Can´t measure current on the SoCs of my 840 or 833 DK boards

[p143]

Hi All.

I am trying to measure the consumption of the SoCs inside the nRF52840DK and the nRF52833DK using a PPK(II), both running the same code to make comparisons.

First, I insulated the consumption of the DK SoCs following the documentation settings:

• SW10: ON
• SW9: VDD
• SW6: nRF ONLY
• Vcc: 1,8v
• SB40: Unsolded

Second, I set the PPK per the documentation in the Sourcing Meter mode, with a measuring window of 1 min and Vcc at 1.8V.

Results: OK on both boards.

But when I tried to repeat the process in Ampere Meter mode, all the current measurements were zero, and the same happened with an amperimeter

Could you give me a suggestion?

Thanks

[Simonr]

Hi

Please note that the connection from the PPK2 is somewhat different in Source Meter mode compared to Ampere Meter mode, so make sure that instead of the Vout and GND pins connected to the topmost P22 pin and a GND reference, in Ampere Meter mode Vout and Vin should be connected to P22. Also note that in Ampere Meter mode you need an external power source as the PPK2 won't work as a source in this case.

Best regards,

Simon

[p143]

Hi, Simon.

Maybe I didn't explain myself properly. As I mentioned, my setup is as described in Nordic's documentation, which also fits the setup you mentioned. I am referring to the documentation: Power Profiler Kit II, v1.0.1, User Guide, paragraph 6.3, Figure 6, with the footer 4461_012.
However, both in this Nordic documentation and your described setup, it is not mentioned "where" precisely the referred external power supply must be connected, but only the need for it. Could you clarify the matter?

Best Regards
Juan

[Simonr]

Hi Juan

I see. Optimally, the external power source should be a "clean one" I.E. not USB and supplied to P21 for example. For all options to power the nRF52833/840 DK externally, see section 4.3.4 and onwards of the nRF52833 DK HW user guide.

Best regards,

Simon

[p143]

Hi Simon.

The problem was solved, thanks, but I have one more doubt. Now, I'm able to measure current in both modes. Still, I want to make sure that my consumption measurements on the SoC nrf52833 alone, loaded with a specific app, fed from p21, and without any peripheral loading the chip, really reflect the minimum possible current to maximize the battery life or as your documentation is suggesting, in addition, I shall un-cut SB58? This documentation says that the voltage follower gets disconnected by doing this, but it does not clarify if this is relevant to minimizing the SoC consumption measurement.
Thanks again.

Juan

[Simonr]

Hi Juan

You should cut SB58 in order to disconnect the voltage follower from external supply. This will also contribute to minimizing current consumption, but not by a lot. Note that you should make sure the DK is in the nRF Only mode when it is cut.

Best regards,

Simon