Unable to use LDO power on NRF52840

RE: Unable to use LDO power on NRF52840

Simonr — Tue, 18 Nov 2025 08:00:35 GMT

Ah, that makes sense. I didn't realize you had MCUBoot as part of your project as well. Thank you for sharing the solution. Closing this case then. Feel free to reopen if you have any further issues.

Best regards,

Simon

RE: Unable to use LDO power on NRF52840

harryle — Sun, 16 Nov 2025 09:57:39 GMT

Hi Simonr,

It turns out that the MCU boot enable DCDC by default and try disabling it on the app takes no effect. I added this to also the mcuboot.overlay, not just the app overlay, and it worked:
&reg1 { regulator-initial-mode = <NRF5X_REG_MODE_LDO>; };

RE: Unable to use LDO power on NRF52840

harryle — Fri, 14 Nov 2025 07:57:24 GMT

Hi, thank you for your suggestion, I created a blank application and was able to successfully set both reg to disabled. It also worked on our PCB board.

But the firmware of the project I'm working on still failed even with the same setting as the blank one I created. Is there any chance that some component on zephyr can automatically override those config and make the chip use DCDC power instead of LDO?. I'm using UART, BLE, NFC on the project.

RE: Unable to use LDO power on NRF52840

Simonr — Thu, 13 Nov 2025 07:32:41 GMT

The schematics look good. Both DCDCEN registers should be set to 0 (disabled). This should be disabled by default AFAIK, but you can set &reg0 { regulator-initial-mode = <NRF5X_REG_MODE_LDO>; }; to make sure as well. Note that if it has been run with DCDCEN0 enabled at all without the required components, it not certain that you'll be able to reflash the device.

Best regards,

Simon

RE: Unable to use LDO power on NRF52840

harryle — Wed, 12 Nov 2025 04:34:28 GMT

Hi Simonr,

Thank you for your reply. I only removed L2 and L3, not the C16. After removing C16, I can flash firmware to the chip without error. But it seems the firmware is not running. I have attached my schematic here, could you please review it?

About firmware, I'm using NCS v2.9.1, and using default setting now. When run debugging, it found out that under POWER, register DCDCEN has value 1 which is Enabled, and DCDCEN0 has value 0 which is Disabled. Is it the expected value?

RE: Unable to use LDO power on NRF52840

Simonr — Tue, 11 Nov 2025 13:35:01 GMT

The Devicetree setting you set iis indeed the default setting, so making sure this is what is set should be sufficient if you're on NCS v2.8.0 or later. Please confirm which SDK version you're working on.

The behavior you describe doesn't sound typical for when DCDC is enabled but the components are missing, as that usually locks the device up entirely, so I don't think that is it here. Can you say specifically which components you removed from your board? Did you just remove the two inductors or any additional components? There are three extra components added when DCDC is used, so those three should be removed with everything else being untouched:

Best regards,

Simon