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CDC7005: Question about Outputs and (PLL)

Romain Magne
Prodigy 20 points
Part Number: CDC7005

Hi everyone,

I'm considering using a reference clock oscillator (possibly quartz) at 10MHz and utilizing the CDC7005 synthesizer to generate 5 different ouput frequencies higher than the input frequency. Is this achievable?

I have a query regarding the datasheet of the CDC7005 class product, particularly concerning the output frequencies.

Although it's not explicitly stated in the datasheet, can anyone confirm if the 5 frequencies outputs of the component are independent and can be controlled to generate different frequencies?

Additionally, in the datasheet, there's information about : "Each Output Frequency Is Selectable By x1, /2, /4, /8, /16". Does this imply that we can multiply the input frequencies by 1, 2, 4, 8, or 16? The fact that only frequency

division is mentioned leaves me wondering.

Thank you in advance for your response.

  • 0
    TI__Genius 10975 points

    Hello,

    We'll get back to you by the end of the week.

    Best,

    Andrea

  • 0 in reply to Andrea Vallenilla
    TI__Mastermind 18320 points

    Romain,

    The CDC7005 takes the VCXO frequency and divides this down by 1, 2, 4, 8, and 16. Each of the output paths can select one of these divider clocks through their respective multiplexers.

    What are the five frequencies and formats that you require? A device with more flexibility (and an integrated VCO) may be more suitable for your solution.

    Thanks,

    Kadeem

  • 0 in reply to Kadeem Samuel
    Prodigy 20 points

    Hi Kadeem,

    Thank for your answer, well i want to use a ref clock input (10 MHz quartz clock), and use the integrated PLL into the CDC7005, to create a 300 MHz for clock output 1, 54 MHz on output 2, 600MHz, and other clock for 37.125 MHz and 74.25 MHz.

    All these 5 frequencies are independant and each need their own output.

    So instead of divide the ref clock i would use the PLL to multply it and create other clock use into my project.

    Thanks

    Romain

  • 0 in reply to Andrea Vallenilla
    Prodigy 20 points

    Thanks you, i will wait your answer,

    Romain

  • 0 in reply to Andrea Vallenilla
    Prodigy 20 points

    Hi, well i found my answer i will let a comment of what i discovered.

    No need to develop your answer.

    Thank you

  • 0 in reply to Romain Magne
    Prodigy 20 points

    Hi, well i found my answer i will let a comment of what i discovered.

    No need to develop your answer.

    Thank you

  • 0
    Prodigy 20 points

    Hi everyone,

    I've found the solution to my needs and will be closing this question now. Regarding the schematic of the simplified CDC 7005, here it is:

    The five outputs are not truly independent because they are derived from the same reference clock frequency. However, all five outputs are multiples of the desired clock frequency. For instance, if we require a 300 MHz output, we can only obtain frequencies such as 300 MHz, 150 MHz (half of the desired clock), 75 MHz (a quarter of the desired clock), and so on.

    However, I specifically require frequencies like 74.25 MHz, 37.125 MHz, etc. As a result, this chip will not be suitable for my application if i'ts the only synthesizer.

    Thank you once again for the various answers I have received and for your assistance.

    Best regards,
    Romain