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AFE7422EVM: Mode 7 - VCO Tuning

Preethika S
Prodigy 120 points

Part Number: AFE7422EVM

Dear Vijay/Team,

We are trying to configure AFE7422 in Mode 7.

Our Required configuration parameters include,

  • LMFSHd - 24410 (Mode 7)
  • Interpolation - 36x
  • Decimation - 12x
  • Required FRef - 153.6 MHz
  • Required DAC Sample Rate - 5529.6 Msps
  • Required ADC Sample Rate - 1843.2 Msps
  • DAC-to-ADC Ratio - 3.

We configured LMK04828 in AFE7422EVB to get 153.6 MHz as our Fref. LMK Locked.

But RF PLL/SERDES PLL is not locked. VCO is centered at 5898.24MHz. We need to fine tune the VCO to 5529.6 Msps.

We also tried to apply the following configuration using AFE74xx GUI.

Can you please suggest us possible way to tune VCO at 5529.6 MHz. Or Please provide cfg file to support the above mentioned parameters.

Thanks,

Preethika S

  • 0
    TI__Genius 14791 points

    Hi Preethika,

    In the datasheet section 7.3.4.2, Internal PLL/VCO Mode, has instructions on how to tune the VCO.

    To tune the VCO you will have to adjust the value of the PLL_VCO_IN register while monitoring the PLL_LFVOLT register. When the PLL_LFVOLT register reads back a value of 3 to 5 that means the VCO is tuned to the appropriate frequency. 

    Regards,

    David Chaparro

  • 0 in reply to David Chaparro
    TI__Genius 14791 points

    Hi Preethika,

    Also, to get the addresses for both PLL_VCO_IN and PLL_LFVOLT you can use the AFE74xx_Register_Set_slau798.pdf document.

    Regards,

    David Chaparro