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

[gwan0624]

I am currently developing a project using an nRF5340DK and a custom board.

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PC ---(SWD)--- IntMCU at nRF5340DK ---(SWD)--- nRF5340 on custom PCB

Custom PCB
- External 32kHz crystal: X
- External Flash memory: X
- Voltage Mode: High Voltage mode
- Internal Regulator mode: LDO
- MCU voltage: 3.3V
- MCU VDD voltage: 1.8V
- SWD signal line voltage: 1.8V (IDK why. But I input 1.8V for VIOREF pin on nRF5340DK to programm my PCB)

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However, the SWD output on the custom board is measuring at 1.8V. (This wasn't my intentional design, but it seems to be the default setting, and I proceeded without modifying it.)

To match this, I used an external power supply to provide 1.8V to the VIOREF and VTG pins of the nRF5340DK, effectively bringing the DK's SWD line voltage down to 1.8V. Debugging was proceeding smoothly with this setup.

The problem occurred during the following instances:

Occasionally, the external power supply was turned off, leaving VIOREF empty. This caused the nRF5340DK’s default 3V output to flow directly into the custom board’s RESET pin.

In other cases, SWD signals were applied to the custom board's pins while the 3.3V main power was not supplied to the board.

Current Symptoms:

- The device is no longer detected by the nRF Connect SDK (shows as "Unknown Device").

- The RESET and VDD outputs on the custom board are unstable (fluctuating).

I suspect that the incorrect voltage levels flowing through the pins have caused hardware damage.

Is there any way to recover from this, or is the chip permanently damaged?

[Simonr]

Hi

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

[gwan0624]

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