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Altera_Forum's avatar
Altera_Forum
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17 years ago

Cyclone ii, VCCIO 2.5V and 3.3V input

Hello everybody,

is it possible to connect 3.3V to an input located in a bank configured to VCCIO 2.5V without e.g. an external resistor for voltage translation? Is the input 3.3V tollerant in this case? Clamping diode to be configured?

According to table 10.1 in the handbook it should be possible to connect 2.5V and 3.3V to inputs configured either as 3.3V or 2.5V.

But I am not sure whether this information is only valid for banks with a VCCIO setting of 3.3V.

Thanks for any answer,

Volker

2 Replies

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

    --- Quote Start ---

    I/O standard 2.5V in the said table and elsewhere means mainly VCCIO of 2.5 V. It's not generally required to enable PCI clamp diodes when overdriving the input, but should be done, if you expect an overshooting input signal.

    --- Quote End ---

    Thanks for your answer FvM. Then my setting is fine :)
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    17 years ago

    --- Quote Start ---

    But I am not sure whether this information is only valid for banks with a VCCIO setting of 3.3V.

    --- Quote End ---

    I/O standard 2.5V in the said table and elsewhere means mainly VCCIO of 2.5 V. It's not generally required to enable PCI clamp diodes when overdriving the input, but should be done, if you expect an overshooting input signal.