V5 Differential Select I/O

Jul 27, 2007 1 Replies
A

Xilinx V5 supports Differential select I/O data rate upto 1250 Mbps. It supports HT_25, LVDS_25 and may other electrical standards. What electrical standard should be used to support the maximum specified data rate of 1250 Mbps? My preference will be HT_25 as it is easy to meet the common mode voltage specification but I am not sure if I can achieve the highest supported data rate with the HT_25 electrical standard.



The LVDS_25 has typical input common mode voltage of 1.2V while the HT_25 has typical input common mode voltage of 600mV. I understand that LVDS_25 has very wide common mode voltage range. But do I get the highest specified data rate if I do not follow they typical voltage specification?



LVDS_25 I think is the most popular standard. Do I have to use 1.2V input common mode voltage for 1.25 Gbps operation? or Can I still get 1.25 Gbps with HT_25 at



600mV input common mode voltage?

Thanks



Aaron


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A

Aaron,

That is why people use signal integrity simulation tools: without running a simulation for your pcb traces, and your driving/driven device(s), your question can not be answered.

The 1.25 Gbs also presumes double data rate (DDR).

A quick "what if" using Hyperlynx SI tool, shows both standards are capable of the speed (ie they switch fast enough, 'eye' is open), but a full simulation for your situation would be required to have confidence that it would work at this speed.

Austin

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