PPK2 showing Different current reading on different sampling rate settings

RE: PPK2 showing Different current reading on different sampling rate settings

Searcher — Fri, 24 May 2024 08:05:14 GMT

Thanks very much for the explaination. Stian Røed Hafskjold

RE: PPK2 showing Different current reading on different sampling rate settings

Stian Røed Hafskjold — Wed, 22 May 2024 14:01:15 GMT

Hi, this is normal and is called refresh mode. When the current consumption is low, the regulator turns off to save power, and internal current is only drawn from the DEC4 capacitor (regulator output). The spikes you see is the regulator waking up to recharge the DEC4 capacitor. If you probe the DEC4 voltage you will see that there is a corresponding saw tooth shape to the input current.

RE: PPK2 showing Different current reading on different sampling rate settings

Searcher — Wed, 22 May 2024 02:03:04 GMT

When will the current range switches? I met an issue that average is 0.48uA, but the max is 18.48uA(every 200ms the current spikes will appear).

RE: PPK2 showing Different current reading on different sampling rate settings

Stian Røed Hafskjold — Tue, 31 Oct 2023 11:08:48 GMT

Hi,

The lab equipment used was a Keysight N6705B. Measurements were conducted individually, on the same DUT. Both PPK and N6705B were configured in source meter mode with 3V output.

RE: PPK2 showing Different current reading on different sampling rate settings

ATla5 — Mon, 31 Jul 2023 07:31:34 GMT

Hello,

I want to investigate the artifacts of the current measurement caused by the PPK2 and I want to know

1. The type of (professional lab) measurement equipment including settings used to perform the measurement.

2. Was the current measurement performed with the PPK2, nRF52840 and the professional lab equipment in series or individually meaning first PPK2 and nRF52840, then the professional equipment and the nRF52840.

In general I would appreciate more details about the measurement setup.

Best regards

ATla5

RE: PPK2 showing Different current reading on different sampling rate settings

Stian Røed Hafskjold — Wed, 04 Jan 2023 10:26:22 GMT

[quote user="dnyaneshvar"]So for waveforms other than mentioned above how can I identify the current spikes shown by PPK2 KIT are due to the artifact from the PPK2 itself and is not part of the actual current?[/quote]

You can identify the artifact by looking at the current before and after. When it switches measurement ranges, i.e. going from a low current consumption to a high current consumption, it may overshoot.

RE: PPK2 showing Different current reading on different sampling rate settings

dnyaneshvar — Wed, 04 Jan 2023 07:44:40 GMT

Hello Stian Røed Hafskjold,

When that is said, the PPK2 sometimes shows current spikes when the current range switches. This is an artifact from the PPK2 itself and is not part of the actual current.

By comparing the two Images above, I can see that there are current spikes in waveform measured by PPK2 kit and for same section measured by the professional tool mentioned by you, there isn't any current spikes.

I don't have the sophisticated professional tool the one you are using (as of now at least).

Currently I am limited to use PPK2 KIT only.

So for waveforms other than mentioned above how can I identify the current spikes shown by PPK2 KIT are due to the artifact from the PPK2 itself and is not part of the actual current?

RE: PPK2 showing Different current reading on different sampling rate settings

Stian Røed Hafskjold — Tue, 03 Jan 2023 17:25:48 GMT

Hi Dnyaneshvar,

I took over this case from Håkon who is out of office.

[quote user="dnyaneshvar"]How the current of 1.4mA becomes 15.5mA when sampling frequency changes from 100 to 100 000 samples per seconds?[/quote]

When the sampling frequency decreases, the reported instantaneous current is based on the average over a longer period. If you have very short spikes which are shorter than the sampling period, you will not be able to measure the maximum.

The length of the TX and RX peaks are in the 100 us range, hence you will need a sampling frequency of 20000 samples per second or higher in order to capture the TX or RX peak current. If you zoom in on the advertising interval at 100000 samples per seconds, it will probably be more clear, and easier to see what the advertising event actually consists of.

When that is said, the PPK2 sometimes shows current spikes when the current range switches. This is an artifact from the PPK2 itself and is not part of the actual current. Here is an advertising event measured with a professional lab equipment compared with the PPK2:

The radio TX peak current is the flat area at 6.3mA.

The peaks will vary based on the load impedance, so it may look different when measuring on your board. Please note that the average current or the total charge over the advertising event will be correct. You can also compare the measurements with the online power profiler: Online Power Profiler for Bluetooth LE

RE: PPK2 showing Different current reading on different sampling rate settings

dnyaneshvar — Fri, 23 Dec 2022 07:28:50 GMT

Hi helsing,

1) The average current consumption is the most important measurement to pay attention to. - Okay.

2) If you sample at a lower sample rate, then the largest spikes will have been averaged out over the sample interval.

This will result in the maximum current displayed as lower than for high sample rate.- I am talking about the instantaneous values of current. Instantaneous current consumed by advertising interval of load device. It can be clearly seen that it's values measured by PPk2 are all different at four different sampling rate.

Yes, Averaging is done with respect to the sampling frequency, I agree.

Increasing sampling rate would result in increase in the accuracy of measured parameters.

But how come the value of instantaneous current consumed become different for different sampling rate.

How the current of 1.4mA becomes 15.5mA when sampling frequency changes from 100 to 100 000 samples per seconds?

RE: PPK2 showing Different current reading on different sampling rate settings

helsing — Tue, 13 Dec 2022 14:55:26 GMT

Hi Dnyaneshvar, sorry for the delay.

The average current consumption is the most important measurement to pay attention to. If you sample with at a high sample rate and read out maximum current, you get to see where the largest current spikes are. If you sample at a lower sample rate, then the largest spikes will have been averaged out over the sample interval. This will result in the maximum current displayed as lower than for high sample rate. The average current is still very similar.

The schematics for PPK2 can be found on our website if you would like to take a closer look.

Hope this answers your question.

RE: PPK2 showing Different current reading on different sampling rate settings

helsing — Mon, 12 Dec 2022 10:01:37 GMT

Hi Dnyaneshvar,

I will look into this and get back to you.