nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

RE: nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

Jørgen Holmefjord — Wed, 15 Jul 2020 14:45:57 GMT

As far as I know, there are no plans to "fix" this in nRF52840. You need to enter System OFF mode to get the low current consumption from the LPCOMP peripheral. In System ON mode, the power domain is active and will draw a higher current.

RE: nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

Prakash Rajiah — Wed, 15 Jul 2020 09:57:36 GMT

Hi Team,

Any update on this discussion.. I am still seeing 20uA on the system ON mode which is killing my battery .. When i remove

the nrf_drv_lpcomp_enable(), my system is coming down to 4.5uA..

Thanks

Prakash

RE: nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

Jørgen Holmefjord — Fri, 25 Jan 2019 15:27:49 GMT

The LPCOMP is still very low power in System OFF mode, which is where a lot of our customers use this peripheral.

I'm not able to comment on future products in this forum, but you can contact your regional sales manager if this feature is important for you.

RE: nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

jumpingfool — Thu, 24 Jan 2019 22:38:57 GMT

Pulse width is < 1ms so it is not viable for us to use continuous sampling via SAADC - we need the comparator.

This seems very odd, what's the point of having an LPCOMP on the chip if it's going to use almost as much power as the standard comparator? Having the LPCOMP peripheral onboard was one of the reasons we targeted the Nordic platform.

Any chance this may be improved in future revisions of the nRF52840?

RE: nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

Jørgen Holmefjord — Thu, 24 Jan 2019 19:08:59 GMT

In fact, the LPCOMP is the same, and its isolated run current is about the same in nRF52840 as in nRF52832. It is the power domain that is enabled with the LPCOMP in system on mode that is much bigger in nRF52840. Unfortunately, there is no workaround for this.

How long is the pulse you are detecting? If you do not need hig sample rate, you could look into using the SAADC in low power mode, and use limits to only trigger interrupts when you go below the threshold.

RE: nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

jumpingfool — Thu, 24 Jan 2019 10:34:30 GMT

Oh dear - that's not good if it is the case!

This is also at odds with advice given elsewhere, eg:

https://devzone.nordicsemi.com/f/nordic-q-a/41660/what-s-the-current-consumption-of-the-low-power-comparator-really/162306#162306

"The LPCOMP in the NRF52840 is identical to the one in the nRF52832, so iexpect it to be the same, i.e. LPCOMP electrical spec lists 0.5uA typical consumption to run the LPCOMP."

We use the LPCOMP to capture trigger events from a sensor. The LPCOMP is used rather than straight GPIO to allow us to calibrate the sensitivity of the sensor by adjusting the voltage at which we capture events. The system needs to be running (system on) as it is doing other things while waiting for events, e.g. maintaining a BLE connection.

This is going to significantly impact the battery life of our application - is there really no work around?

RE: nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

Jørgen Holmefjord — Thu, 24 Jan 2019 10:09:01 GMT

Hi,

The typical run current with LPCOMP enabled in nRF52840 is 20 µA. The difference from nRF52832 come from higher leakage current in nRF52840 when this peripheral is enabled. The current will be greatly reduced by putting the chip in System OFF sleep mode (~1 µA), if this could be an option for you.

What are you using the LPCOMP for in your design?

Best regards,
Jørgen

RE: nRF52840 Sleep, System-on, wake on LPCOMP - Unexpectedly High Power Consumption

Jørgen Holmefjord — Wed, 23 Jan 2019 14:19:40 GMT

Hi,

I'm checking this with our HW developers. I will get back to you as soon as I get an answer.

Best regards,
Jørgen