What is the specification for the crystal used on the AN2131-DK001 EZ-USB  development board?

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    Question: What is the specification for the crystal used on the AN2131-DK001 EZ-USB  development board?

     

    Answer:

    The crystal Spec is

    - Frequency of 12.00 MHz +-2000 ppm

    - In fundamental-mode operation

    - Parallel resonant

    - Effective series resistance of 30 ohms

    - Power dissipation of 1 mW.

     

    See the schematic found in C:\Cypress\USB\Hardware\EZ-USB Fx\DEVBD REVB\SCHEMATIC PDF'S for the EZ-USB FX and C:\Cypress\USB\Hardware\EZ-USB Series 2100\DEVBD REVD for the EZ-USB for the circuit diagram.


    The load capacitors, C1 and C2, should be chosen so that the equation below is satisfied. CL is the load specified for the crystal. CL = ((C1 * C2)/(C1 + C2)) + CSTRAY

    For C1 = C2 the equation is:

    CL = 0.5*C + CSTRAY, where C = C1 = C2

    Solving for C:

    C = 2*(CL-CSTRAY) For CSTRAY = 5 pF and CL = 20 pF

    The value for each of the two load capacitors is: C = 2*(20-5) = 30 pF

    A more available value, but not out of range so that frequency will be affected is: C1 = C2 = 27 pF.

    For typical crystals, C1 and C2 will be in the range of 20 to 33 pF.