nRF52 LFCLK ~40 uA consumption with SRC=Xtal

RE: nRF52 LFCLK ~40 uA consumption with SRC=Xtal

damaki — Mon, 17 Sep 2018 13:33:24 GMT

Hi Stian,

Thanks for testing these on your end. It's good to know that with a power analyzer the current consumption meets my original expectation.

I'll get a newer version of the DK for performing current measurements.

RE: nRF52 LFCLK ~40 uA consumption with SRC=Xtal

Stian Røed Hafskjold — Mon, 17 Sep 2018 12:42:32 GMT

I tried measuring both of the hex files on a Preview DK with the eng. A chip revision as you are referring to. With a Power analyzer I got 3-4 µA on both the hex files you sent. And with the PPK I got 44 uA on both hex files.

I recommend you to get a newer version of the DK. The DK version corresponding to QIAAAA (eng A) was the first version released and it was not very stable. Not really sure where the 40 µA comes from but this is not related to LFXO vs LFRC.

RE: nRF52 LFCLK ~40 uA consumption with SRC=Xtal

damaki — Tue, 11 Sep 2018 11:13:47 GMT

Hi Stian,

Thanks for the reply and suggestion.

I am already checking the that the LFCLK is starting before using the RTC with the same code you posted (start the LFCLK, wait for it to start, then clear the event). I have also confirmed that the LFCLK is starting correctly and with the correct source by inspecting the CLOCK registers via a debugger once the code has started.

I've attached the two hex files using the LFRC or LFXO clock source. I built these by only changing the line of code which sets the LFCLKSRC register. The attached programs should both blink LED2 with a period of 500 ms on, 500 ms off.

devzone.nordicsemi.com/.../blinky_5F00_lfrc.hex devzone.nordicsemi.com/.../blinky_5F00_lfxo.hex

RE: nRF52 LFCLK ~40 uA consumption with SRC=Xtal

Stian Røed Hafskjold — Tue, 11 Sep 2018 10:12:48 GMT

Did you add any checks to determine that the LF crystal is actually starting up? It needs to start up before you can enable the RTC. Something like this:

NRF_CLOCK->TASKS_LFCLKSTART = 1;
while(NRF_CLOCK->EVENTS_LFCLKSTARTED == 0){}
NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;

If this is not working, can you please post the hex file here, both the LFXO and the LFRC one. Then I can try to measure here on a preview DK.

RE: nRF52 LFCLK ~40 uA consumption with SRC=Xtal

damaki — Mon, 10 Sep 2018 14:28:40 GMT

Some additional information:

The chip marking is: N52840 Q1AAAA 1716AK

I perform the same errata workarounds in my startup code from system_nrf52840.c in the nRF5 SDK. I.e the workarounds for erratas 36, 66, 98, 103, 115, 120, and 136.