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Why need crystal for microcontroller?

Discussion in 'Microcontrollers, Programming and IoT' started by matramlee, Apr 8, 2013.

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  1. matramlee


    Apr 8, 2013

    im a mechanical student...but im really love to learn about electronic.....

    i have some question here.....

    if anyone can tell me why do we need crystal for microcontroller??? what is actually the function of the crystal....

    and why must we put capacitor to the each end of the crystal?:)
  2. davenn

    davenn Moderator

    Sep 5, 2009
    hi there
    welcome to the Electronics Point forums

    The crystal is the clock oscillator for the microPU. From that osc. the micro does all its timing functions
    The 2 capacitors often ~ 20 - 30 pF are just part of the oscillator circuit

  3. matramlee


    Apr 8, 2013
    what is actually the function of capacitor?? in what condition will require the capacitor...
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Read this application note on crystal oscillators and component selection. It is for PIC microcontrollers but the rules are the same for other chips, too.
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    A quartz crystal is an accurate way to generate a clock frequency. If accuracy is not required, you can also use a ceramic resonator, or an RC (resistor-capacitor) oscillator. Many microcontrollers have a built-in RC oscillator that can be used f high accuracy is not needed; this reduces the number of components needed.
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