Regarding the startup current of the nRF54L bootloader

[talby]

Hi,
I am developing a program for the nRF54L15 with the DFU bootloader enabled.
I would like to reduce the startup current.

I am using SDK 3.2.4.

The `sysbuild.conf` settings are as follows.

SB_CONFIG_BOOTLOADER_MCUBOOT=y

SB_CONFIG_BOOT_SIGNATURE_KEY_FILE="\${APP_DIR}/private_key.pem"

SB_CONFIG_BOOT_SIGNATURE_TYPE_ED25519=y

SB_CONFIG_MCUBOOT_SIGNATURE_USING_KMU=y

SB_CONFIG_MCUBOOT_GENERATE_DEFAULT_KMU_KEYFILE=y

The `mcuboot.conf` settings are as follows.

CONFIG_SERIAL=n

CONFIG_BOOT_VALIDATE_SLOT0=n

CONFIG_SPEED_OPTIMIZATIONS=y

CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y

When booting with these settings, an average current of 1.8 mA flows for a period of approximately 470 ms, as shown in the image below.

What operation is causing this current draw?

Is it possible to further reduce the current or shorten this duration?

Best regards.

[Simonr]

Hi

After reviewing this issue and discussing it with a colleague, this seems to be a bug with the order of which things are started in the later NCS releases so that other peripherals are active at the time the 32kHz LF clock is being called and starts up.

We have now started investigating what exactly these are and how this can be fixed for NCS 3.4.0. I will keep you updated when I here more from the developers on this.

Thank you for your patience,

-Simon