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Altera_Forum's avatar
Altera_Forum
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9 years ago

Configure 3.3V outputs on MAX7000

Hi, I want to supply a MAX7000 with 5V and have most of the I/O using TTL inputs & outputs. I also want to have 8 bidirectional pins at 3.3v. I see the option in Quartus to set the ...
Altera_Forum's avatar
Altera_Forum
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9 years ago

If the device is to drive a signal out at 3.3V then VCCIO needs to be 3.3V - there's no clever internal step-down if you're powering from 5V.

Since MAX7000 devices only have a single internal VCCIO rail, from which all IO buffers are powered, you'll have to use some external circuitry to do the level shifting. Which way round you do this will depend on your requirements - power the whole thing at 3.3 and step up to 5V with buffers or vice-versa. However, given you're requirement for a bi-directional bus at 3.3V, in the interests of reducing the complexity of controlling the direction of external buffers, I'd be tempted to operate your I/O at 3.3V and use buffers to solve your 5V I/O.

Cheers,

Alex