Hardware description
Since it is only the nRF5340 SoC that is supplied from this source, it is recommended to supply the VDD
domain from a different source to prevent the pins of the SoC to be connected to unpowered devices.
To avoid voltage differences on the board, the External supply is also connected to the input of the voltage
follower when SW10 is in the ON position. The voltage follower circuit requires 5 V to be present on the
board, see section 5 V power sources on page 14.
The voltage follower can be disconnected from the External supply by cutting SB58. To prevent leakage
due to voltage differences, the board should be set in the nRF only mode, see section Operating modes on
page 19.
Note: To reduce trace length and parasitic components, the external memory is connected to the
SoC directly instead of using analog switches. It is recommended to cut solder bridges to avoid
leakage, see section External memory on page 21.
5.4 Operating modes
The nRF5340 PDK board has various modes of operation.
5.4.1 USB detect
To detect when USB for the interface MCU is connected, there is a circuit sensing the VBUS of USB
connector J2.
When the USB cable is connected, the VDD is propagated to the USB_DETECT signal.
Figure 15: USB detect
5.4.2 nRF only mode
The nRF only mode disconnects the power supply of the interface MCU, the external memory, and the
LEDs as well as disconnects the signal lines between the nRF5340 SoC and the interface MCU using analog
switches.
This is done to isolate the chip on the board as much as possible, and can be of use when measuring
currents on low-power applications.
The power supply of the external memory can be changed to maintain operation in the nRF only mode.
See section External memory on page 21.
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