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LMK04832: LMK04832 output continuous SYSREF signal

APPLO ZHANG
Intellectual 515 points
Part Number: LMK04832


  

It is very strange why the configuration on the left can output a continuous SYSREF signal. The picture on the right is the functional block diagram of the tics-pro software, the toggling signal is not connected to the sysref signal source.

Thanks!

   

  • 0
    TI__Mastermind 18930 points

    Hi Applo,

    On the bottom of software block diagram, I see that the green "Continuous" path comes from the "SYSREF Digital Delay/Clock Divider" block, which comes from either VCO1, VCO2, or CLK1in. So my guess is that the continuous SYSREF does not come from the SYNC pin. We have contacted a device expert who can confirm this.

    Thanks,

    Evan Su

  • 0 in reply to Evan Su
    Intellectual 515 points 
    Thank you for your prompt reply. My understanding is that, as you said, 
    the green "Continuous" path comes from the "SYSREF Digital Delay/Clock Divider" block, 
    which comes from either VCO1, VCO2, or CLK1in    , but to make it output requires an enable signal,
    and I don’t know where the enable signal comes from?
  • 0 in reply to APPLO ZHANG
    TI__Genius 12560 points

    Hi Applo,

    As soon as you set the SYSREF_MUX for SYSREF Continuous (0x139 --> 03), it will generate the continuous signal irrespective of SYNC_mode settings. 

    To generate the SYSREF pulses, change SYSREF_MUX to Pulser (0x139 --> 02) then pulses will be generated through SYNC pol.

    Thanks!

    Regards,
    Ajeet Pal

  • 0 in reply to Ajeet Pal
    Intellectual 515 points

    【As soon as you set the SYSREF_MUX for SYSREF Continuous (0x139 --> 03), it will generate the continuous signal irrespective of SYNC_mode settings. 】

    Looking at the datasheet also needs to enable the output of continuous Sysref: 

    But SYSREF_REQ_EN = 0, the toggling signal is not connected to the sysref signal source.

  • 0 in reply to APPLO ZHANG
    TI__Mastermind 18930 points

    Hi Applo,

    That section of that data sheet ("Now asserting the SYNC pin...") is an example of running in pulser mode so it needs a signal from SYNC to trigger the pulse train. If you manually set SYSREF_MUX to SYSREF Continuous then there should not be any need for any toggling signal because it will always be on.

    Best,

    Evan Su