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Original question:

CDCE925: Connecting two more CDCE(L)9x onto the same I2C bus - how to addr each one?

CDCE925: CDCE949 Clock Generator

JOE
Prodigy 40 points
Part Number: CDCE925
Other Parts Discussed in Thread: CDCE949, SN74LVC2G157, LMK00105, CDCE6214, CDCM6208

Hi,

I am using CDCE949 clock generator. I want to disable one of the clock generator pin and use external clock source with SMA connector through header For example First scenario,If I want to use SMA connector,SMA will connect to MCU.Second scenario, If I want to use clock generator, Clock generator will  connect to MCU. Can I use clock generator instead of oscillator like in the picture?

  • 0
    TI__Mastermind 20900 points

    Hello,

    you can use an crystal oscillator or the external MCU input. The CDCE949 needs to be configured to LVCMOS input. The input signal needs to be applied to Xin/CLK pin1.

    Note, that the input signal swing should be 1.8V typical. You may need a resistive voltage divider at the input pin, when you try to drive with 3.3V signals.

    Regards,

    Julian

  • 0 in reply to Julian Hagedorn
    Prodigy 40 points

    Hi Julian,

    Thank you for your interest. I didn't explain exactly what I meant. I connected the output pin of the clock generator to the private pin of the MCU.
    I want to give frequency to the same special pin with SMA connector. If the user wants, User can give frequency from SMA or choose between clock generator and SMA. I thought of using the header as in the picture above. Does the clock generator work properly with this method? Is there a sample work where the output of the Clock generator is connected to the SMA? What would you suggest me to do?

    Regards,

    Esra

  • +1 in reply to JOE
    TI__Mastermind 20900 points

    Hi Esra,

    routing a clock signal via a pin header is not ideal. That will harm the signal integrity. A better way of doing that is to use a multiplexer. For example LMK00105 for high performance or this SN74LVC2G157. Here you can use a pin header to select which input to use.

    Another alternative is to use a clock generator that has 2 inputs. For example CDCM6208 or CDCE6214.

    regards,

    Julian