Friday Free Board Quiz – the prize is A20-OLinuXino-LIME – Crystal Resonators Load Capacitors


A20-OLinuXino-LIME is our popular Linux OSHW computer.

You can win this board! To participate in the Quiz is enough to re-tweet the Twitter Quiz announcement message.

To double your chances you have to answer the Quiz question :)

The Quiz question is: How load capacittors are calculated for crystal resonator which operates in serirs resonance?

You have time to re-tweet and/or answer until Monday 29nd of February.

In Monday we will post the correct answer and ask to generate random number in range then announce the winner and ship the board by post/airmail.

Good Luck!

11 Comments (+add yours?)

  1. inakizi
    Feb 25, 2016 @ 22:02:59

    It depends on the Load Capacitance of the Crystal to be used (CL) and the stray capacitance (Cs) of the PCB. Basically the series capacitance of the capacitors (C1 and C2) plus the stray capacitance must be equal to the Load Capacitance of the used crystal. So:

    CL = (C1*C2)/(C1+C2) + Cs

    So usually C1 and C2 are slightly lower than double CL.


  2. bremenpl
    Feb 26, 2016 @ 07:09:34

    In series you dont use load caps.


  3. Prashanth Mypadi
    Feb 26, 2016 @ 13:57:14

    As per my knowledge, load capacitance is not defined for crystal resonator operating in series. It is taken as zero


  4. Prashanth Mypadi
    Feb 26, 2016 @ 14:09:12

    Load capacitor is not used in series resonant crystals


  5. Alex
    Feb 26, 2016 @ 23:24:04

    CL: load capacitance crystal
    CI: capacitance of uC port
    CP: capacitance of PCB wire

    C1,2 = 2x (CL – CI – CP)


  6. TKroenert
    Feb 27, 2016 @ 12:55:04

    @Alex: That what I’ve seen in atmels SAM3S datasheets!

    C = 2x (CL – CI – CP)

    CP is mostly between 1 and 2 pF.
    CI is somethimes not specified (p.e. old freescales).

    PRO-TIPP: Use coolant spray (CRC 75) and a heatgun and test,test,test!

    A few years ago I had a pcb which only works correctly in the summer month.. and I had used NPOs for the crystal!


  7. Laskaridis Laskaris
    Feb 29, 2016 @ 15:35:25

    Hi, load capacitor is not used


  8. x x
    Feb 29, 2016 @ 15:38:53

    Hi, load capacitor is not used


  9. Veselin Dimitrov
    Mar 01, 2016 @ 08:25:35

    For a series resonant circuit a load capacitor is not needed.


  10. x x
    Mar 02, 2016 @ 11:27:34

    Good morning, so… the winner is ???


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