Optocoupler - emitter pull down

Discussion in 'Digital Circuit Design' started by Arne Spiessens, Oct 25, 2017.

  1. Arne Spiessens

    Thread Starter New Member

    Nov 8, 2016
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    Hello,

    I want to use this optocoupler ILD205 ( https://www.vishay.com/docs/83647/ild205t.pdf ) for driving a PROFET (MOSFET basically) from a microcontroller MCU1.1
    The output will now always be inverted, which I don't want. I can revert it with a logic CMOS inverter, but I want to avoid extra components.
    Can I use a pull down resistor from the emitter to GND and no pull up resistor?
    I know a lot of optocouplers are not designed for this, but the ILD205 seems to be alright with it?


    Kind regards
     
    Last edited: Oct 25, 2017
  2. bertus

    Administrator

    Apr 5, 2008
    18,584
    3,596
    Hello,

    What is the box with the P$ pins in it?
    You can exchange the R5 and opto-output, but it will effect the timing, as you will have R5 parallel with C9.

    Bertus
     
  3. Arne Spiessens

    Thread Starter New Member

    Nov 8, 2016
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    0
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Why do you have C9 in the circuit?
    Do you want a delay on switch off (when the opto opens)?

    Bertus
     
  5. Arne Spiessens

    Thread Starter New Member

    Nov 8, 2016
    17
    0
    I will not use this circuit for fast switching, the PROFET should turn on and stay on for hours. So It's not bad I think to make the circuit a bit slower reacting I believe
     
  6. bertus

    Administrator

    Apr 5, 2008
    18,584
    3,596
    Hello,

    Then remove C9 and switch R5 and the opto-output.

    Bertus
     
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