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Thread: how to prevent negative voltage to enter into IC

  1. 13th February 2009 09:54 AM #1
    ponsakthi
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    Default how to prevent negative voltage to enter into IC

    hi all
    i have a 12v to 5 v converter IC.

    there are two points external to the module which are connected to 12v ic input and ground respectively.


    but instead if they reverse the pins and connect 12v to ground pin and 0v to in i/p the ic burns out.


    so what circuitry should ia dd on the input path of the 12v ic i/p to avoid negative voltages through it
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  2. 13th February 2009 10:12 AM #2
    Nigel Goodwin
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    Feed the 12V through a suitably rated rectifier diode.
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  3. 13th February 2009 10:13 AM #3
    ponsakthi
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    diode will dissipate a large amount of heat .. isnt it?
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  4. 13th February 2009 10:18 AM #4
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    Quote Originally Posted by ponsakthi View Post
    diode will dissipate a large amount of heat .. isnt it?
    As you've provided absolutely no details about the current required, how would we know? - but W = V x I
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  5. 13th February 2009 10:21 AM #5
    ponsakthi
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    sorry the module takes 1.2 A of current
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  6. 13th February 2009 10:56 AM #6
    Nigel Goodwin
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    Then the diode will dissipate about 0.84W, use a 3A or 5A diode you should be fine. Bear in mind as well, the regulator will dissipate less power, due to the 0.7V lower voltage supoplied to it.
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