How do I disable the external LFXO and use an internal RC oscillator instead?

[tylerh]

Hi,

I'm running the system_off/ sample on v3.2.3 with these settings in prj.conf

CONFIG_PM_DEVICE=y
CONFIG_GPIO=y
CONFIG_CRC=y
CONFIG_POWEROFF=y
CONFIG_HWINFO=y
CONFIG_CLOCK_CONTROL_NRF=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=n
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y

And with this overlay file:

nrf54lm20dk_nrf54lm20a_cpuapp.overlay

However, I can see that there's a high (and in fact, higher than using the external crystal) power usage.

Are these settings correct for enabling the RC oscillator?

I'm following this page, and I'm trying to use the LFRC: docs.nordicsemi.com/.../clock.html

[SwRa]

HI Tyler,

Note that in nRF54LM20, LFRC cannot run in system off mode. LFXO can run in System OFF mode. The other clock sources only run in System ON mode.

Refer: https://docs.nordicsemi.com/bundle/ps_nrf54LM20A/page/clock.html#ariaid-title3 

Best Regards,

Swathy

[tylerh]

Thank you, that makes sense.

If I use another sample that doesn't directly go into System OFF, does that mean that the above configurations are sufficient to use the LFRC while in System ON mode?

[SwRa]

Hi Tyler,

Yes, for System ON mode only use cases, your configurations should be sufficient. The correct configurations needed are discussed in the following thread:  nRF54L DK - ESB Sample LF Clock Source Configuration Issue  

Regards,

Swathy