[SI-LIST] Re: DCD Reduction due to Series Caps on Serial IO
- From: steve weir <weirsi@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 05 Apr 2013 10:26:10 -0700
Off-hand I would suspect that your capacitor is closer to the
transmitter than the receiver and is not transparent, at least not with
the scope probe in-place. But this depends somewhat on how you test for
DCD.
Steve.
On 4/5/2013 4:36 AM, vinod ah wrote:
> Hi,
> I am measuring DCD (Duty cycle distortion) on Tx pins of PCIe3 (8Gbps)
> interface connected to a constant load of 50 Ohms (100 ohms differential).
>
> What i see is DCD is more when measured before the AC coupling cap, rather
> than after the cap. Looks like AC-coupling cap (100nF) and 50 ohm load is
> forming a high pass filter.
>
> I am unable to understand cap effect on DCD. Any thoughts here?
>
> Regards
> Vinod A H
>
>
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