Does opening VDD pin when nRF5340 High voltage mode is available? (VDD not used)

[gwan0624]

Hello,

I am planning to use the nRF5340 in High Voltage mode and LDO mode. Currently, I am designing a PCB where minimizing the component count is critical.

I understand that in High Voltage mode, the VDD pin functions as a voltage output. However, I do not intend to use the VDD pin to supply power to any external circuits. Under these circumstances, the decoupling capacitors around the VDD pin seem unnecessary.

My main question is:

Is it acceptable to leave the VDD pins completely open (floating)?

Or is it mandatory to place capacitors between VDD and GND for regulator stability, even if there is no external load?

Thank you.

[Szabolcs]

Hi Minseok,

Yes, you still need these capacitors unfortunately, as they are needed to decouple the internal voltage supply of the nRF. Also, these pins need to be connected on the PCB to each other. (Please see configuration 4 in the reference circuitry.)

[gwan0624]

(CLAA reference 4, as suggested)

(CLAA reference 4 pcb)

Thank you for the clarification.

I checked the reference circuitry, and I realize that each VDD pin indeed requires its own capacitor. It is unfortunate for my space constraints, but I accept that they are necessary.

While I now understand that the VDD capacitors are mandatory, could you confirm if I can remove R1 (on VBUS) and C16 (on DECUSB)?

- I do not intend to use the USB interface/power at all.

- My system will be powered solely by a 3.3V input to VDDH.

(I found a Q&A post—linked below—stating that these components can be omitted, but since the post is 6 years old, I would like to verify if this is still applicable to the nRF5340.)

 nRF5340 regulator inductors 

[Szabolcs]

Yes, you can. Connect VBUS to GND, and leave DECUSB NC. See Configuration 3 for example.

[gwan0624]

Thank you so much Szabolcs, Your advice was really helpful!