Power Profiler showing negative current for external DUT

RE: Power Profiler showing negative current for external DUT

Jared — Thu, 05 Nov 2020 14:23:07 GMT

Hi,

The answer from my colleague was related to an older version of the PPK. The issue should not be present in current versions.

regards

Jared

RE: Power Profiler showing negative current for external DUT

_armin — Wed, 04 Nov 2020 18:32:51 GMT

Hi, it is System ON IDLE.

Can you please confirm that the link I posted is irrelevant for my issue, and that the PPK can actually be supplied from USB:

If the PPK USB supply is faulty, then there is no point in trying this setup for measurement?

RE: Power Profiler showing negative current for external DUT

Jared — Tue, 03 Nov 2020 10:10:59 GMT

Hi,

The thing is that if you're going to use the PPK on top of the DK then the PPK voltage should match the DK voltage. If it doesn't, you risk current leakage and erroneous current readings. I suggested configuring the connection as in the figure in my previous reply since the voltage of the external DUT didn't match the DK voltage. It seems that you don't longer have negative current readings but still measure a higher current then you expected. Now, what application are you running on the DUT when you measure? And what do you mean by low power? System OFF or System ON IDLE?

RE: Power Profiler showing negative current for external DUT

_armin — Thu, 29 Oct 2020 20:28:03 GMT

Hi, I have tried the one where PPK uses USB for power supply, and I am getting different, but still bad results. Now the current is always shown to be in the range of 5 to 10 mA while in low-power mode, instead of going below zero like before (when I lower the voltage).

The link I posted earlier seems to suggest that USB supply is faulty on the PPK, so not sure if trying an external power supply would help? I could try that if there is reason to believe it can work, but it is a little inconvenient so would like to avoid doing it if it cannot be helpful.

Here is the link regarding the PPK USB power supply again:
devzone.nordicsemi.com/.../power-profiler-graph-is-in-negative-region-and-average-current-also-appears-to-be-negative

Any other ideas on what else to try?

RE: Power Profiler showing negative current for external DUT

Jared — Wed, 28 Oct 2020 15:04:51 GMT

Hi,

I understand, this is as expected. Measuring with just the PPK ontop of the DK with the power select being set to REG will result in invalid results.

Could you try to connect it as shown in this figure, with the J-link being the debugger onboard the DK. Use a 10 pin-connector to connect the DK to the PPK.

regards

Jared

RE: Power Profiler showing negative current for external DUT

_armin — Tue, 27 Oct 2020 19:21:08 GMT

I meant that I am measuring these values by the PPK itself and the Power Profiling app, without an external device connected at all.

I tried the power profiling application, I am getting the same results.

Could this be an issue with PPK or the Power Profiling app, or the setup I am using? Getting constant reverse current of 1 - 2 mA with just PPK connected to the external DUT seems to suggest this (no other power sources are connected).

RE: Power Profiler showing negative current for external DUT

Jared — Mon, 26 Oct 2020 14:31:06 GMT

[quote user="_armin"]One more thing, not sure if this is expected or can in any way help - if I disconnect the external DUT from the PPK, when I increase the voltage, I get a current of around 65 uA, and when I lower the voltage below 2 V, I get around -230 uA. If I reset the PPK and lower the voltage then, it shows it go down to -0.8 nA, and if I increase the voltage it goes up to 300 uA.[/quote]

How do you measure the current after you've disconnect the PPK? What do you measure if you flash the board with the power profiling application?(Remember to replace the board file)

RE: Power Profiler showing negative current for external DUT

_armin — Wed, 21 Oct 2020 17:08:24 GMT

The current I measure changes quickly with output voltage, it goes below zero when the voltage is around 2.05 V, and it goes down to -1.5 mA when I lower the voltage to 1.95 V. As the voltage is raised above 2.05 V, it reaches a few mA (positive).

External DUT is not connected to anything, only to the PPK, and I have verified that I get the output voltage which I set in Power Profiler app.

The board that I am testing is Acconeer's XB122 breakout board with XM122 module connected to it. I am not sure if I can upload the schematic here (legally speaking), but you can probably gain access to it easily on the Acconeer's website.

One more thing, not sure if this is expected or can in any way help - if I disconnect the external DUT from the PPK, when I increase the voltage, I get a current of around 65 uA, and when I lower the voltage below 2 V, I get around -230 uA. If I reset the PPK and lower the voltage then, it shows it go down to -0.8 nA, and if I increase the voltage it goes up to 300 uA.

Thanks,

Armin

RE: Power Profiler showing negative current for external DUT

Jared — Wed, 21 Oct 2020 14:00:09 GMT

Hi,

How much negative current are you measuring? Is the external DUT connected to anything? Can you measure on the PPK output and verify that it's actually 2V? Also, could you upload the schematic of the DUT?

[quote userid="91521" url="~/f/nordic-q-a/67432/power-profiler-showing-negative-current-for-external-dut"]

I have found a similar issue on the DevZone, and the answer here is that PPK cannot be stacked on top of the DK when using the voltage regulator (if I understood it correctly):

[/quote]

The DK and the PPK can be stacked when you use the regulator but you should not use the regulator if you're measuring current on the DK.

regards

Jared