Current consumption >1 mA changing LFCLKSRC

[Frederic]

Hello,

in my application i use a bootloader for S310 and S310 V2.1.0.

The Bootloader is configured to use NRF_CLOCK_LFCLKSRC_RC_250_PPM_4000MS_CALIBRATION and the application use NRF_CLOCK_LFCLKSRC_XTAL_20_PPM. I could now observe the following behavior:

1. I programm a application with DFU --> Application starts --> Current consumption < 100 uA
2. Start Bootloader from application --> wait 2 min (do nocthing) --> Application starts --> Current consumption < 100 uA
3. Power on cycle --> Application starts --> Current consumption > 1 mA

If i change the LFCLKSRC from the booloader to NRF_CLOCK_LFCLKSRC_XTAL_20_PPM and do a power on cycle the current consumption is < 100 uA, as expected.

Can't i use different LFCLKSRC?

[Frederic]

In documentation i found the following description:

@note Some care must be taken if a low frequency clock source is already running when calling this function: If the LF clock has a different source then the one currently running, it will be stopped. Then, the new clock source will be started.

@param clock_source Low frequency clock source and accuracy. (Note: In the case of XTAL source, the PPM accuracy of the chosen clock source must be greater than or equal to the actual characteristics of your XTAL clock).

But why the current consumption only increase if i do a power on cycle? Can i stop the LFCLK manually before call SOFTDEVICE_HANDLER_INIT(...)?

[Hung Bui]

Hi Frederic,

It's a bug we found in S110 v7.x and earlier. The bug is fixed and documented in our S110 v8.0 release note.

If you want to continue to use S110 v7.x and earlier, the work around is to call

NRF_POWER->TASKS_LOWPWR = 1;

after you disable the softdevice in the bootloader or before you start the softdevice in the application.

[Frederic]

ok, thank you i will try this solution. At the moment i use the lastest version from S310 V2.0.1. So i think there is no S310 availbale with bugfix.

[Hung Bui]

@Frederic: No it's not fixed on the S310. But the same workaround can be used for S310.

[Frederic]

Thanks for help, works great :-)