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Altera_Forum's avatar
Altera_Forum
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16 years ago

output as mosfet p-ch switch

Hello,

I want to use cyclone III's output as a mosfet P-ch switch.

When the output will be defined low - the mosfet will be opened.

When the output will be defined HI-z - the mosfet will be closed (I have pullup between G and S of the mosfet).

Is it OK that when the output will be defined as HI-z, it will be short-circuited to 12V?

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    A FPGA has maximum voltage and current ratings for pins, that have to be kept unconditionally.

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    yes. Even id the output is at Hi-Z you will still damage the device

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    I understand.

    Just to make sure. Your answer is relevent even if te output is at HI-Z?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    Maximum voltage ratings for Cyclone III and other FPGAs are specified very detailed in device handbook. You shouldn't apply I/O voltages above 3.3V (plus a small overhead). Voltages above 4.3V must be expected to damage the device immediately. You need some kind of level converter.