SNAA366 October   2022 LMX1204

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 Basic Clock Distribution System
    2. 1.2 Pre-multiplier Stage
  4. 2Low-Frequency Reference
    1. 2.1 Pre-multiplier Stage
    2. 2.2 LMX1204 Multiplier Stage
    3. 2.3 LMX1204 Multiplier vs RF Synthesizer
  5. 3Real-World Application With AFE7950 RF Sampling Transceiver
    1. 3.1 AFE7950 Clocking Measurement Setup
    2. 3.2 AFE7950 Clocking Measurement Results
  6. 4Conclusion

4 Conclusion

The LMX1204 is a good clock distribution device designed to disseminate a high-frequency, low phase-noise clock to a large array of data converter devices. Designers can cascade multiple layers of the LMX1204 to generate as many outputs for the system as needed. Use the internal multiplier feature of the LMX1204 to take a high-quality, low-frequency reference source to generate the required high-frequency sample clock. This approach eliminates the need for a dedicated high-frequency synthesizer. Performance is shown to be better than operation with the integrated PLL/VCO of the device. Given that systems already have a low-frequency reference and already need to distribute the clocks, this approach requires minimal extra devices. Further, for critical radar systems utilizing Doppler shifts where close-in phase-noise performance is critical, the multiplier approach yields better close-in performance compared to a standard synthesizer with equally good reference.