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LMK04828: analog delay configuration

Mia Ma
Intellectual 2295 points
Part Number: LMK04828
Other Parts Discussed in Thread: LMK04832

Tool/software:

Hi team,

While we are going through our LMK04828 analog delay function, there is some confusing items, pls help to review and clarify the right understanding.

There is a max analog delay frequency spec to be 1536MHz:

Besides, there is also another description in the detailed function introduction with the content: 25ps analog delay, and total 500ps analog delay range.

So how do we understand the two different description here? 

For our application requirement, a 2.5GHz clock would be used, could we still use the analog delay function？

Thanks

Best regards

Mia

  • 0
    TI__Mastermind 19001 points

    Hi Mia, 
    Analog delays are valid for frequencies up to 1536MHz only - if you're DCLKOUT is greater than this analog delay functionality is invalid. 
    25ps is the step size for analog delay. Enabling the analog delay feature automatically adds 500ps of delay + the added analog delay step value. 

    Best regards, 

    Vicente 

  • 0 in reply to vicente flores prado
    TI__Intellectual 2295 points

    Hi Vicente,

    Do you have any idea if this limitation will also be the HMC7044? Do we have any other part could support analog delay up to 2000MHz?

    Thanks

    Best regards

    Mia

  • 0 in reply to Mia Ma
    TI__Mastermind 19001 points

    Hi Mia, 
    I see plots in the HMC DS where they show analog delay step size vs different frequencies, so I don't think that's a limitation. 

    LMK04832 does have this same limitation unforunately. 
    Why is your SYSREF clk 2.5GHz? Most applications - SYSREF is very low frequencies hence the analog delays are used for fine phase adjustments. 

    Best regards, 

    Vicente 

  • 0 in reply to vicente flores prado
    TI__Intellectual 2295 points

    Hi Vicente

    In the datasheet, it seems the analog delay maximum frequency is the device clock limitation not the SYSREF clk.

    The application is Device clk at 2.5GHz.

    Pls help to correct me if I am in a wrong understanding.

    Thanks

    Best regards

    Mia 

  • 0 in reply to Mia Ma
    TI__Mastermind 19001 points

    Hi Mia, 

    LMK04828 does have the analog delays for the DCLKOUTx but 1536MHz CLKOUT is still the maximum frequency supported for analog delays to work. If customer required analog delays - please ensure CLKOUT frequency is less than this value. 

    On LMK04832 - analog delays are only supported for SYSREF outputs. 
    The purpose of this is to meet SETUP & HOLD time requirements on the Rx end. 

    Unfortunately, LMK04832 still suffers from this maximum frequency limitation. 

    Best regards,

    Vicente