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LMK04828: LMK04828 MultiBoard synchronization using CLkin0

SAI PADMINI
Prodigy 10 points

Part Number: LMK04828

Tool/software:

Hi,

We are Having two RFSoC boards with LMK04828B in each one of them to generate the required clocks for the ADC/DACs.

We are looking to synchronize the two LMK chips using a single reference clock of 5 MHz on to the CLKIN0

LMK1: (RFSoC Board 1)

Oscin : 100 MHz (On Board VCXO)

Clkin0 : 6.25 MHz (Reference from Master Board)

Clkin1, Clkin2 : Not connected

DCLKout : 312.5 MHz

SDCLKout : 6.25 MHz Pulsed mode

LMK2: (RFSoC Board 2)

Oscin : 100 MHz (On Board VCXO)

Clkin0 : 6.25 MHz (Reference from Master Board)

Clkin1, Clkin2 : Not connected

DCLKout : 312.5 MHz

SDCLKout : 6.25 MHz Pulsed mode

The DCLKout and SDCLKout of two boards need to be phase synchronized. Can we synchronize the two LMK's simply by using a single reference of 6.25 MHz to the CLKIN0. ? If yes can you explain the synchronization sequence for the same.

Thankyou

Regards

SAI

Regards

  • 0
    TI__Expert 8421 points

    SAI,

    Sorry for the delay.  Yes this is definitely feasible.  In order to synchronize two LMK04828 board outputs you must use Zero Delay Mode to set a deterministic relationship between your input and your output.  In order to synchronize all of your outputs you need to send a SYNC pulse to reset the output dividers to synchronize each of the outputs to each other.  There is a good app note here that goes into further detail. Let me know if you have further questions.  

    Regards,

    Will

  • 0 in reply to William Pfennigwerth
    Prodigy 10 points

    Hello William,

    Thank you for the response. I have gone through the app note attached for the multi board LMK sync.

    I have configured both the boards in ZDM, each board is using its own independent 100 MHz VCXO.

    1) 6.25 MHz signal is fed to CLKin0 of both the boards from an external source. This is used as reference for the PLL1.

    2) Once Both the boards are locked, A common sync pulse is sent to both the boards which is used for resetting the dividers.

    3) After the above steps, i could see the SDCLKout signals of both the boards getting aligned, but the DCLKout of two boards are not synchronized.

    Am i missing any additional synchronization step. I have attached the .tcs file i have used. Please review and give your feedback.ZDM_LMK04828B.tcs

    Regards

    SAI

  • 0 in reply to SAI PADMINI
    TI__Expert 8421 points

    SAI,

    Yes.  Now that your SYSREF signals are synchronized you can synchronize all of your outputs by correctly adjusting the fixed digital delay.  Once you have correct digital delay the common sync should synchronize all your outputs.  You can read about how to set this up in Section 9.3.3.1 in the datasheet.

    Regards,

    Will