Confused about switching between DCDC and LDO with macros found in sdk_config.h

[abtj]

We are using the nRF52840 with SDK 15.3 and we want to switch the regulators (DCDC or LDO) manually depending on the feature.

According to the Nordic document here (https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf52840%2Fpower.html&cp=4_0_0_4_2), it looks like LDO regulators are used by default. After reading other threads, I found out that sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE) will enable DCDC regulators and sd_power_dcdc_mode_set(NRF_POWER_DCDC_DISABLE) will enable LDO regulators. I see that there are NRFX_POWER_CONFIG_DEFAULT_DCDCEN and NRF_POWER_CONFIG_DEFAULT_DCDCENHV in sdk_config.h and I was wondering if they must be set to 1 in order for us to be able to use DCDC regulators. Also, does that mean NRFX_POWER_ENABLED needs to be set to 1 as well?

[Simonr]

Hi

Are you using a SoftDevice in your application? If not, enabling the DCDC can be done by directly writing to the registers:

NRF_POWER->DCDCEN = 1;

If you're using a SoftDevice, you can still use this approach, but you'll need to set it before enabling the SoftDevice. After enabing the SoftDevice you will need to use the sd_power_dcdc0_mode_set() or sd_power_dcdc_mode_set() functions as you say.

The sdk_config.h calls are an alternative as well, but then you need to initialize the POWER driver for the config to take effect. Please note that if you're using a SoftDevice you should use the legacy power driver, as the nrfx version does not integrate with the SoftDevice.

Best regards,

Simon