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LMK04803 and clock tool question

Other Parts Discussed in Thread: LMK04803, LMK04906, LMK04806, CODELOADER

Hi,

I had 3 questions from my customer as below. Could you support them?

Q1) My customer has been using "CoreLoader" to confirm the register settings of LMK04803.

But the customer cannot set "1" to both "Doubler" and "R Counter" at the same time..

Could you tell me the reason why we cannot set "1"?

For example, although we try to be 10MHz clock as ref-signal by using input 10MHz, we can only set both "2", not "1".

 
I have guessed the reason is from the LMK04800 datasheet description "7.6.2.1 PLL2 FREQUENCY DOUBLER", due to we can minimize the noise by setting "2"... Is my idea correct?

Q2) About the noise, which frequency is better to use for the input signal to minimize the noise, "higher frequency input" or "lower one"?

Q3) The influence of "thermal"

It seems to be easily getting the influence of thermal when the customer is measuring the device.

Could you please advise me how to do to reduce the influence, e.g. should use "cooling fan" or should use something "heat sink"?   

Thank you for your support in advance.

Best Regards,

 

 

    


  
  
  
  
  
  
  
  
  
  
  
 
 
 


 

  • Hi Takumi-San,

    1) For applications in which the OSCin frequency and PLL2 phase detector frequency are equal, the best PLL2 in-band noise can be achieved when the doubler is enabled and the PLL2  R divide value is 2. Do not use doubler disabled and PLL2 R divie value of 1. This is a workaround required for this silicon. The note is included in the LMK04906 datasheet but we apologize that it has not been documented clearly in the LMK04806 datasheet.

    2) Higher reference frequency resulting in higher phase detector update rate is preferred (as long as the max Phase Detector Rate is not violated). Doubling the phase detector frequency will result in 3 dB improvement in the in-band phase noise

    3) What is the customer's I/O configuration (Codeloader .mac file) and power budget? Also if the outputs are configured LVPECL, can they update those to LVDS to minimize power?

    Regards

    Arvind Sridhar

  • Arvind-san,

    Thank you very much for your reply.

    Let me ask you some questions again as below.

    1) What is the defference between LMK04806 and LMK04906?

        Is it better to propose LMK04906 to the customer?

       And following description is what you are pointing me, right?

     I will confirm the customer's configuration and get back it to you soon.

    Best Regards,

  • Arvind-san,

    Sorry one more question, please.

    About cooling of the device, "Fan+Heat sink" is the best solution.

    But if the customer cannot do both, what is the condition(power budget) to select Fan or heat sink? 

    Thank you in advance!

  • Hi Suzuki-San,

    LMK04906 is a basically a subset device of LMK04806. The VCO operating range is similar. LMK04906 has 6 outputs instead of 12 on LMK04806. They are not pinout compatible and LMK04906 is better optimized for crosstalk. Also, the LMK04906 supports 3 redundant inputs vs 2 on LMK04806. Depending on what the customer desires (more outputs, more redundant inputs etc), the choice can be made between LMK04806 Vs LMK04906.

    Regards

    Arvind Sridhar

  • Hi Suzuki-San,

    Per my earlier reply (copied below), the power dissipated from the device depends on the customer's configuration.

    What is the customer's I/O configuration (Codeloader .mac file) and power budget? Also if the outputs are configured LVPECL, can they update those to LVDS to minimize power?

    Regards

    Arvind Sridhar

  • Hi Arvind-san,

    I see, I am asking the customer to provide the information.

    Let me inform you after getting it.

    Best Regards,

  • Arvind-san,

    Thank you very much for your explanation.

    I understood.

    Best Regards,