nrf52840 pca10056 eval board running sdk example ble_app_pwr_profiling_pca10056_s140 system off current profile implies something is still running at about 2kHz

[willml]

I have the debug section of the evaluation board turned off, modifications to measure current with a DMM set up, and am using a keysight 34465a DMM to measure current.  The DMM reports this for the current profile when the processor goes to system off

:

I have the DC-to-DC converter turned on (NRF_POWER->DCDCEN = 1, have called sd_power_dcdc_mode_set(1) after the power_management_init() call.   What else do I need to turn off to get the 2kHz spikes to go away?

Thank you,

--bill

[bjorn-spockeli]

This is the regulator operating in refresh mode. From the product specification:

• Auto-controlled refresh modes for LDO and DC/DC regulators to maximize efficiency

Both the LDO and DCDC have two modes of operation. Normal mode and refresh mode. Refresh mode is used when the current consumption is low in order to further maximize the efficiency. Refresh mode works by charging up internal caps regularly to provide power to the chip. So the spikes you see is the inrush current to the caps.

See https://devzone.nordicsemi.com/f/nordic-q-a/14210/current-spikes-when-dcdc-is-on/54282#54282.