SPRADK1 September   2025 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP , AM62A1-Q1 , AM62A3 , AM62A3-Q1 , AM62A7 , AM62A7-Q1 , AM62L , AM62P , AM62P-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Spread-Spectrum Clocking
    1. 1.1 SSC Modulation Rate
    2. 1.2 SSC Modulation Depth
    3. 1.3 SSC Spread Type
    4. 1.4 SSC Modulation Profile
  5. 2PLL SSC Implementation Details
    1. 2.1 PLL SSC Configuration Registers
    2. 2.2 PLL SSC Implementation Sequence With DSS PLL17 on AM62Px
  6. 3SSC Conclusion and Considerations

Abstract

Electrical interfaces that utilize high-frequency clocks to transmit and receive data radiate energy that can possibly interfere with nearby devices. This radiation is called Electromagnetic Interference (EMI). By making use of spread-spectrum clocking (SSC), EMI can be reduced to meet emission standards and regulations. SSC is a technique used to introduce controlled variation of the clock signal frequency to reduce EMI. When implementing SSC, EMI is distributed across a wider frequency range instead of concentrating solely at the nominal clock frequency. Care must be taken to modulate the clock within the tolerance of the overall system to avoid disrupting communication between the circuits and devices involved.

This document describes how EMI reduction is achieved when using the Display Parallel Interface (DPI) with a 24-bit RGB data output to modulate the pixel clock frequency using SSC. The method applies to AM62x, AM62Ax, AM62Px, and AM62Lx system-on-chip (SoC) designs.