Entry of VLPS mode and necessity to disable SOSC, FIRC and SPLL

[Joey_van_Hummel]

Hi,

AN5425 and Ref.Man. Both mention that when entering VLPS, FIRC, SOSC and SPLL should be disabled. SIRC should be the system clock. Coming from the S12, where entering STOP automatically switches off the PLL, I initially simply entered VLPS without switching to SIRC. After wake-up, PLL automatically became active again and the system works as expected.

I now switch to SIRC before entering VLPS but do not see difference in functionality or power consumption. So just out of curiosity: why is this necessary?

For reference, I am talking about section 5.5.2 of AN5425 and section 27.4.4 of S32K-RM v12.1.

Kind regards, Joey

[danielmartynek · Accepted solution]

Hi Joey.

FIRC, SOSC and SPLL should be disabled by the SW - it is not guaranteed that it gets automatically disabled during the transition.

In general, if the MCU is used out of the specifications, the functionality is not guaranteed.

Regards,

Daniel

[Joey_van_Hummel]

Hi Daniel,

I see. This is a notable difference between the S12, which guarantees this, and the S32.

Thanks for your reply.

Kind regards,

Joey