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21615 Discussions

cyclone IV I/O standard

Altera_Forum
Honored Contributor II
‎04-28-2012 12:09 PM
1,208 Views

Hi, 

I am using ep4ce30f29c6 (fbga780pin) with aproximately all IO in use. because of the need to use on chip termination, I use 3-volt as vccio. my main worry is that other parts in my design are 3.3volt. do I need to use pci-clamp diode for all inputs and also series termination on external drivers (feeding fpga)? 

because of huge number of IO and considering clamping diode, will dissipation be critical and noticable? is it possible to interfacing with 3.3vot without clamping diode (disabling clamp diode)-it damage fpga or not? what is the value of forward voltage of clamp diodes? 

 

thank you very much for your reply. 

 

Ramin:confused:
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Altera_Forum
Honored Contributor II
‎04-28-2012 04:06 PM
501 Views

Clamp diodes are silicon diodes with respective forward voltage. Exact data can be e.g. derived from IBIS files. With 0.3 V forward voltage, diode current will be low. I think however, that reasonable source side impedance matching of fast digital signals to the FPGA can obviate the need for clamping diodes.

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Altera_Forum
Honored Contributor II
‎04-28-2012 05:20 PM
501 Views

Thank you very much for your reply 

 

Ramin
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