Programming external MCU with nRF5340 DK

[mm784]

Hello

I want to clarify something because there seems to be a lot of conflicting information on Dev Zone, and the nRF5340 DK documentation doesn't specify the following:

Can the DK be used to program external boards with VDD other than 3.0V? I understand that 3V is the default when DK is powered by USB, but the VDD of my external boards is not 3V.

Some mention that it is not possible without the use of level shifters
 Programming using P19 external nrf5340 board powered at 1.8V 

Others say it is possible. To do that, the solder bridge SB19 on the nRF5340 DK must be shorted, so that the VDD of the external board is used as VIO_REF for debugging. 

  nRF5340-DK custom board flashing 1.8V 

 I can't program external board with nRF5340 2.0.2 

The board I have with nRF5340 SoC is battery powered and can have a VDD ranging from 3V to 1.8V. 

Can I short SB19 on the nRF5340 DK and have my external board supply VIO_REF to P19 for debugging?

[boxerwitness]

Yes, you can short SB19 on the nRF5340 DK to allow your external board's VDD (e.g., 1.8V) to supply VIO_REF for debugging, as long as the external board provides a stable VDD within the supported range (1.8V to 3.6V). This setup eliminates the need for level shifters for programming and debugging.

solar smash

[Joao Colombari]

Hi guys,

I have a few custom PCBs based on the nRF5340 and several peripheral ICs. One of these ICs has an absolute maximum supply voltage of 1.98 V. The boards do not include any external over-voltage protection.

For debugging, I have been using an nRF5340 DK as a J-Link probe, following the setup described here, with SB19 shorted so that the probe senses the target VDD level.

Several boards eventually developed a hard short between VDD and GND. After some investigation, I found that the failed component was the IC with the 1.98 V maximum supply rating. Once it was removed, SWD access to the nRF5340 was restored.

My question is: when using the DK as a debugger in this configuration, is there any possibility that the probe could briefly drive or expose the target to a higher voltage (e.g., 3.3 V) before it detects and adapts to the target VDD level?

I am trying to determine whether such a transient could explain the failures I observed.

Best regards,

João Colombari