• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 22 subscribers
  • Views 950 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2594: phase relation between SYSREF output and SysRefReq

ldx dfdx
Intellectual 400 points
Part Number: LMX2594


SysRefReq will be re-clocked by finterpolator，finterpolator is divided from VCO out. It seems that sysref output will have several possible phase . So there is no deterministic phase relation between  SysRefReq and SYSREF output?

  • 0
    TI__Expert 8505 points
    Hi Idx,

    For SYSREF modes, SYNC will be required (VCO_PHASE_SYNC=1), which serves the purpose to synchronize the dividers and achieve the deterministic phases.

    Regards,

    Brian Wang
  • 0 in reply to Brian Wang
    Intellectual 400 points

    Dear Brian,

          THanks for your quick reply!

          SYNC mode means part of the channel divider is in the feedback path,but SYSREF_DIV_PRE and SYSREF_DIV  is outside of feedback path. So the 2 dividers is synchronized(reseted) by SYSREF_REQ? And so SYSREF_REQ should meet the setup and hold time of output clock?

         Best regards,

         Lxd

  • 0 in reply to ldx dfdx
    TI__Expert 8505 points
    Hi Lxd,

    Sorry I missed this one! SysRefReq should meet the setup and hold times of the OSCin clock. Then all the blocks in the path to RFoutA are timed in respect to an OSCin edge, and the SYSREF blocks (SYSREF_DIV_PRE and SYSREF_DIV) in the path to RFoutB are timed in respect to the same OSCin edge, and now you have a deterministic phase difference between your RFoutA signal and the SYSREF signal. In addition, this deterministic phase difference can be adjusted to place at certain locations in relation to RFoutA.

    Regards,

    Brian Wang
  • 0 in reply to Brian Wang
    Intellectual 400 points
    HI，
    Thanks for your replay.
    in lmx2594 datasheet 7.3.14.4, it says if using repeater mode,set up the pulse count if desired. I'am wondering using which register toset up the pulse count. There is a field called SYSREF_PULSE_CNT,but its discription is :number of pulse in pulse mode in master mode.Then in repeater mode，the number of pulse of SYSREF output is determined by the SysRefReq input？
  • 0 in reply to ldx dfdx
    TI__Guru** 110060 points
    Hi Ldx,

    Sorry for the confusion, in Repeater mode, you don't need to setup the pulse count. We will fix the datasheet accordingly.