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Altera_Forum's avatar
Altera_Forum
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15 years ago

Cyclone IV receiving 5V PECL

I want to drive differential input pairs with 5V PECL. Can I use the diff input with a 3.3V VCCIO or is this prevented? If I can, what is the max common mode and max input voltage? I'm considering DC...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

The differential inputs aren't specified for 3.3V VCCIO, thus I won't use it.

The LVDS common mode input range has different specifications depending on the speed, e.g. with Cyclone IV maximum VCM is 1.55 V for hghest data rate. Considering the high differential level of PECL, an impedance matched resistive divider will do, like 120/80 ohm.