Best practice to poweroff an nrf52840 that's using BLE?

RE: Best practice to poweroff an nrf52840 that's using BLE?

ZebbleMan — Wed, 23 Apr 2025 15:41:02 GMT

I did start going down the debug route and wasn't getting anywhere with my code. So, I decided to try the peripheral_lbs demo code on the Xiao nrf52840, using the prj_minimal.conf. I added the sys_poweroff() after a k_msleep(5000) in the main loop and current dropped to 15uA. No other changes required!

So, I'm likely going to use peripheral_lbs as a base for my code. There's a lot of functionality already included that should simplify a lot of what I've already done.

At least I know this code works as its supposed to. Now I'll just add component-by-component and test power consumption as I go.

Thanks again for your help. I will post again if I run into another power consumption snag!

RE: Best practice to poweroff an nrf52840 that's using BLE?

ZebbleMan — Tue, 22 Apr 2025 18:24:35 GMT

Sorry for the delay in my response!

I'm going to dig into what you've outline. Hopefully some answers in the meantime to a couple of your questions:

- I'm using the PPK in power source mode, set to 3.3V.
- The module I'm using (Xiao nrf52840) does not include a PA/LNA.

I'll keep you posted on the outcome of your other recommendations.

Thanks again, much appreciated.

RE: Best practice to poweroff an nrf52840 that's using BLE?

Vidar Berg — Tue, 15 Apr 2025 13:34:21 GMT

Hello,

Sorry for the delayed response.

[quote user=""]Using a PPK and after a sys_poweroff(), the current draw floats around 550uA. This seemed very high so we started isolating what was drawing so much power. [/quote]

GPIO configurations are retained in System OFF mode. Therefore, when seeing higher than expected current in this state, it's usually due to a pin configuration issue or an external circuit. I suggest placing a breakpoint at sys_poweroff() and checking the GPIO registers to ensure all pin configurations are correct.

[quote user=""]Using just flash and some tweaks got the consumption down to 20uA @ 3.3V and ~7nA(!?) @ 3.0V[/quote]

It would be great if we could advertise a sleep current of only 7 nA, but that value is too low to be valid, unfortunately. Typical range is between .8 to 1.86 uA according the product specification (note: RAM retention in system OFF is not enabled by default). Are you using the PPK in ammeter or power source mode?

Ref. (https://docs.nordicsemi.com/bundle/ps_nrf52840/page/_tmp/nrf52840/autodita/CURRENT/parameters.i_sleep.html )

[quote user=""]

Re-adding bluetooth seemed to be the culprit and running some of the samples seem to have the same issue when adding sys_poweroff(). Everything still floats at around 500uA.

So, what's the best way to ensure bluetooth is not drawing current after sys_poweroff()?

[/quote]

It seems strange that enabling Bluetooth consistently leads to a higher system OFF current. Does your design include a front end module (PA/LNA) by any chance?

Best regards,

Vidar