CY2305 Behavior on Removal of Input Reference - KBA82621

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    Version: **

     

    Question:

    What is the effect on the CY2305 output when the input reference clock is removed?

     

    Answer:

    The output usually holds the original frequency for only a few cycles. Generally, you cannot expect more than two or three cycles at the normal frequency. It then drops toward a lower frequency. 

    For example,

    100 MHz drops towards 80 MHz, stops after ~120 cycles
    80 MHz drops towards 70 MHz, stops after ~120 cycles
    60 MHz drops towards 50 MHz, stops after ~90 cycles
    40 MHz drops towards 30 MHz, stops after ~50 cycles
    20 MHz drops towards 14 MHz, stops after ~25 cycles
    10 MHz goes very quickly towards 5 MHz, stops after ~10 cycles

    In all cases for the frequencies above, the output clock stops about 1.5 to 2 microseconds.