43.2. PLLCTL SPREAD SPECTRUM

43.2.1. Overview

This example demonstrates the configuration spread spectrum of the Phase-Locked Loop (PLL) controller.

Spread Spectrum Capabilities

Implements spread spectrum modulation for EMI (Electromagnetic Interference) reduction with configurable parameters:

  • Spread Range

    • Default: 0.5%

    • Configurable through SS_RANGE macro

    • Adjustable range: 0.1% to 3.1%

  • Modulation Frequency

    • Default: 30 kHz

    • Customizable via MODULATION_FREQ macro

  • Spread Spectrum Type

    • Default: Downspread modulation

    • Configurable through PLLCTL_SS_TYPE macro

When the spread spectrum is enabled, on oscilloscope, similar FFT result is expected to be observed as following:

../../../../_images/pllctl_ss.png

For comparison, the FFT result observed on the oscilloscope without spread spectrum enabled is shown below:

../../../../_images/pllctl_no_ss.png

43.2.2. Board Setting

  • The configured PLL frequency can be observed via clk_ref* pin by the oscilloscope, please refer to Pin Description for pin information of specific board.

43.2.3. Running the example

When the project runs correctly, the serial port terminal will output the following information:

PLLCTL spread spectrum example
PLL0CLK0 @ 80000000Mhz ss has been enabled (downspread) with range 0.5% @ 30000Hz, which can be observed on "P2[16]" pin by the oscilloscope

PLLCTL example finished