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LMK61E07: I2C communication interfered with clock output

Prodigy 90 points

Replies: 11

Views: 1182

Part Number: LMK61E07

Hi there,

I've noticed that the phase noise of the LMK61E07 is not as good as it was when I2C operations taken place.

I've tried periodically sending commands to change the LMK61E07 frequency or sending command just to read the product ID, or sending non-I2C PRN data to the I2C ports on the chip.

All the above three significantly worsen the phase noise of the LMK61E07 at the sideband related to the I2C port's communication.

Please see the following figure attached.

Thanks.

Regards,

Wade

  • In reply to Weida Zhang:

    Based on your config above, it looks like...
    You are using LVDS instead of LVPECL, and the PLL settings are what I produced with the LMK61E2 GUI.  Particularly using a different VCO frequency, fractional mode, and 1.6 mA instead of 6.4 mA.

    Please try this configuration attached, registers for reference:

    R0    0x0010
    R1    0x010B
    R2    0x0233
    R8    0x08B0
    R9    0x0901
    R16    0x1000
    R17    0x1180
    R21    0x1501
    R22    0x1600
    R23    0x1728
    R25    0x1900
    R26    0x1A32
    R27    0x1B00
    R28    0x1C00
    R29    0x1D00
    R30    0x1E00
    R31    0x1F00
    R32    0x2001
    R33    0x210C
    R34    0x2228
    R35    0x2303
    R36    0x2408
    R37    0x2500
    R38    0x2600
    R39    0x2700
    R47    0x2F00
    R48    0x3000
    R49    0x3110
    R50    0x3200
    R51    0x3300
    R52    0x3400
    R53    0x3500
    R56    0x3800
    R72    0x4802

    LMK61E2_125.tcs

    ____________________________________________________________________________________

    More information Clock and Timing System products: http://www.ti.com/clock-and-timing/overview.html

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