NRF52840 Low Power with External Oscillator Running

[Greg Nowak]

I'm using a BMD-340 with the NRF52840.    I'm using the 32.768 kHz oscillator to provide the clock to an external real time clock.

The snippet of the schematic is below.   When in normal power on state everything works fine, CLK_32768 is as expected.

I need to be able to get the NRF52840 into as low a power state as possible but keep this oscillator running to maintain the real time clock on the other chip. 

My first attempt was just going into "power down" mode, but that shuts off this oscillator.  

Is there a way I can configure the NRF52840 to keep this oscillator alive but still go into a deep sleep or low power mode?  

I'm using NCS 2.3

[Jared]

Hi,

My first attempt was just going into "power down" mode, but that shuts off this oscillator.  

By power down mode, are you referring to System OFF or System On IDLE mode? In the former, all clocks will be stopped and it's not really possible to enable them in this mode,

regards

Jared 

[Greg Nowak]

Correct, I mean SYSTEM OFF.   I "fixed" it by just holding all of my tasks in a forever loop while in "powered down" state and I get close to the same current draw as I did in the system off state, so it's acceptable.