The nRF21540 DK has a 5 V boost regulator.
It gives a stable 5 V output from four possible sources:
- Universal Serial Bus (USB) connector J2 for the interface MCU
- USB connector J3 for the nRF52840
- Lithium-polymer (Li-poly) battery connectors (J6 or P27)
- VIN 3–5 V pin on P20
Each of these sources has a reverse protection diode to prevent current flowing in the wrong direction if multiple sources are connected at the same time.
Figure 1. 5V regulator and protecting diodes
