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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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can i attach the output of the ti chip directly to the connector going to the cyclone iii? ie without a series resistor?

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Yes. If a source termination is required, it would be needed back at the source driving the input to the bus switch.

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should i connect the fpga ground to the ground of the system i'm receiving the 5v ttl from?

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Yes. Without it, your interface will not work.

If you need an isolated interface, then Analog Devices has some nice parts; look for iCoupler.

Cheers,

Dave