[SI-LIST] Re: AC Coupled Signals
- From: "OPREA Dorin" <Dorin.Oprea@xxxxxxxxxxxxxxxxxx>
- To: <jory_mckinley@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 25 Sep 2007 08:28:30 -0500
Hi Jory,
Considering the via and pad along the line discontinuities - does the
number of the discontinuities change with the series cap placement? Does
the routing compensate for the via and pad effect on the signal?=20
Regards,
Dorin
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Jory McKinley
Sent: Monday, September 24, 2007 5:32 PM
To: leeritchey@xxxxxxxxxxxxx; npatel@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: AC Coupled Signals
I will elaborate a bit on what I have seen. I have measured (time
domain) in the lab some effects that appears to be location specific in
the placement of the AC coupling caps at the rcvr. Now this may be due
in part to the fact that I am using 50-ohm resistor termination in each
lead as well and the combination (cap plus rcvr reflection) is giving
some imbalance depending on distance. The best rcvr eye that I am
seeing is when I can move the AC/term as close to the rcvr as I can. By
the way these are 5Gb/s signals.
If I have time I will try and isolate what I am seeing and even simulate
it, has anyone else seen or simulated this?
-Jory
----- Original Message ----
From: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
To: "npatel@xxxxxxxxxx" <npatel@xxxxxxxxxx>; si-list@xxxxxxxxxxxxx
Sent: Monday, September 24, 2007 1:06:06 PM
Subject: [SI-LIST] Re: AC Coupled Signals
Nikil,
I have made measurements on test PCBs and the location is not all that
important. In identical pairs, one with AC coupling capacitors and the
other without, the loss vs. frequency is virtually identical at leas out
to
6 GHz. That would be 12 Mb/S.
Lee Ritchey
> [Original Message]
> From: <npatel@xxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 9/24/2007 10:21:37 AM
> Subject: [SI-LIST] AC Coupled Signals
>
> Hi all,
> In case of AC coupled signals does anyone know of an optimum placement
> for the caps? I mean should they be placed near the source, receiver,=20
> middle of the transmission line?
> How much difference does it make in the opening of the eye?
> The signals are differential CML running at 3.0Gbps
>
> Thanks,
> Nikhil
>
>
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