SDAA607 November   2026 LMX2581

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Hardware Design
  6. 3Loop Filter Components Selection
    1. 3.1 Design Example
    2. 3.2 Simulation in TI PLLatinum Sim
    3. 3.3 Test Verification
      1. 3.3.1 Setup
      2. 3.3.2 Test Results
  7. 4References

3.3.1 Setup

Typical test equipment for phase noise and jitter is Agilent E5052 and R&S FSPW. Figure 3-3 shows the preferred way to measure differential output phase noise for signals below 1GHz.

  • Differential output: rejects common mode noise and provides a bigger signal swing.
  • Balun: converts differential signals to single ended output to interface with the analyzer.
  • AC-coupled, or so-called DC blocker: blocks any DC signal going into the equipment and prevents instrument damage. RF Instruments do not accept DC.
LMX2581 Differential Clocking Test Setup Figure 3-3 Differential Clocking Test Setup

However, for signals higher than 1GHz, balun is not required. Single-ended measurement is sufficient.