Value for AC ground

Discussion in 'General Electronics Chat' started by skyjeff185, Jan 27, 2007.

  1. skyjeff185

    Thread Starter Member

    Jan 27, 2007
    13
    0
    Hi, I am new to circuit design and just to ask a simple question.

    I am designing an MP3 player, general for AC ground, what value of C should I use? or does it matter at all? And also how to test its quality?

    Thx
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    I do not understand your question. For instance, is the value of the capacitor the one to filter the output of the D to A output? The quality of the capacitor is set forth in the manufacturer's spec's.
     
  3. skyjeff185

    Thread Starter Member

    Jan 27, 2007
    13
    0
    Let me rephrase the question i guess...

    You use capacitor as AC ground. But what's the capacitance value people usually choose for AC ground. And how to tell the quality of AC ground is actually good or not. Also the AC ground is use for DC power source.

    Thx
     
  4. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    What do you mean by AC ground? Where is this mentioned in any documentation you have? Where is this online?
     
  5. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    Are you putting a capacitor in series with with the PCB ground and the case..???
     
  6. skyjeff185

    Thread Starter Member

    Jan 27, 2007
    13
    0
    Yes capacitor in series with ground. It is for the power input for two ICs. 1 is STA013 MP3 decoder (which take 5V DC input) another is DAC CS4334 (which takes 3V DC input).
     
  7. wireaddict

    Senior Member

    Nov 1, 2006
    133
    0
    Are you using a regulated 3 & 5 V power supply for the MP3 player? If so, are you designing this, too? If you're using an "off the shelf" supply the only additional capacitance you should need at the + DC inputs of these ICs is 0.1 uF. Install them between + DC lines or "rails" & the circuit common or ground & as close as possible to the ICs & also several other places on the +3, +5 power rails.

    The main purpose of these caps isn't to reduce AC ripple but to conduct any AC noise from the circuit that may have gotten on the DC power rails to ground. I hope this is what you were referring to.
     
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