nRF52832 (nRF Connect SDK 1.9.1) : Unidentified current spikes (700 *µA ~1ms)

[Allan P]

Hello,

I'm evaluating power optimization on nRF52. I'm using a Power Profiler Kit II and a nRF52-DK board.

I tried a lot of configuration and everything work as expected.

My problem here is that I can't get rid of 700µA spikes each 1ms, some of them are skipped. See below :

I'm using the test beacon default project, I removed the BLE, so I'm measuring only the idle.

My .conf file :

CONFIG_BT=y

CONFIG_BT_DEBUG_LOG=n

CONFIG_BT_DEVICE_NAME="Test beacon"

# Drivers and peripherals

CONFIG_ADC=n

CONFIG_I2C=n

CONFIG_WATCHDOG=n

CONFIG_PINMUX=n

CONFIG_SPI=n

CONFIG_IS_SPM=n

CONFIG_FW_INFO=y

CONFIG_GPIO=y

CONFIG_SERIAL=n

# Power management

#CONFIG_SYS_POWER_MANAGEMENT=n

CONFIG_PM=y

CONFIG_PM_DEVICE=y

CONFIG_TICKLESS_KERNEL=y

#CONFIG_TICKLESS_IDLE=y

# Interrupts

CONFIG_DYNAMIC_INTERRUPTS=n

CONFIG_IRQ_OFFLOAD=n

# Memory protection

CONFIG_THREAD_STACK_INFO=n

CONFIG_THREAD_CUSTOM_DATA=n

CONFIG_FPU=n

# Console

CONFIG_CONSOLE=n

CONFIG_UART_CONSOLE=n

CONFIG_STDOUT_CONSOLE=n

CONFIG_PRINTK=n

CONFIG_EARLY_CONSOLE=n

Is there a way to get rid of those spikes ? What is causing them ?

Thanks.

[Stian Røed Hafskjold]

Hi, these spikes are caused by noise from the USB port.

You have two options, either unplug the USB cable and power the DK with a clean supply on the power supply header. Then you can measure current going through the current measurement header with the PPK2 in ampere meter mode.

Alternatively you can leave the USB plugged in, but then you will have to power the nRF52 from the PPK using source meter mode. Connect the GND from PPK to GND on the DK, and VOUT from the PPK to the nRF52 side of the current measurement header (the pin closest to the debug out header). Then you need to adjust the PPK2 output voltage to match the VDD voltage on the DK exactly. I believe it should be around 2.7V.