[SI-LIST] Re: PCI Express AC coupled signals
- From: "Kinger Cai" <kinger.cai@xxxxxxxxx>
- To: helen.tao.xu@xxxxxxxxx
- Date: Wed, 14 Nov 2007 19:25:07 -0700
The massive sweeping simualtion indicates that there is insignificant
difference for the AC Capactor placement. In other side, you can even
include two AC capcitors one at both Tx and the other at Rx side. Again, it
should be fine, as soon as a sufficient AC Capcitor involved in the channel.
That general guideline is really helping us not to leave the AC Capcitor out
of the channel, since the Tx module adn Rx module will be developed by
different vendors.
Kinger consultant Advance
www.Kingercai.com
On 11/14/07, tao xu <helen.tao.xu@xxxxxxxxx> wrote:
>
> Hi, Ivor
> The placement position of capacitor will effect a little bit about jitter
> of
> channel. You can use a simulation tool to investigate relationship
> jitter/postion of capacitor. Of cource, you can put cap on receiver side
> if
> you have enough timing margin. But if your timing is tight. a simulation
> to
> find best postion for AC cap is recommended.
> thanks and regards
> Tao (helen )
> On Nov 15, 2007 5:47 AM, Ivor Bowden <ivorlist@xxxxxxxxxxx> wrote:
> > Thanks to all who replied :-)
> > All replies confirm this should be OK, I expected as much, but it is
> > good to have consensus!
> > Ivor
> >
> >
> > on 11/14/2007 7:43 AM PDT Ivor Bowden wrote:
> > > Any reason why not to locate the PCI Express coupling caps at the
> > > receiver on a system board implementation? I know PCI Express Base
> > > Specification section 4.3.1.2 calls out "The requirement for the
> > > inclusion of AC coupling capacitors on the interconnect media is
> > > specified at the Transmitter", but there are no specific placement
> rules
> > > except the specifications for separate host / card module require that
> > > physical division. Based on the recent "AC Coupled Signals" thread, it
> > > would seem reasonable to place the capacitors at the receiver on a
> > > system board, allowing the advantage that the mounting pads could be
> > > used for probing - eliminating the necessity of separate test points
> at
> > > the RX end.
> > > Thanks,
> > > Ivor Bowden
> > > Hardware Engineer
> > > Curtiss-Wright Controls Embedded Computing
> > >
> >
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