• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 21 subscribers
  • Views 281 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: SYSREF Delay Units

Richard Zarr
Expert 3040 points
Part Number: LMX2594

From the LMX2594 datasheet, Table 19: SysRef Delay, on sheet 36.

For the first column in the table, what are the units? Is this the number of sysref delay counts in picoseconds?

Also, the datasheet says the sum of JESD_DAC1 – JESD_DAC4 should always equal 63. But, there’s no explanation of how the integer values entered into JESD_DAC1 – JESD_DAC4 combine to produce a given “SYSREFPHASESHIFT” state.

Please help explain the entries in the table. If “SYSREFPHASESHIFT = 0” the table says JESD_DAC1 = 36, JESD_DAC2 = 27, JESD_DAC3 = 0, and JESD_DAC4 = 0. So, what are the values of JESD_DAC1 – JESD_DAC4 for “SYSREFPHASESHIFT = 1”? How about for “SYSREFPHASESHIFT = 2”?

  • 0
    TI__Genius 11900 points

    Hello Richard,

    Each step of the SYSREFPHASESHIFT is on the order of 8 ps.

    The SYSREFPHASESHIFT is set by the 4 JESD_DACx_CTRL fields. The settings needed to set a particular phase shift can be calculated in TICSPro. When you change the SYSREF Delay Control you will also notice a change to the 4 grayed out numbers below  SYSREF Delay Control box, these are the settings needed to be programmed in the JESD_DACx_CTRL fields.

    You can enter the desired SYSREFPHASESHIFT in TICSPro and get the values for JESD_DACx_CTRL.

    Thanks,

    Vibhu