Intel® MAX® 10 Clocking and PLL User Guide

ID 683047
Date 12/26/2023
Public
Document Table of Contents

3.3.5. Guideline: PLL Cascading

Consider the following guidelines when cascading PLLs:

  • Set the primary PLL to low bandwidth to help filter jitter. Set the secondary PLL to high bandwidth to track the jitter from the primary PLL. You can view the Intel® Quartus® Prime software compilation report file to ensure the PLL bandwidth ranges do not overlap. If the bandwidth ranges overlap, jitter peaking can occur in the cascaded PLL scheme.
    Note: You can get an estimate of the PLL deterministic jitter and static phase error (SPE) by using the Timing Analyzer in the Intel® Quartus® Prime software. Use the SDC command derive_clock_uncertainty to generate a report titled PLLJ_PLLSPE_INFO.txt in your project directory. Then, use set_clock_uncertainty command to add jitter and SPE values to your clock constraints.
  • Keep the secondary PLL in a reset state until the primary PLL has locked to ensure the phase settings are correct on the secondary PLL.
  • You cannot connect any of the inclk ports of any PLLs in a cascaded scheme to the clock outputs from PLLs in the cascaded scheme.