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?

  • I guess, if you check GSMA Energy Efficiency for Mobile IoT , page 11, figure 1, you will recognize the difference between "active time" (T3324, or ) and "Inactivity timer". Others use the terms "PSM Activity Timer" and "RRC Activity Timer". So you selected the phase when switching from RRC Connected to Idle, but sleeping is the reached after Idle (in you case 6 minutes). Just wait and measure later.

  • 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.

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

    #include <modem/lte_lc.h>
    void main(void)

    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,

  • 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.

  • > we are able to measure 3uA with that.

    Great, so your setup and device is well.

    > Serial LTE Modem 

    Hm, AFAIK, that uses the UART, does it?

    The standard UART consumes quite a lot, so 60uA seems to be a brilliant value.

  • We turned of the UART using the #XSLEEP cmd, so it cant be the UARTs. I was thinking it might be the SIM card that is still active? Will investigate this further.

Reply Children
  • HI Achim/Dejans,

    I have been able to confirm that the issue is in the Serial LTE Modem application. In the past we have created this ticket, in which  have been able to assist us. There seems to be some a setting that can be disabled/emnabled in the serial lte modem application in order to be able to go into a low power state of 4uA.

    When we upload the 8547.merged.hex file and run it, we are able to go into u 4uA sleep state:

    Possible to advise how to edit the serial lte modem application in order to go into a low power state? We will be using this application in our product as we will be controlling the modem from an external MCU.

    From the ticket:

    Hi, sorry for the late reply. Here a hex file for you: 3005.merged.hex

    It is currently consuming 30 uA in idle, after calling AT#XSLEEP=0, ideally you should see around 2-3 uA. So I will have to look into what changes they made in the newest NCS release v1.6.0 in order to get it down to the expected idle current. Anyways, you should be able to get started with the hex I posted above, and I will get back to you shortly with an updated one.

  • Hi Frikkie,

    In your picture, there is an average current in the selected area of 176.77uA. Could you show the picture where you got 60uA and which area you selected when you got 60uA? 

    For comparison, have you tried simulating the current consumption with Online Power Profiler? What are the results? Could you show the results? Could you show the values used?

    How long is your PSM interval?

    Was SIM card in the board when you performed measurement?

    You can check if you have entered PSM mode and SIM card consumption by following this guide. In addition, ensure that logging over serial port is disabled. Some peripherals might also cause elevated currents. 

    Best regards,

  • Which version of NCS you're using?

    At least in 2.1.0 (please be aware, Nordic seems to be not common to semantic versioning, therefore the 2.1. breaks a lot the 2.0), the documentation Generic AT commands mentions different modes. Maybe you try to update (carefully) to a new version?

  • Hi Dejan,

    Again, in my picture, section 3 is the PSM section, which draws a current of 60uA. As mentioned in the original post, the periodic TAU is 30mins and active time is 6minutes.

    The SIM cards was off course in the board, otherwise we would not be able to attach to the network and get a message of +CEREG: 1,"0001","01A2D002",7,,,"00100110","11100000".

    I do not see how the online power profiler is going to make any difference. We are supposed to measure 4uA in PSM mode and we are not.

    As mentioned the problem is clearly in the serial lte modem application. It would be great if we can get  to provide his insights on this issue, as he has been able to fix this for us before.

  • We are using 1.8.0 at the moment, as that is certified with 1.3.1 on certain networks. Will attempt to use a newer version though to see if it will make a difference.