drive LVDS clocks with a spartan3

Nov 09, 2006 1 Replies

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Hello,

I work as Design Engineer at Bull SAS in France (Server Design and Development).

I saw a webcase on the web in which someone try to provide some guidance concerning LVDS signals. I am not sure to have understood all your answers, so please let me ask the following question :

I am currently working on a design based on the spartan XC3S1000.

Can it be used to drive LVDS clocks ? (LVDS clock's frenquency is 100 Mhz).

If yes, what output buffers should we use ? (Is there an "OBUFGDS" in the XC3S1000 ?).

What will be the maximum jitter between these 100Mhz-LVDS clocks ?

Thanks a lot for your answers, Julien

You can use the OBUFDS for differential output. You should be able to the same with I/O constraints. You will need to use an bank voltage of

2.5V for output LVDS operation.

There will be a skew between output pairings. If they are clocked outputs with flip-flops in the I/O then that is related to differences in internal clock routing delays.If you are just doing a route through from a clock source there will be variance due to differences in internal routing delays. There will also be small variance due to bond out wires/routing.

Jitter will depend on your clock sources. If you use a DCM there will be jitter related to that. Your origional clock source will have jitter too and that can be impressed on outputs.

John Adair Enterpo> Hello,

drive LVDS clocks with a spartan3

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