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Altera_Forum's avatar
Altera_Forum
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14 years ago

AC/DC coupled LVDS on REFCLK

The Cyclone IV requires external termination if using AC coupled LVDS to the REFCLK pins. I have a couple of questions: 1- If the Vcm of the clock generator is compatible with the Vcm required...
Altera_Forum's avatar
Altera_Forum
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14 years ago

Apparently, the CycloneIV Vcm spec you are refering to is attached to some LVDS inputs located in column I/Os whereas in your initial post you were talking about a REFCLK input which belongs to a GXB block.

So, if your clock oscillator is connected to the input reference REFCLK0 or REFCLK1 of a transceiver block, Vicm spec is slightly different (and a bit ambiguous to be true...). Nevertheless, with a 1.2Vcm it will work as well.

If you are not using transceiver but true LVDS inputs, your clock source voltage levels are fully compliant so go ahead ! :-P