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Altera_Forum's avatar
Altera_Forum
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14 years ago

Can VREF be other than VCCIO/2?

Must VREF be equal to 1/2*VCCIO, or can it be, say, 2/3*VCCIO? BTW, I'm using a Cyclone III M164 package. (very small physical board constraints) I'm trying to interface to a chip that has...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

This seems to be a rather unusual problem, because regular DDR designs need a VTT driver, which can easily supply VREF as well. VREF input current in unconfigured state is meaningless, I think, but I would suggest a lower divider impedance than 500 ohm and of course effective bypassing.