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Altera_Forum
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17 years ago

DE-2 5V tolerance

Somebody can confirm if the DE-2 I/O expansion headers are 5V tolerant?

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    DE-2 has 47 ohm series sersistors and BAT54 schottky clamps at all GPIO pins. They basically provide a safe voltage limitation, if operating it from 5 V logic. Considering the voltage drop at the driver, the current would be limited to about 20 mA for each pin. Two problems should be considererd, however:

    - Driving many inputs to 5V with an idle FPGA could possibly raise the 3.3V supply voltage to an dangerous level.

    - With an octal driver chip, the maximum VCC current could be exceeded

    A simple solution would be to use additional series resistors with slow or medium speed signals.
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Many thanks Franck.

    So if I understand you correctly, three or four pins should be ok, more could be risky.