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LMK04828 122.88 MHz oscillator frequency, recommended oscillator to optimize the performance of the DAC3XJ8XEVM (DAC38J84 + TRF3722)

Kim Ber
Prodigy 120 points
Other Parts Discussed in Thread: DAC38J84, TRF3722, LMK04828

Why was the 122.88 MHz oscillator frequency chosen (as opposed to 100 MHz, 125 MHz, 200 MHz, etc.) for the DAC3XJ8XEVM?

If I want to operate the DAC38J84 at the sample rate of 2.46 GSPs or 2.5 GSPS is there a recommended frequency/phase noise for the PLL2 external clock reference in order for the LMK04828 to generate the clocks that will minimize the phase noise/jitter for both the DAC38J84 clock signal and the clock reference for the TRF3722?

  • 0
    TI__Mastermind 20900 points
    Hello Kim,

    122.88MHz is a typical frequency for wireless infrastructure, which is one of the target markets for the DAC38J84. But it is allowed to change the oscillator.
    For 2.5GSPS you could use a 125MHz oscillator. The PLL2 of LMK04828 is a clock generator only, therefore the oscillator phase noise should be very good to achieve best DAC performance.
    in case the reference clock is noisy, you can engage the first PLL of LMK04828 as a jittercleaner.

    regards,
    Julian