For more information you can also refer to the Application note below:
http://support.cadence.com/wps/mypoc/cos?uriÞeplinkmin:DocumentViewer;src=wp;q=ApplicationNotes/Silicon-Package-Board_Co-Design/AC_CouplingCap_SystemSI.pdf
Best Regards,
Shiva
On Wed, May 13, 2015 at 8:35 PM, CHASTANG Cyril <
cyril.chastang@xxxxxxxxxxxxxxx> wrote:
Scott,
I agree, it is a common rule. It depends on how big the impedance mismatch
is (size of the footprint, number of vias, length of the via stubs, ...)
and the ratio between the data rate and the edge rate. The impact on the
eye diagram could be negligible.
Best regards,
Cyril
De : Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]
Envoyé : mercredi 13 mai 2015 16:51
à : CHASTANG Cyril
Cc : hanmoggq@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Objet : Re: [SI-LIST] Re: AW: AC coupling capacitor
Cyril
It is an oft repeated myth that a DC blocking capacitor should be placed
near the receiver because of signal edge rate.
A serdes channel is a linear LTI system. Where the capacitor is placed in
the channel with respect to the driver does not matter. What does matter
is how well the capacitor transition is designed, how low a reflectivity it
is, and whether it is placed near other channel discontinuities.
Regards
Scott
[http://teraspeed.com/images/logo-02.png]
Scott McMorrow
Consultant - R&D
Teraspeed Consulting - A Division of Samtec
16 Stormy Brook Rd
Falmouth, ME 04105
(401) 284-1827 Business
http://www.teraspeed.com
On Wed, May 13, 2015 at 10:33 AM, CHASTANG Cyril <
cyril.chastang@xxxxxxxxxxxxxxx<mailto:cyril.chastang@xxxxxxxxxxxxxxx>>
wrote:
Hi Mo Han,
If your channel is on the same board, it is better to add the AC coupling
capacitor near the receiver in order to minimize impedance mismatch.
Indeed, rise/fall time are bigger near the receiver due to the loss of the
channel and so, the signal spectrum will be narrower.
BR
Cyril
[@@ THALES GROUP INTERNAL @@]
-----Message d'origine-----
De : si-list-bounce@xxxxxxxxxxxxx<mailto:si-list-bounce@xxxxxxxxxxxxx>
[mailto:si-list-bounce@xxxxxxxxxxxxx<mailto:si-list-bounce@xxxxxxxxxxxxx>]
De la part de Havermann, Gert
Envoyé : mercredi 13 mai 2015 16:23
à : hanmoggq@xxxxxxxxx<mailto:hanmoggq@xxxxxxxxx>; si-list@xxxxxxxxxxxxx
<mailto:si-list@xxxxxxxxxxxxx>
Objet : [SI-LIST] AW: AC coupling capacitor
It doesn't make much different as long as it is on the same Board. For
pluggable Cannels each standart requires the Caps to be in a special
position (IEE: Receiver side; PCI: Transmitter side).
BR
Gert
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Von: si-list-bounce@xxxxxxxxxxxxx<mailto:si-list-bounce@xxxxxxxxxxxxx>
[mailto:si-list-bounce@xxxxxxxxxxxxx<mailto:si-list-bounce@xxxxxxxxxxxxx>]
Im Auftrag von mo han
Gesendet: Mittwoch, 13. Mai 2015 15:02
An: si-list@xxxxxxxxxxxxx<mailto:si-list@xxxxxxxxxxxxx>
Betreff: [SI-LIST] AC coupling capacitor
Hi experts:
I found some design place the ac coulping capacitor near the receiver,
others place it near the transmitter, which design is better?
Thanks!
Mo Han
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