How switch between LDO and DCDC in prj.conf or during runtime with C?

[MarcelR]

Hi,

I use nrfconnect SDK 3.1.1 and nRF52840 (as a dongle, DK etc)

Using the power profiler kit 2 I see legacy advertising (TX/RX) peaks of about 32mA (with txpwr=8dBm, 3.2V, 100ms).

Checking your online power profiler this tells me I must be using LDO (eating 40.38µC for a payload of 23bytes).

How can I switch to DCDC regulator in my prj.conf, or even better, in my C code?

According to your online calculator this would reduce peaks to 15.5mA (eating only 21.36µC).

[Håkon Alseth]

Hi,

 

To enable DCDC, you can add this to your board:

&reg1 {
	regulator-initial-mode = <NRF5X_REG_MODE_DCDC>;
};

 

Please note that you have to ensure that your design has DCDC inductors in-place before flashing this firmware.

or even better, in my C code?

You can include "nrf.h" and write directly to the registers:

https://docs.nordicsemi.com/bundle/ps_nrf52840/page/power.html#register.DCDCEN

https://docs.nordicsemi.com/bundle/ps_nrf52840/page/power.html#ariaid-title43

ie. NRF_POWER->DCDCEN = value;

  

Please note, reg0 is usually not used, as per this part of the docs:

https://docs.nordicsemi.com/bundle/ps_nrf52840/page/power.html#ariaid-title3

  

Kind regards,

Håkon

[MarcelR]

Thank you for the details.

In my C code, I switch now between LDO and DC/DC with these calls:

#include <hal/nrf_power.h>
// query:

bool wasDcdc = nrf_power_dcdcen_get(NRF_POWER);
...
// set:

nrf_power_dcdcen_set(NRF_POWER, true); // false for LDO

nrf_power_dcdcen_vddh_set(NRF_POWER, true);

It seems to work fine on my nRF52840-DK, - reduced current to about half.

I will, as next step, try the same on my nRF52840-Dongle (hoping it has some LC food around to support REG1 DCDC).
The dongle has no USB power (no REG0) and is running with external regulated source (SB2 cut, SB1 soldered)
...

[Håkon Alseth]

Hi,

 

The nRF52840-dongle has inductors in the design, I suspect you will have similar results as you do on the DK that you tried.

 

Let me know if you run into any issues.

 

Kind regards,

Håkon

[MarcelR]

Yes, works perfectly with nRF52840-Dongle as well

Thank you
Marcel

[MarcelR]

Ohh, my code does not compile anymore for nRF54L15 as

nrf_power_dcdcen_set()

is not known.

CONFIG_BOARD_ENABLE_DCDC=y
or

CONFIG_SOC_DCDC_ENABLE=y

does not compile either.

How is LDO versus DCDC handled in prj.conf, or better in C dynamically, for nRF54L15?

[Håkon Alseth]

Hi,

 

nRF54L-series devices require DCDC to always be on. The reference design options are not valid without DCDC in-place:

https://docs.nordicsemi.com/bundle/ps_nrf54L15/page/chapters/ref_circuitry.html

 

Kind regards,

Håkon

[MarcelR]

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