No LDO current specifications provided

[Rakshita]

have been reviewing the nRF54L15 datasheet but could not find the current consumption specifications for LDO mode. Is it possible to operate the nRF54L15 in LDO mode? If so, could you please provide the corresponding current consumption specifications or point me to the relevant documentation?

[SwRa]

Hi Rakshita,

The nRF54L15 is not designed to work in LDO mode. LDO mode is not supported and the LDO is for startup only. As per our datasheet: "The device can only be operated in DC/DC mode, but the regulator also has an LDO mode that is used to start up the device." Refer: https://docs.nordicsemi.com/r/bundle/ps_nrf54l15/page/regulators.html-concept_vregmain 

Best Regards,

Swathy

[Rakshita]

Hi SwRa,

And what if inductors are not connected on the pcb, in that case it will be operating in LDO mode right?

[SwRa]

Hi Rakshita,

It is necessary to have the inductors connected. We do not recommend forcing the device to work in LDO mode as it is designed to work in DCDC mode. If you look at the reference designs that we provide, all the designs have DCDC inductors in them.

Regards,

Swathy

[Wojciech O.]

Hi,

I have a related question concerning the nRF54L series, particularly the nRF54LM20A.

We are investigating whether it is technically possible to operate the device without the external VREGMAIN inductor. This is for a future application in which inductive components cannot be used.

Looking at the VREGMAIN block diagram, it appears that the startup LDO supplies DECA, while DECD is normally supplied by the DC/DC converter.

Instead of connecting DECD to DECA/DECRF, we are considering supplying DECD from an external, regulated 0.9 V source, while keeping the internal DC/DC converter disabled.

Could Nordic clarify the following points?

1. Is externally supplying DECD with 0.9 V electrically permissible, even if this configuration is not officially supported?

2. What are the nominal and maximum current requirements of DECD, DECA and DECRF, including peak currents during radio transmission?

3. Does VREGMAIN actively drive DECD while operating in startup LDO mode, potentially causing contention with an external supply?

4. If no inductor is detected at DCC, will the device remain operational in LDO mode, provided that DECD is externally powered?

5. Are there any power sequencing, back-powering, voltage tolerance or internal protection constraints that would make this approach unsafe?

We understand that Nordic recommends the reference DC/DC circuitry for normal operation. Our question is specifically about the internal power architecture and the feasibility of an externally regulated supply in an inductor-free design.

Thank you for any technical clarification you can provide.