Does DC-Coupled link work for SLVS-EC with 7-Series Transceiver?

[nsy_0415@hotmail.com]

Looking at the Artix 7 FPGA Datasheet, the transceiver common mode input voltage is equivalent to two third of GTP analog supply voltage (Typical 1.2V * 2/3 = 0.8V)

The Image Sensor Output having 160mV<Vcm<260mV common mode voltage.

Does this mean there is no way to implement DC-Coupled link for SLVS-SC with Artix7 GTP?

Any suggestions?

[karnanl]

Hello nsy_0415@hotmail.com 

Yes, your understanding is correct. The link will not work.
Do you have any particular reason using DC-coupling ? AC coupling will work just fine for your usecase.

I see some GTX users using DC coupling for their system, but most of them use it because they have to.
For example users may use data decoding without a good DC balance (i.e. 8B10B encoding is not used, Data-Scramble is not used etc ) so AC coupling is not an option.
For your case, SLVS-EC is using 8B10B encoding, so I don't see any reason for not using AC-coupling.

Thanks & regards
Leo

[nsy_0415@hotmail.com]

Hello @karnanl ,

Thanks for the confirmation.
According to the Artix-7 datasheet, the spec for differential peak-to-peak input voltage is min:150mV & max: 2000mV

while the AC swing for SLVS-EC is 140mV<Vdiff(ac)<290mV.

Is it risky to use AC-coupled in this case as well?

[karnanl · Accepted solution]

Hello nsy_0415@hotmail.com 

I think those numbers are the spec value.  Sony sensors have a programmable output swing level. (please confirm on each sensor datasheet)
So, if you can ensure that peak-to-peak input voltage at GTP transceiver input pin is larger than 150mV, AC-coupling connectivity should be okay.

Regards
Leo