AD9515 Clock Input general questions


I have to use the clock distributor AD9515 in my design to generate a 250MHz clock, and since it's pretty new to me, I'm not sure what clock input I should use ? 
A simple quartz, another clk generator IC that I will put upstream ... ?

And also, what is the differences between using a 1GHz quartz with a x4 divider or a 250MHz quartz with x1 div ?


Top Replies

  • +1
    •  Analog Employees 
    on Jun 22, 2021 8:25 PM


    in the future, you should post questions related to clocking ICs in the Clock and Timing section of Engineer Zone:

    As you said, the AD9515 is a clock distributor chip. It needs a clock at the input. It does not create it.

    If you want to create a clock of a higher frequency from a crystal resonator, take a look at the AD9576. It can take a 25 MHz crystal resonator and obtain many 250MHz clocks.

    Other smaller chips that can also generate 250MHz from a 25 MHz crystal resonator: HMC1035, HMC1033, HMC1031

    This page provides a comprehensive list:

    Regarding to your last question: whenever you introduce an IC between an input clock and an output clock, noise is introduced. The phase noise of the output clock depends on the input clock profile and the penalty the particular IC introduces. So there is not a clear answer to your question 


  • Thank you for your answer,

    My bad, I was convinced to be in the "Clock and Timing" section of the forum

    Ok this makes more sense to use directly fully integrated clock generator for my purpose, thanks for explanations and for the link.

    Actually my question was coming from the datasheet of the ADC AD9250 p.22 (differential lvds or lvpecl sampling clock) :

    Which suggests to use AD95xx (from AD9510 to AD9516), all of them are clock distributors except AD9516. So since I'm not experienced, I was wondering what they expect us to put as clock input, and why they don't suggest clock generators which seem to be more HF/low noise friendly !


Reply Children
  • 0
    •  Analog Employees 
    on Jun 23, 2021 12:15 PM in reply to Rleduc


    the AD9250 data sheet speaks about PECL "drivers". The clocking ICs they mention can output clocks with PECL characteristics.

    For many of these chips you have to use a crystal oscillator as the clock source.

    But if you want to use a crystal resonator, then look at the AD9520, AD9522 families.