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Altera_Forum's avatar
Altera_Forum
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13 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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13 years ago

Thank you for the reply Oliver!

AC coupling is the best solution, but as the layout stands, it makes it a little hard to add the 4 resistors needed for a proper termination. That is the reason I am looking at DC coupling.

The oscillator has the following LVDS output specs: Vcm = 1.2V Vod = 0.35 Vpp

The Cyclone IV specs say that Vcm should be between 1.05V and 1.55V for that data rate I am using.

That sounds like I am within the specs, is that correct?