PPK2 test peak current inaccuracy

RE: PPK2 test peak current inaccuracy

sunmnengnan — Wed, 26 Jun 2024 09:11:39 GMT

I got it. Thanks！

RE: PPK2 test peak current inaccuracy

PaKa — Tue, 18 Jun 2024 10:41:51 GMT

Depends on a lot of parameters. If you are running 3.0V it should be about 7mA with the CPU in Idle and about 9mA with the CPU active. This is with the DCDC enabled. If you are not using the DCDC then the current will be almost double. If you reduce the operating voltage then the current with DCDC will go up while the current with LDO will stay more or less the same.

infocenter.nordicsemi.com/.../pmu.html

I recommend checking out the online power profiler Online Power Profiler for Bluetooth LE as that can give you some ideas on what to expect for average current. The peaks are averaged out here as well so may be lower than what you can see with an oscilloscope

RE: PPK2 test peak current inaccuracy

sunmnengnan — Tue, 18 Jun 2024 09:40:54 GMT

Thank you for your answer.

So should the peak transmit current of the chip at 0dBm be 15mA or 6mA?

RE: PPK2 test peak current inaccuracy

PaKa — Tue, 18 Jun 2024 08:52:48 GMT

The sampling rate inside the PPK is always the same. When you change the timebase in the user interface the data is averaged before sending over. This is what "removes" the spikes as they will be averaged out. When using the spike filter, the average will still be the same, it just removes the spikes from the display to make it easier to view.

TLDR; the peak current with the 10K will be OK as long as the pulses are long enough, if they are really short then the peak may be too low due to averaging. The average will always be OK independent of the sampling range. If you need better peak current detect then you may try to use an oscilloscope.

RE: PPK2 test peak current inaccuracy

sunmnengnan — Tue, 18 Jun 2024 08:06:07 GMT

Is the peak current picked up at 10K sampling rate closer to the actual value?

RE: PPK2 test peak current inaccuracy

sunmnengnan — Tue, 18 Jun 2024 07:54:56 GMT

I see，thank you！

RE: PPK2 test peak current inaccuracy

Simonr — Tue, 18 Jun 2024 06:23:18 GMT

They won't be incorrect, but with less samples it will of course catch less of the super short peaks and valleys of a measurement. The average will still be approximately the same, but you will catch fewer of these voltage shifted spikes that you also see the power analyzer mitigates in HW with stronger components.

Best regards,

Simon

RE: PPK2 test peak current inaccuracy

sunmnengnan — Mon, 17 Jun 2024 01:23:06 GMT

Does it mean that the sampling rate is adjusted to 10,000 times per second and the peaks captured are incorrect? Should I just go with what the power analyser picks up?

Thank you for your reply.

RE: PPK2 test peak current inaccuracy

Simonr — Thu, 13 Jun 2024 13:29:16 GMT

This very much looks like the phantom spikes you can see in current consumptions where the current draw changes rapidly. This is because of the level shifters in the PPK2 aren't able to reduce the voltage spikes as well as expensive oscillators are, so very brief high spikes can be seen. They are only caught at the 100,000 samples per second sampling because they are so brief, so lower sampling rates aren't able to catch them. They should be so brief that they don't affect the total average current, but they are indeed present. You can open the advances settings on the Power Profiler app with ctrl+shift+alt+A to try and tweak the voltage spikes parameter to mitigate this. The simpler fix will be to just use the lower sampling rate.

Best regards,

Simon