PSM floor current is 60uA not 4uA

Hi there, 

We are running a power consumption test using PSM mode, and we are however not measuring the 4uA floor current as expected.

We are requesting a active time of 6 minutes, and TAU time of 30minutes. We are also using eDRX.

However after the active time has passed, the device does not go into a low power state. There also appears to be a lot of noise:

I can confirm that the network does assign us the correct timers, as we get the following message in:

+CEREG: 1,"0001","01A2D002",7,,,"00100110","11100000"

Kindly advise what can be the issue here?

Parents Reply
  • Hi Achim,

    I did not select the phase where it goes from RRC connect to Idle. I selected the phase during which idle time (as you can see in the figure, 6 minutes of multiple eDRX cycles occured) goes to sleeping. The "inactivity timer" is present in the very first spike, I am just zoomed out a lot.

    I have waited more than the 30minutes periodic TAU, which comes in successfully after 30minutes as expected. So I guess there is indeed an issue with the PSM.

    The current in the sleeping state sits around 60uA.

Children
  • > I am just zoomed out a lot.

    Indeed, I wasn't able to see that in the chart.

    Which device are you using nRF9160-DK, Thingy:91, Custom device?

    The 4uA are for the nRF9160-DK, 40uA are a Thingy:91, if you switch off the sensors. At least , that's my experience.

  • Apologies for not mentioning we are on the nRF9160-DK. We are able to reproduce this on multiple networks. We are running modem firmware version 1.3.1.

  • Did you try to follow getting started with current measurements on the nrf9160 ? Using

    #include <modem/lte_lc.h>
    void main(void)
    {
     lte_lc_power_off();
     k_sleep(K_MSEC(1000));
     NRF_REGULATORS->SYSTEMOFF = 1;
    }

    you switch of all and that should the result 4uA. if not, may be some different jumpers or connected components are used?

    Or your DK is "broken".

  • Hi Frikkie,

    There are several online resources available related to power estimation and consumption - power optimizationonline power profiler for nRF91 and optimizing power for nRF52 designs. You may get some insights into what could potentially be wrong by reading provided online resources.

    RRC inactivity timer determines the amount of time UE should spend in RRC connected mode before going to RRC idle mode and it is determined by the network. PSM active mode specifies the amount of time UE spends in RRC idle mode before going to PSM mode. It might be that you never reach PSM mode.

    Could you please provide more information about your measurement setup?

    It would be useful if you could use different colors to mark all time intervals that you used in the picture you provided.  Additionally, you could use online power profiler for LTE for initial estimation of the power consumption. Could you provide a screenshot of the results from online power profiler? How much do the results differ from the results obtained using your test setup? How did you measure the current in the sleeping state? Could you show this on the picture from Power Profiler application?

    Best regards,
    Dejan

  • Hi Dejans,

    Thanks for your response. We have done these tests multiple times in the past (prob a year ago) and we are revisiting the usage of PSM mode. I do understand the different states regarding the inactivity time when in RRC connected,  RRC idle as well as PSM. We are definitely entering PSM mode in the graph of my original post.

    Section 1 is the attach process, which includesthe RRC inactivity timer of around 3seconds. Section 2 is the entire RRC Idle time of 6 minutes as requested, Section 3 onward is then supposed to be PSM mode, where we measure 60-70uA instead of the expected 4uA. Section 4 is the edrx cycles of 10.24sec. After 30minutes, which was the requested periodic TAU using +CPSMS, we do see the TAU on the profile indicating that we were indeed in PSM mode.

    Our setup is using the PPK2 in source meter mode at 3.6V, as specified in the doc Achim linked. I also ran the low power test by uploading the .hex file in the link of the doc, and we are able to measure 3uA with that.

    We are running the stock Serial LTE Modem application with modem fw version 1.3.1, and we then send some at commands using the LTE Link Monitor app.

Related