Confirm that modulation is permitted
Spread-spectrum clocks deliberately modulate frequency to distribute spectral energy. Confirm receiver support and constraints on PLLs, sampling, synchronization and high-speed interfaces before selection.
Specify the modulation parameters
Identify center or down spreading, deviation, modulation rate and the meaning of nominal frequency. A nominal frequency alone does not establish compatibility with an existing design.
Layout and power still matter
Spread spectrum does not replace sound routing, return paths, termination and power design. If a spectral peak improves, also check system function, link performance and other frequency bands.
How to start the review
Share the existing clock, EMI test conditions, frequency bands of concern, receiver and allowed modulation. Screen for compatibility first and use system testing to determine whether the target is achieved.
Project checklist
- Receiver spread-spectrum support
- Spread direction, deviation and rate
- Frequency bands and test conditions
- Functional and EMC retest plan