Hi Vinu,
AC coupling capacitors are basically high pass filters. Increasing the
capacitor value will lower the cut off frequency of the filter.
How does that help in baseline wander? Do you mean increased baseline wander
implies excitation of lower frequencies?
Regards
Amit
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Vinu Arumugham
Sent: 13 August 2018 22:49
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: PCI Express 265nF vs. SATA 10nF vs. USB 100nF DC
blocking caps
Baseline wander.
8B/10B code based systems have short run length (number of consecutive 1s or
0s) and is DC balanced over short intervals. Smaller capacitors are ok.
Scrambler based systems can have longer run lengths and DC balance is achieved
over a longer interval. Larger capacitors are needed.
Thanks,
Vinu
On 08/13/2018 01:55 AM, Hermann Ruckerbauer wrote:
Hello,
as there are just some discussions about DC blocking caps (AC coupling
caps) for PCIe I would have another question.
PCIe suggests 100nF for Gen1/2 and updated this to up to 265nF for
Gen3 (guess Gen4/5 will not change) SATA had 10nF for Gen3 @ 6Gb/s I
think USB still stays with 100nF, even for 10Gb/s
what is the real driver and the impact of the height of the Value of
the required capacitor?
What is the impact of a too small/to large capacitor on Signal integrity ?
Anybody to share some insight on this one?
thanks a lot
Hermann
