speed serial
> > link to match levels, where should
> > the AC coupling capacitor be placed.
> > Close to transmitter/close to receiver/
> > or doesn't matter, can be placed
> > anywhere on the link.
> >
> > What should be the value of the AC
> > coupling capacitor or rather how
> > do I calculate it. Is it dependent on
> > frequency. I am trying to AC couple
> > signals of 155M, 622M, 1.25G and 2.5G.
> > Any special care to be taken at these
> > different frequencies.
> >
> > Thanks for any advice.
> > Ben
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[SI-LIST] [Fwd: Re: Re: AC coupling placement]

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