BC840 Low power current in System ON

RE: BC840 Low power current in System ON

user2111 — Thu, 02 Jun 2022 08:47:41 GMT

In situations like this I recommend to also get an nRF52840-DK to measure on in parallell, I believe most examples in zephyr should be pretty power optimized as long as you remove disbale CONFIG_SERIAL as you already do. You may something as simple as this for comparison:
https://devzone.nordicsemi.com/f/nordic-q-a/76231/nrf52840-zephyr-how-to-achieve-low-current-consumption

Kenneth

RE: BC840 Low power current in System ON

user116604 — Wed, 01 Jun 2022 23:46:12 GMT

I have configured only the GPIO I am using, so there should be none that are accidentally input floating. I assume the default state of IO is high-z and they should be left floating? I did try the finger test, but the footprint is BGA so it probably isn't of much help. I just audited all of the GPIO again and everything looks to be configured correctly.

Do you know if there is anything special I need to do in order to ensure the 32MHz external crystal is disabled during sleep? The technical reference says that power savings clock control is done automatically when nothing is using it, but perhaps it's not actually getting disabled. The shell command `nrf_clock_control` does show the HFCLK as being "off" when sleeping, but maybe there's a bug?

The current draw from the MCU is 250uA, since 20uA is the quiescent current of the PCB.

RE: BC840 Low power current in System ON

user2111 — Wed, 01 Jun 2022 11:56:50 GMT

I have not tried you code, but in general you may find this useful:
https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/optimizing-power-on-nrf52-designs

However the 270uA is a slightly odd value, have you tried moving your finger around the board and check if the current drastically changes? I am thinking it can be a floating input pin that cause excessive current, if that it the case then typically it will change if touched by a finger.

Kenneth