GND Plane and 3 voltages...

Discussion in 'General Electronics Chat' started by bob332, Jul 2, 2011.

  1. bob332

    Thread Starter Member

    Feb 14, 2011
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    have a power board that has 7-20VDC coming in and have regulators that drop it down to 5VDC and then to 3V3VDC. is it ok to use a common ground plane for all the different voltages or should the gnd from the main incoming voltage to the 5VDC reg be seperated from the other gnds? there will only be tracks on the top of the board for signals and positive voltages.

    thanks in advance,
    bob
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    It's pretty typical to use a single ground plane for supplies.

    You might want to post your schematic to get some feedback on it.
     
  3. bob332

    Thread Starter Member

    Feb 14, 2011
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    i actually do not have a schematic for this one finished, but it is pretty simple, raw in is 7-20V, then a 7805 or recom which feeds a 3V3 reg. the 7805/recom has a 10uF in front and after it and the 3V3 reg has a 10uF on its output too. input power will fluctuate so i am not set in concrete on the cap values. i just wasn't sure if the gnd mattered if there are 3 voltages being output, but all tied to the same gnd?
     
  4. #12

    Expert

    Nov 30, 2010
    16,298
    6,810
    The three voltages aren't "tied" to ground. (If they were, they would be "shorted".) The three voltages, and the dozens of voltages that will happen when you attach the final loads, will use a single "ground" to allow their current to complete a circuit back to the source of the original voltage.

    It is common that a mis-interpretation of a word causes confusion. I think this is merely a problem with the definition of a word.
     
  5. bob332

    Thread Starter Member

    Feb 14, 2011
    80
    0
    thx for the clarification
     
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