LPCOMP current consumption

[alyssiarosewhite]

NCS 2.5.2

Toolchain 2.5.1

NRF52840

Hi,

I'm currently power profiling our custom board.  So far I've managed to get the current consumption quite low (6.5uA at 3V), but my one hiccup at the moment is enabling the LPCOMP.  It increases the consumption by around 17uA.  I can see in previous posts that other people have made the same observation (this one in particular). I was wondering if any changes were being made to NRF52840 in future revisions regarding pulling this in line with the NRF52832 in terms of current consumption.

Putting the system into SYSTEM OFF isn't an option for us as we need RAM retention but also wake on LPCOMP.

Any ideas are welcome.

Thank you

[Kazi Afroza Sultana]

Hello,

If I understand correctly, you want to use the low-power comparator as an analog wakeup source from System ON.

In System ON, the LPCOMP can generate separate events on rising and falling edges of a signal or sample the current state of the pin as being above or below the selected reference. This will induce more current. If you do not use the LPCMP, you need to disable this. But you want to use this as wakeup pin?

''I was wondering if any changes were being made to NRF52840 in future revisions regarding pulling this in line with the NRF52832 in terms of current consumption.''

I have asked internally. I will get back to you lately.

Thanks.

BR

Kazi

[alyssiarosewhite]

Hi Kazi,

I suppose the LPCOMP is already working as a wakeup source from System ON in my project because the main thread sleeps until an LPCOMP event occurs.  I've read in other forum posts about this particular question that LPCOMP wakeup from System OFF is the only way to access the ultra low power side of the LPCOMP.  This is not an option for us because we need RAM retention and the datasheet has LPCOMP wakeup from System OFF with no RAM retention.

I do use LPCOMP, I'm just trying to get the overall average consumption down because that's the last peripheral that is bringing current consumption up.

Thank you for asking internally regarding, I await your response.

Alyssia

[Kazi Afroza Sultana]

Hello,

This is a HW limitation and it has not changed in later versions of nRF52840. The power domain required to keep LPCOMP enabled in SystemON is much larger than in nRF52832, causing the increased current. LPCOMP is primarily designed for use in System OFF.

So, you cannot keep the system ON and simultaneously keeping LPCOMP on to get desired current consumption.

What are the latency requirements?

[alyssiarosewhite]

Hi Kazi,

Okay so the previous statements from 6+ years ago still stand, thank you for checking.

My problem with System OFF is that there doesn't seem to be an option to keep RAM retention and also wake on LPCOMP.