Issue with failing VDD output – Is recovery possible? (nRF5340)

RE: Issue with failing VDD output – Is recovery possible? (nRF5340)

gwan0624 — Tue, 17 Mar 2026 08:04:36 GMT

Thank you for your response.

Unfortunately, since the VDD pin was not broken out on the custom board (only VDDH was), I believe I'll need to manufacture a new PCB.

Also, as you suggested, I will strengthen the protection for the SWD lines.

Best regards.

gwan0624

RE: Issue with failing VDD output – Is recovery possible? (nRF5340)

Simonr — Thu, 12 Mar 2026 07:34:25 GMT

Hi again

The VTG is a sense pin that's there for the debugger MCU to detect whether there is an external board connected or not so it knows which device to program.

The resistors and switch on the SWD line is indeed protection components.

Note that we can't recommend that you power the VTG pin separately, and this should also come from the custom board so that the sense mechanism is only in play when the custom board (and VTG) has power. Here's the correct setup for a custom board to be programmed from the nRF5340 DK.

Best regards,

Simon

RE: Issue with failing VDD output – Is recovery possible? (nRF5340)

gwan0624 — Tue, 10 Mar 2026 15:50:55 GMT

Thank you for your response.

I have already attempted the "recover" process multiple times across various environments, including nRF Connect for Desktop, Ozone, and VS Code. However, since the device itself is not being recognized at all, all attempts have failed. It seems highly likely that the VDD pin is indeed damaged.

In light of this, I was wondering if the nRF5340DK includes specific circuitry to prevent such issues. I’ve noticed a few features on the DK, such as:

A mechanism that only connects to the external target upon receiving VTG.
150 Ohm resistors on the SWD signal lines.
The switch located between the Interface MCU and the nRF5340's SWD line.

Could you confirm if these components actually serve to protect the nRF5340? As I am planning to design a new module, I would rather rely on robust voltage protection circuits than just following a specific "power-up sequence." by my hands

Best regards,
gwan0624

RE: Issue with failing VDD output – Is recovery possible? (nRF5340)

Simonr — Tue, 10 Mar 2026 14:31:49 GMT

Unfortunately it sounds like the board might be damaged here. You should always be careful to have the board supplied when also supplying pins on it externally. Also, for programming external boards with the nRF5340 DK, it is recommended to power the external board separately from the DK (like you do). The voltage on the external board must match that of the DK, which is 3V when the DK is powered from the USB connector. https://docs.nordicsemi.com/bundle/ug_nrf5340_dk/page/UG/dk/ext_programming_support_P20.html

You can try running nrfutil device recover to recover the board, but I wouldn't hold my hopes too high here. The current outputs doesn't look great.

Best regards,

Simon