Current measurement of nrf52840

RE: Current measurement of nrf52840

Jared — Tue, 03 Dec 2019 13:56:21 GMT

Hi,

Usually we recommend connecting the connector J3 NRF_USB if the USB interface is used. However, we don't recommend connecting the J2 connector that powers the interface chip "due to added supply and measurement noise when the debugger chip USB port is active"

[quote user="runner"]For some reason the base-current is much higher than expected. It should be few uAs not tens of uAs like seen in the attachment. It looks that some interference is causing saw-wave which raise the avg base-current very high. Frequency of the saw-wave is 50Hz which indicates that it is coming from power supply for Otii Arc or though some other path. [/quote]

What exactly is the application doing? Is the nRF in any power saving mode? Are you experiencing the same if you try to power it with a coin cell? What current do you measure if you program the DK with the power profiling application.

regards

Jared

RE: Current measurement of nrf52840

runner — Tue, 03 Dec 2019 10:44:44 GMT

Any news on this?

RE: Current measurement of nrf52840

runner — Tue, 26 Nov 2019 07:31:14 GMT

Hi,

More observations. Obviously P21 is not good place to measure nRFonly current, there might be some grounding issues etc. that makes it sensitive for interference.

I made new connections as shown in the attached picture.

- Cut SB40.

- SW6 to nRFOnly state

- SW9 in VDD state

- SW10 off

- Connect Otii's power supply's + wire to P22's upper pin (the pin closer to P23)

- Connect Otii's - wire to P21's negative-pin.

- Connect J2 to host computer's USB

=> Now I started to get expected figures and the saw-wave disappeared.

Your current measurement guide states in chapter 9 as follows: The current measurements will become unreliable when a serial terminal is connected to the virtual COM port." Is this causing false figures in my new setup, to me they are in range at least? Is there any ways to disconnect the serial terminal and still get reliable figures? I tried to cut SB54, SB55, SB56 and SB57...did not help.

RE: Current measurement of nrf52840

runner — Mon, 25 Nov 2019 09:04:33 GMT

Thanks Jared,

I followed your instructions in my measurements.

For some reason the base-current is much higher than expected. It should be few uAs not tens of uAs like seen in the attachment. It looks that some interference is causing saw-wave which raise the avg base-current very high. Frequency of the saw-wave is 50Hz which indicates that it is coming from power supply for Otii Arc or though some other path.

However it is interesting why this is seen only with nRF52840-DK (pca10056) not with nrf52832 (pca10040). The 840 board seems to be sensitive for interference e.g. if I press components on the board with my fingers it cause quite large envelope to the current consumption curve.

Have you notice this and do you have ideas to make the 840-DK less sensitive for interference?

RE: Current measurement of nrf52840

Jared — Thu, 14 Nov 2019 09:30:43 GMT

Hi,

It's enough to set the board in NRF ONLY mode. You can also disable the voltage follower by cutting SB58 if you're not using the board in high voltage mode which depends on what voltage you're supplying the nRF with. You should use P21 to supply the board with external supply.

regards

Jared