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Cyclone IV using differential clock inputs with VCCIO at 3.3V

Altera_Forum
Honored Contributor II
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Hi all, 

 

I'm considering using a Cyclone IV for a small project. The main requirement is that I have to input a differential clock to the FPGA. The differential clock has the LVDS or LVPECL standard. 

 

I'm considering the DE0-Nano board because it has 2 pairs of DIFFCLK_p/n conveniently connected to expansion headers. I noticed all IO banks on the DE0-Nano board are powered at 3.3V. I also noticed VCCIO requirement for LVDS signals is 2.5V (not 3.3V). 

 

My question is whether LVDS will work for clock inputs when VCCIO is 3.3V. 

 

Thank you in advance
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Altera_Forum
Honored Contributor II
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--- Quote Start ---  

My question is whether LVDS will work for clock inputs when VCCIO is 3.3V. 

--- Quote End ---  

 

There's no specified differential I/O standard with 3.3V VCCIO. Plausibility considerations and experience tell, that it can work, at least with reduced performance. The achievable common mode range has to be evaluated. 

 

You'll need to specify a "fake" VCCIO of 2.5V for the respective bank.
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