De-coupling capacitors

Discussion in 'General Electronics Chat' started by cameo, Jul 9, 2007.

  1. cameo

    Thread Starter New Member

    Jul 9, 2007
    8
    0
    Hi

    I am here to get an expert help.
    I have a board designed for embedded applications,consisting of a processor,RAm,Rom etc.And i could see there are lot of de-coupling capacitors around those chips.
    The problm is my board is not stable.Doesnt work sometimes.Does these decoupling capacitors got to do something with that.I figured a small error,i have assembled a 1uF/6.3V smd caps( i ahv only that value) instead of a 1uF/16V smd cap(told in the AN) which is for the RAM IC.Will that voltage difference create problms..?
    Definitely need an expert opinion on this.

    Regards,
     
  2. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    I don't think is not from these filter capacitors. It might be a contact problem or so. Also, the cap that you replaced should be fine if your circuit works at 5V, although I suggest a 10V capacitor. The voltage rating of a capacitor states the maximum DC voltage it can handle. Operation will not be guaranteed at a higher voltage than the stated and you might disrupt the dielectric of the capacitor, with bad consequences (the capacitor might explode).
     
  3. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Decoupling capacitors play an important role in preventing the introduction of disturbances on the power supply bus by the devices present on the printed circuit board. It is equally important, if not more so, that the power supply bus be as stable and spike free as possible.

    Also beneficial are large valued filter capacitors placed on the power bus close to entry point of the power.

    In the process of troubleshooting the cause of the unstable behaviour of your microprocessor based design, you need to confirm that the power supply feeding the devices is well regulated and that it possesses more than enough power to supply your circuitry during those periods of greatest power demand (i.e. running motors, energizing relays, etc).

    Good Luck,
    hgmjr
     
  4. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    I noticed that the capacitors might be to small. You need just one capacitor, big enought to satisfy the demands of your circuit. Also, you should consider using a voltage regulator, if you are not using one.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Assuming you've got 2 or 3 volts across the capacitor, there should be no problems. In some other application with 12 V or something there could be a problem, but such is another story.
     
  6. cameo

    Thread Starter New Member

    Jul 9, 2007
    8
    0
    yes,its 1.8V.
    Thanks to all.From your replies,i came to a conclusion that those capacitors are not creating any problems in my board.


    Cheers,
     
Loading...