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Altera_Forum's avatar
Altera_Forum
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15 years ago

Cyclone III with 5v inputs

I'm trying to connect approximately (16) 5v TTL inputs into a Cyclone III eval board, the terasic de0 [1]. These are all input towards the FPGA only. The eval board has (2) 40-pin IDC headers for t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

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it appears they forgot to include the schematic for the protective circuits, but they do mention that they exist.

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Where do you see this mentioned? My simple conclusions from clamp diodes missing in the schematic is, that they have been omitted. If you have the board, you are easily able toc check, if they are present though.

In my opinion, 500 ohm series resistance isn't too high for slow and medium speed signals. Another option for 5 to 3.3V conversion not yet mentioned is a simple resistive divider.