Current measurements NRF9160 DK

[isurki]

Dear Community;

I am running some current measurements on the NRF9160 DK. I am following the manual instructions:

1.-I am powering the NRF through external power supply pins with 3.6V.

2.-I slide switch 10 to EXT position.

3.-I connect a current meter to the two uppermost p24 pins.

Results:

In the current meter, I get negative values and then stabilizes at 4uA. If I put another current meter in series with the 3.6V Li-Ion battery the NRF is consuming 300uA.

I have seen that in the blog of "how to measure currents" it is necessary to cut SB43, but in my DK(0.8.3) it came already cut.

So I have two questions.

1.-What I am doing wrong to measure negative values and then 4uA when the real consumption value is 300uA?

2.-Why is the board consuming 300uA when I reach k_cpu_idle() if I have disabled config_serial in my project conf and SPM conf?

Any help is important due to is the final phase of a project and we need to achieve 20-50uA.

Thanks in advance.

[Marjeris Romero]

Hi,

1. How much negative current are you measuring and how long does it take to stabilize at 4 uA. Some negative current during peak time can be expected because of the circuits capacitance.

2. How are you connecting the Li-Ion battery? If you connect the battery to the external supply header you will measure the current going into the Segger programmer chip and everything else in the DK.Current measurement from the current measurement header P24 shows only the current that is used by the nRF91 chip.

BR,

Marjeris

[isurki]

Hi;

Thanks for your answer!

1.-I get negative current values from 60 to 25uA until it stabilizes at +4uA after 3 seconds approximately.

2.-I am connecting the Li-Ion battery to the P28 connector. How can I power the board to avoid Segger programmer chip and everything else extra consumption? I only want to power the NRF9160.

Kind regards.

[Marjeris Romero]

Hi,

The negative values at the start of a measurement are common if you have inductive/capacitive load, the important thing is the average current you measure when it's stabilized.

I am not sure if you can power only the nRF91 chip when using P28. There is a switch for disconnecting the interface MCU (SW6) but you still will be powering the rest of the board, so for accurate measurements I recommend measuring using header P24 as described in the documentation. Take a look at this blogpost for more information.

BR,

Marjeris

[isurki]

Hi;

Marjeris Romero said:

I am not sure if you can power only the nRF91 chip when using P28

And is it possible to only power the nRF91 chip using P15 pins?

Marjeris Romero said:

here is a switch for disconnecting the interface MCU (SW6)

Do you refer to SW1 ("nRF only" switch)? It seems that SW6 is for testing digital inputs.

Can we achieve a lower power consumption disconnecting a solder bridge(SB13 for LDO for example)? 

The aim is to achieve low power consumption of all DK, not for the nRF91 only.

Thanks for you help,

Kind regards.

[Marjeris Romero]

Hi,

P15 is used for the current measurements using the PPK. The firsts pins are the same as the ones in P24 and the rest are SWD.

isurki said:

Do you refer to SW1 ("nRF only" switch)? It seems that SW6 is for testing digital inputs.

Yes, it seems the switch's name was changed to SW1 in some later versions of the DK. See "IFMCU DISCONN" switch in the hardware figures here.

isurki said:

The aim is to achieve low power consumption of all DK, not for the nRF91 only.

You can take a look at the DK schematics to see if there is something you can do. You can download the hardware files from the nRF9160 DK product page. But keep in mind we don't recommend using the nRF91 DK as a finished design.

You could instead measure the current on a Thingy:91, which is better suited to be used as a reference design.

Best regards,

Marjeris