DVPPIN vs BER Eye Mask

[cornonthecob]

In the GTH IBIS-AMI Simulation Kit, there is a BER contour mask provided that has minimum eye height of +/- 30mV. However, in the Kintex Ultrascale datasheet, the GTH specs in table 48 list a parameter DVPPIN (differential peak-to-peak input voltage) that has a minimum value of 150 mV. It seems like DS892 is saying the minimum eye height should be +/- 75 mV. Is there a difference in the meaning of these two parameters? Which should I use to validate my signal integrity simulations?

[eschidl]

Hi @cornonthecob ,

There is indeed a difference. The datasheet voltage values apply to the actual package pins (This does not define eye height.). And the BER mask is for the eye height at the data sampler after equalisation (means inside the RX).

You should follow both specifications.

[cornonthecob]

Hi @eschidl ,

I appreciate your response. Hopefully you can clarify one more question. I guess I don't understand the meaning of differential peak-to-peak input voltage. If the eye is closed at the package pin and then recovered inside the GTH receiver, won't the differential peak-to-peak voltage at the pin be less than 60 mV (BER mask requirement) by definition?

[eschidl]

Hi @cornonthecob ,

as I mentioned already, the definition on the package pins is not related to the BER mask.

It is about the voltage levels that need to be present on the inputs so that the signal is either recognised or is not damaging the input. For example, the minimum differential pkpk Voltage of 150mV would mean that you should have a minimum voltage swing of 75mV on the signle ended lines.

[roym]

The eye can be completely closed while you still have 150mv p-p.  The eye is taken with the scope set to infinite persistence of thousands of samples of 1's and 0's while the p-p would be the average of maybe a thousand cycles of a one going to a zero.