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


The LMX1204 is a high-performance clock distribution device. This device is intended to distribute a low phase-noise clock or local oscillator (LO) signal across many channels. The device also employs an integrated multiplier operating between 3.2- and 6.4-GHz output. Designers can use the multiplier feature to create a high-frequency signal from a low-frequency reference source and then distribute as needed. This approach eliminates the need for a separate radio-frequency (RF) synthesizer to generate the signal and the additional power dissipation of such a device. This note presents the phase-noise performance of the multiplier feature in the LMX1204 compared to industry test equipment to gauge the relative performance of the LMX1204. The final test uses the multiplied-up reference from a cascaded LMX1204 design to drive the external clock of the AFE7950 RF sampling transceiver and compare performance of the design to the internal phase-locked loop (PLL) plus voltage-controlled oscillator (VCO) of that device.