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LMX2615-SP: Device synchronization

Gregory Duperon
Expert 6050 points
Part Number: LMX2615-SP

I have a customer planning to use the LMX2615-SP in an application.  They have a question regarding synchronization.

I would like to use the “Synchronization” feature by using the “SYNCH” Pin for all eight devices. Our “Fosc” is about 600MHz and I was wondering if I take the “Fosc” frequency to an FPGA and use the “Fosc” Clock to create “SYNC” pulses for all my devices. Will this work?

According to Table 13 of the datasheet the max “Fosc” says 40MHz.

  • 0
    TI__Mastermind 18070 points
    Hi Gregory,

    Please follow the datasheet and use 40MHz for category 3 of SYNC.

    Also make sure to check out figure 26 and see if category 3 is really needed. The 40MHz constraint does not apply to category 2 or 1.

    Yes user can use FPGA to generate SYNC pulse that is phase correlated with Fosc. Make sure that the setup and hold time for SYNC pulse is met.

    Regards,
    Hao
  • 0 in reply to Hao Z
    TI__Expert 6050 points
    Hao,

    Thanks.

    Here's a follow-up question:

    Regarding OSCinP/M input: if 8dBm sine wave is provided and the device is powered off, will it damage the part?

    Greg
  • 0 in reply to Gregory Duperon
    TI__Mastermind 18070 points

    Hi Greg,

    Please make sure that the input voltage swing does not violate datasheet:

    2.1Vpp will translate to 7.4dBm for 100Ohm differential, if my calculation was correct.

    We think it's okay to apply input when device is powered off but we need to double check with the validation and design team. I'll get back to you when I have the answer.

    Regards,

    Hao

  • 0 in reply to Hao Z
    TI__Expert 6050 points
    Hi Hao,

    Any update from the design team regarding this?

    In addition, for CAT 3, is 40MHz the max one should use?

    Thanks.

    Greg
  • 0 in reply to Gregory Duperon
    TI__Mastermind 18070 points
    Hi Greg,

    Designer said that if power supply is removed, then both single ended and differential OSCin can be used. If power supply is on, but the device is powered off using CE pin or powerdown bit, then only differential OSCin can be applied because single-ended will stress the driver and is not recommended.

    Regards,
    Hao