Power Profiler Kit 2 Reading Low and High

[edmcnicholas]

Hello I have a board that I am trying to profile with the power profiler kit 2 and the readings seem very wild.  I have a device that I know the base configuration with the sensors on is about 100uA measured with a fluke multimeter.  The issue I am seeing is that I am getting current levels between 2uA and 30mA with the BLE on and I can not get a steady state current.  This is the case with 2 separate PPK2 win Ampere Meter mode and Source Mode.  In source mode the current spikes show over 100mA.  it seems that the auto sensing is a bit haywire.  I am using the latest release of the power profiler sw.

From my measurements I should not be going below 20uA even with the sensors off and I am seeing sub 1uA for several mS even with a rate of 100k samples per second.

[Einar Thorsrud]

Hi,

It looks like you are seeing the LDO refresh mode. When the device is consuming low power, the regulator will be turned off most of the time, and only be enabled for a short while to optimizse average current consumption. You will see that as a sequence of spikes when you observe this witha  PPK or power analyzer or similar. When you measure the idle current with a multimeter you will not see this spikes, but instead see the average current.

[edmcnicholas]

But I am doing this in ampere meter mode. Would that still be the case.  I know I have an rms in one state of 150ua and it is flat since it is a sensor front end.

[Einar Thorsrud]

Yes, it would stil be the case, as the nRF itself use refresh mode when the current consumption is low. In this case the current consumption will be close to zero most of the time, except for when the regulator is on for a short time to charge up internal capacitors.

[edmcnicholas]

so how would I get good measurements if this is the case?

[Einar Thorsrud]

Is the question how you can measure the avarage current during an interval? If so, you can select the range you want to measure and look at the average number (you get one both for selection and the whole window). 

[edmcnicholas]

What i am asking is that if i know the measurement should be about 100uA steady state without much fluctuation as it is an amplifier circuits quiescent current how do i get a proper reading when I see that most of the time it is almost 0 and the spikes are not at my average current.  if it is in 100k sample per second mode i would expect it to be properly sampling at that rate without just drastic fluctuations especially in ampere meter mode.