How to enable Spread Spectrum for PLL1 on i.MX 8ULP

[ericnelsonaz]

Hi all,

Can anyone provide some guidance about how to enable Spread Spectrum for PLL1 on an i.MX8ULP.

It appears that PLL2 and PLL3 are enabled in late U-Boot SPL here, so we should be able to configure registers PLL2SS and PLL3SS prior to the initialization calls.

PLL1 appears to be enabled prior to U-Boot though, and I'm not sure where to update the PLL1SS register.

[ericnelsonaz]

Many thanks to Gary Bisson at EZurio for pointing me at the answer.

The MCUXpresso code for the M33 microcontroller has a routine for this (CLOCK_EnablePll1SpectrumModulation).

And as a bonus, there's also CLOCK_EnablePll4SpectrumModulation() for PLL4!