sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE) no effect on power consumption

[Allen]

Hello,

I am working on a wearable device and need the lowest power consumption possible. The project configuration is:

• S132 7.2.0
• SDK 17.0.2

The board is powered with a bench power supply which displayed current to mA resolution. I am not seeing any difference in power consumption when the DC/DC regulator is enabled. In previous projects there was a significant difference when this feature was enabled. It does not matter if it is before or after enabling the soft device/BLE.

[Allen]

Below is the code from main.c  I experience the same amount of current draw with or without the dcdc mode statement. Could any of those other modules prevent that from working>

    // Initialize power management
    sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);

    ret_code = nrf_pwr_mgmt_init();
    APP_ERROR_CHECK(ret_code);
 
    NRF_LOG_INFO("Initialization complete");

    // Initialize Command Line Interface
    ret_code = nrf_cli_init(&m_cli_rtt, NULL, true, false, NRF_LOG_SEVERITY_INFO);
    APP_ERROR_CHECK(ret_code);
    ret_code = nrf_cli_start(&m_cli_rtt);
    APP_ERROR_CHECK(ret_code);

    advertising_start();
    battery_svc_start();

    while (true) {
        //if (data_ready && connected && !isBusy()) {
        //    //send data.
        //    sensor2_characteristic_update(&m_sensor_service, get_flash_result());
        //    data_ready = false;
        //}

        // Execute the scheduler upon waking up from an event or interrupt.
        nrf_pwr_mgmt_run();

        // Polled execution of services
        nrf_cli_process(&m_cli_rtt);
        app_sched_execute();
        //NRF_LOG_FLUSH();
    }

[Jørgen Holmefjord]

No, I can't see anything in the code that should prevent DCDC from being enabled.

Did you initialize the softdevice before this code? I see that you are not checking the return code from sd_power_dcdc_mode_set(), but the power mode looks correct, so it should return success.

Can you read out NRF_POWER->DCDCEN at a later point in the application execution with a debugger, to see that the mode is actually being set?

If you could also try my suggestion above, that would be helpful.

[Allen]

Yes, the soft device is initialized before enabling the DC-DC mode. This is done with the BLE stack is initialized.

Verified with a debugger that NRF_POWER->DCDCEN is 0 before the call and 1 after the call.

Should the power consumption drop immediately after the DC-DC is enabled? Where can I find a description of the operation?

I have a Power Profiler Kit on order. It is currently back ordered. Will try when that arrives.

[Jørgen Holmefjord]

Yes, the current should drop immediately. I created a test-project to show this, which has a 3s delay at the start of main, then enable DCDC, then just busy-loops:

int main(void)
{
    nrf_delay_ms(3000);
    NRF_POWER->DCDCEN = 1;

    while (true);
}

The result can be seen in below capture from the PPK:

As you can see, I marked the area where the current consumption is high is 2.962s (if I had marked the area more precise, I'm sure it would have been very close to exactly 3s).