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Altera_Forum's avatar
Altera_Forum
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8 years ago

Routing a 5V signal through a 3,3V Cpld. Is the output 5V or 3,3V?

Hi, I'm using an old Altera Cpld in a project, a Max 7000 series, which needs a 3,3V Vcc but the IOs are 5V compatible.

So, if I put a 5V input IO and route it to other output IO, this output will be 3,3V or 5V? By routing I mean a direct connection in my vhdl code.

I have some 5V inputs, and I want to put a 3,3V chip behind the Cpld, so I'm expecting that the output would be 3,3V, otherwise I can't use this approach.

Sorry if it's a newbie question.

Thanks...

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    As the CPLD is powered by 3.3V, the outputs cannot be higher voltage than these 3.3V ;-)

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    --- Quote Start ---

    Hi, I'm using an old Altera Cpld in a project, a Max 7000 series, which needs a 3,3V Vcc but the IOs are 5V compatible.

    So, if I put a 5V input IO and route it to other output IO, this output will be 3,3V or 5V? By routing I mean a direct connection in my vhdl code.

    I have some 5V inputs, and I want to put a 3,3V chip behind the Cpld, so I'm expecting that the output would be 3,3V, otherwise I can't use this approach.

    Sorry if it's a newbie question.

    Thanks...

    --- Quote End ---

    You may also check the device datasheet for further details on the expected output voltage. However, as Calhermann mentioin, if the chip is powered by max 3.3V, the max output IO voltage should be capped at 3.3V. For the input, there might be some internal clamping which allow it to interface with 5V.

    Best Regards,

    bfkstimchan

    (This message was posted on behalf of Intel Corporation)