How to reach datasheet-level 2.9 µA System ON IDLE current on nRF54L15 DK with NCS Matter sample?

[Damon Liu]

We are planning to use the nRF54L15 for a Matter over Thread product, so we are currently evaluating the low-power performance of this device.

According to the nRF54L15 product specification / datasheet, the sleep current for:

is listed as approximately 2.9 µA. Since the nRF54L15 has 256 KB RAM, I expected that it should be possible to observe a sleep current close to this value under the proper low-power configuration.

I used the following setup for the test:

• Board: nRF54L15 DK
• Chip: nRF54L15
• SDK: nRF Connect SDK v3.2.1
• Sample: nrf/samples/matter/window_covering
• Build command:  west build -b nrf54l15dk/nrf54l15/cpuapp -p always -- -DCONF_FILE=prj_release.conf
• Measurement tool: Nordic PPK
• Measurement mode: Ammeter mode
• Measurement point: VDD CURRENT MEASURE on the nRF54L15 DK

Test 1: Original sample without modifications

First, I built and flashed the sample using the original prj_release.conf without any modifications.

In this case, the measured baseline current was about 194.18 µA.

Test 2: After disabling shell/banner/early console

I suspected that some UART/logging-related functionality might still be enabled, so I added the following configurations to prj_release.conf:

CONFIG_CHIP_LIB_SHELL=n
CONFIG_NCS_BOOT_BANNER=n
CONFIG_BOOT_BANNER=n
CONFIG_EARLY_CONSOLE=n

After adding the above configurations, I rebuilt and flashed the application again.

The measured baseline current dropped significantly, and the lowest current I observed was about 8.79 µA.

This is much better than the original result, but it is still higher than the 2.9 µA value listed in the datasheet for System ON IDLE with GRTC and 256 KB RAM.

Questions

1. Is it expected that the Matter window_covering sample on the nRF54L15 DK cannot reach the datasheet-level System ON IDLE current of around 2.9 µA without further modifications?
2. What are the remaining contributors that may keep the current at around 8.8 µA in this sample? For example, could this be caused by Thread/Matter timers, enabled peripherals, DK board circuitry, retained RAM configuration, logging backend, UART state, or other subsystems?
3. What additional project configuration changes, device tree changes, or board-level settings are required in order to observe a sleep current close to 2.9 µA on the nRF54L15 DK?
4. Is there a recommended minimal low-power sample or reference configuration for measuring the lowest System ON IDLE current on nRF54L15?

Thanks.

[Kazi Afroza Sultana]

Hello,

My colleague Amanda is on vacation now. I will work on this case until she is back in office.

I measured the current on the DK after running this window_covering sample. Only changed I have made in the application is adding the follwoing configs in the prj.conf file

CONFIG_SERIAL=n         # Do not initialize UART logger module
CONFIG_POWEROFF=y       # System OFF library

And setting this configuration on the Board configurator

I got average current 4.16uA. PPK was on source meter mode and supply voltage is as same board configurator's supply voltage. 

Can you please tell what is the goal to have 2.4uA as sleep current? 

Thanks.

BR

Kazi

[Damon Liu]

Hi Kazi,

Thanks for testing this on your side.

I tried your suggested configuration:

CONFIG_SERIAL=n
CONFIG_POWEROFF=y

However, in my setup, the measured sleep current is still around 8.x µA, and I cannot observe the 4.16 µA average current level shown in your screenshot.

One difference is that I am using the PPK in ammeter mode, measuring through the VDD CURRENT MEASURE point on the nRF54L15 DK, while you used the PPK in source meter mode.

Could this difference in measurement mode explain the difference between my result and your result?

Also, could you please provide the exact wiring method for measuring the nRF54L15 DK current in PPK source meter mode? I am not fully sure how to connect the PPK to the DK correctly when using source meter mode.

If possible, could you also share the firmware image that you used for your test? Then I can flash the same firmware directly on my nRF54L15 DK and compare the measurement result under the same firmware configuration.

In addition, based on your configuration, I also tried disabling the sample watchdog:

CONFIG_NCS_SAMPLE_MATTER_WATCHDOG=n

After disabling the watchdog, I still observed the same abnormal behavior that I mentioned earlier: the sleep baseline current decreases, but very large current spikes appear in the PPK measurement. The peak current can exceed 500 mA.

Could you please try to reproduce this behavior on your side and help investigate the reason? I would like to understand clearly why disabling the sample watchdog causes such abnormal current spikes.

Regarding your question about the goal of having 2.4 µA as the sleep current:

My target is not exactly 2.4 µA. My reference target is closer to 2.9 µA, because this is the value mentioned in the nRF54L15 product specification for System ON IDLE with GRTC and 256 KB RAM.

Our goal is to make the sleep current of a Matter over Thread product as close as possible to this low-power level.

For comparison, in our previous product based on nRF52840, we were already able to optimize the Matter over Thread sleep current to the 3.x µA range. Based on Nordic’s product positioning and low-power claims for the nRF54L15, we expected the nRF54L15 Matter over Thread solution to be able to achieve similar or better sleep current than nRF52840.

So the main purpose of this case is to understand the correct configuration and measurement method for achieving and verifying the expected low sleep current on nRF54L15 DK with Matter over Thread firmware.

Thanks.