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Original question:

LMK04828: OPT_REG_1 / OPT_REG_2 values with VCO0

LMK04828: OPT_REG_2 value

Piet Du Toit
Intellectual 370 points
Part Number: LMK04828

Tool/software:

Hi Derek 

I have a related question to the OPT_REG_2 value of the LMK04828.
The datasheet states a fixed value of 51 (0x33), but the DAC3XJ8X GUI V1.3 software populates a value of 15 (0x0F) in the config file.

Which value should be used?

Kind regards

Piet

  • +1
    TI__Mastermind 33530 points

    Use the datasheet value if you have the option.

    OPT_REG_1 and OPT_REG_2 are the VCO temperature compensation (OPT_REG_1) and amplitude calibration (OPT_REG_2) settings for VCO1 (the 2920 to 3080 VCO). Setting OPT_REG_2 to 0x0F, in particular, tends to pick the lowest VCO driver currents during calibration, which actually can take a few dB away from the phase noise performance when using VCO1. We should bring this to the attention of the DAC3XJ8X GUI owners, as well - it would be helpful if the GUI software used the recommended settings.