• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 21 subscribers
  • Views 477 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

Original question:

LMX2572: RAMP GENARATION

LMX2572: Sub-Fractional Spurs

Koshi Ninomiya
Expert 5045 points
Part Number: LMX2572

Hi Team,

My customer is evaluating LMX2572 on their ES board, and they have a question about sub-fractional spurs.
When they evaluated the 2nd  ES board, sub-fractional spurs of LMX2572 became around 5dB higher than that of the 1st ES board.
They do not change application of LMX2572 and settings, they also use MASH_SEED with the same setting.
It is a general question,
Q1: Does the sub-fractional spurs vary by variation of LMX2572 characteristic, part to part, or lot to lot?

Thank you.

Best Regards,

Koshi Ninomiya

  • 0
    TI__Guru* 97920 points

    Hi Ninomiya-san,

    Do you have their configuration such as phase detector frequency, VCO frequency, etc?

  • 0 in reply to Noel Fung
    TI__Expert 5045 points

    Hi Fung-san,

    Their configuration is as follows,

    Option-1: 5523MHz_190315.txt

    5523MHz_190315.txt
    Fullscreen
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    R78 0x4E0001
    R75 0x4B0800
    R71 0x470081
    R57 0x390020
    R46 0x2E07F1
    R45 0x2DCE1E
    R44 0x2C3F23
    R43 0x2B0017
    R42 0x2A0000
    R41 0x290051
    R40 0x280000
    R39 0x270064
    R38 0x260000
    R37 0x258305
    R36 0x240037
    R34 0x220010
    R30 0x1E18A6
    R29 0x1D0000
    R14 0x0E1878
    R12 0x0C5001
    R11 0x0BB018
    R10 0x0A10F8
    R9 0x091004
    R0 0x00231C
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    Option-2:5629r25MHz_190315.txt

    5629r25MHz_190315.txt
    Fullscreen
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    R78 0x4E0001
    R75 0x4B0800
    R71 0x470081
    R57 0x390020
    R46 0x2E07F1
    R45 0x2DCE1E
    R44 0x2C3F23
    R43 0x2B0075
    R42 0x2A0000
    R41 0x290111
    R40 0x280000
    R39 0x270190
    R38 0x260000
    R37 0x258305
    R36 0x240038
    R34 0x220010
    R30 0x1E18A6
    R29 0x1D0000
    R14 0x0E1878
    R12 0x0C5001
    R11 0x0BB018
    R10 0x0A10F8
    R9 0x091004
    R0 0x00231C
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

    Thank you.

    Best Regards,

    Koshi Ninomiya

  • 0 in reply to Koshi Ninomiya
    TI__Guru* 97920 points

    Hi Ninomiya-san,

    in Option 1, are you referring to 1MHz and 500kHz spurs?

    In Option 2, 250kHz and 125kHz spurs?

    In both cases, you can set the fractional DEN to an irrational number such as 400001234 to eliminate these spurs.