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Reverse voltage on DC/DC

Discussion in 'General Electronics Discussion' started by johnny_cash, Sep 13, 2013.

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  1. johnny_cash


    Aug 13, 2013
    Hello everybody,

    I have a trouble: basically, i have an isolated DC/DC converter (VIN/VOUT), "plug'n play (no external components required). DS:

    primary: +5v/GND1 which should go to Vin+/Vin-
    secondary: Vout+/Vout- that shoudl provide +3.3v/GND2

    unfortunatly, my PCB is badly wired: +5v/GND1 to VIN-/VIN+ and VOUT+/VOUT to GND2/+3.3v; Totally reversed on both input and ouput.

    I have no skill in unsoldering the DC/DC. However, to continue my job, could i simply power the secondary, without having my primary powered ? It would imply to have +3.3v on VOUT- and GND2 on VOUT+ on secondary side of the converter.

    I know this is not something good, but can it be possible or would it definitively harm my converter (and impact the primary side of the board) ?

    Thank you for you advices, JC
  2. BobK


    Jan 5, 2010
    It would be safer to cut one of the traces from the DC / DC, isoltating it from the supplied voltage.

  3. johnny_cash


    Aug 13, 2013
    thank you for this advice. Unfortunatly, i think the traces are on layers 2 & 3. Do you think:
    - it could harm the primary
    - it could harm the DC/DC

    I always heard theses beasts are rock solids... :)
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