Current consumption Nrf9160 and a noise problem when measuring current(?)

[Gal_S]

Hello,

We are trying to figure out how to sum up the size of the system currents.

We use several protocols at the same time, SPI1, I2C, and SPI2.

I understand that it doesn’t make sense to carry out a linear sum of the protocols.

I have two questions,

1) I am trying to understand how to do this.

2) The second question relates to the use of PPK2.

When I measure the current, it seems that there are noises from the USB connection, can it be the reason?  How to reduce this noise?

Attached is a picture of the measurement from PPK2.

[Kenneth]

Hello,

My suggestion is to first start with a simple example (for instance without logging), and then measure on it for comparison before adding more of the functionality to observe the difference. In terms of how to measure etc, please check out:
https://devzone.nordicsemi.com/guides/cellular-iot-guides/b/hardware-design/posts/getting-started-with-current-measurements-on-the-nrf9160 

If you are measuring on an nRF91 DK you should also check out:
https://infocenter.nordicsemi.com/topic/ug_nrf91_dk/UG/nrf91_DK/hw_measure_current.html 

Also check out the description for the PPK2 on how to measure current:
https://infocenter.nordicsemi.com/topic/ug_ppk2/UG/ppk/setting_up.html 

For instance it does say: "Note: Although using USB to power the DUT is sufficient, Nordic recommends a lab power supply to ensure better accuracy."

Best regards,
Kenneth

[Gal_S]

Hi,

Thanks for the answer.
How to calculate the current consumption by combining different protocols?

Regarding the power supply, we are using a PCB and not an EVB, the PCB gets voltage from the power supply.

[Kenneth]

Gal_S said:

How to calculate the current consumption by combining different protocols?

You would need to measure the charge for 1 transaction, and then if you know the time between transactions you could calculate the average as simply charge/time = current (e.g. if the enrgy is measured as 1uC, and you need to read every 100ms: 1uC / 0.1 sec = 10uA).

Kenneth