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STM32L476 MSI + PLL

Question asked by Juha Aaltonen on Oct 13, 2017
Latest reply on Oct 21, 2017 by Clive One

What is the magic that PLL doesn't want to let go of MSI?

I've been trying to switch MSI + PLL ON/OFF during STOP2 mode (to save battery), but the MSI + PLL hangs on for about 15 milliseconds. I'm first switching onto HSI16 to "free" PLL and then turning OFF the PLL and then setting PLL clock source to NONE. I've also tried turning the SAI1 and SAI2 PLLs off before disabling the main PLL, but that didn't seem to be the problem. Also going to STOP2  with PLL left ON seems to make it hard to get the MSI + PLL started after wakeup.

 

The PLL comes off from HSE normally.

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