As I know only SATA allows DC coupling and I wonder why PCIe, SAS and other serdes don’t allow so (correct me if DC coupling is actually in the standard). Is this bcs normally an AC common voltage produced by the chip can easily go above the 150mV limit for AC coupling? -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of steve weir Sent: Sunday, October 26, 2014 8:12 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Fw: AC or DC Coupling Selection If you DC couple then you need to look at the CMR of the receiver, the CMV of the transmitter, and the amount of CM noise that can exist between the two in your application. CM differences are common between FPGA SERDES that seek to accommodate many signaling standards and ASICs / ASSPs built to a particular standard. AC coupling is common practice with FPGA SERDES. Coupling capacitors reject CM differences between the Tx and Rx that occur below the cut-off frequency. OOB signaling in some standards have stuck us unpleasant side-effects of low cut-off frequencies and large coupling capacitors. They also do less than nice things for TIE in the timing recovery. Steve. On 10/25/2014 11:55 AM, Ajay Dhingra wrote: > > > -------- Original Message -------- > Subject: Re: [SI-LIST] AC or DC Coupling Selection > From: Ajay Dhingra <ajay.dhingra@xxxxxxxxx> > To: Orin Laney <olaney@xxxxxxxxx> > CC: si-list@xxxxxxxxxxxx > > The data rates are around 6Ghz and 8b/10b is also there. > I mainly want to understand how Vcm difference has impact specially in DC > Coupled interface and what are potential reasons of Vcm differences. > > What kind of implementations in Rx helps mitigate the Vcm difference problem. > > Ajay > > Sent from my Huawei > Mobile---------------------------------------------------------------- > -- > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > List forum is accessible at: > http://tech.groups.yahoo.com/group/si-list > > List archives are viewable at: > //www.freelists.org/archives/si-list > > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > -- Steve Weir IPBLOX, LLC 1580 Grand Point Way MS 34689 Reno, NV 89523-9998 www.ipblox.com (775) 299-4236 Business (866) 675-4630 Toll-free (707) 780-1951 Fax All contents Copyright (c)2013 IPBLOX, LLC. All Rights Reserved. This e-mail may contain confidential material. If you are not the intended recipient, please destroy all records and notify the sender. ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List forum is accessible at: http://tech.groups.yahoo.com/group/si-list List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu