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  • Case ID: 299048
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PSM floor current is 60uA not 4uA

Frikkie Badenhorst

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?

  • 0 in reply to Frikkie Badenhorst

    Hi Frikkie,

    There are several online resources available related to power estimation and consumption - power optimization, online 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

  • 0 in reply to dejans

    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.

  • 0 in reply to Frikkie Badenhorst

    > 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.

  • 0 in reply to Achim Kraus

    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.

  • 0 in reply to Frikkie Badenhorst

    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:

    Stian Røed Hafskjold said:

    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.

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