USB power supply and additional external power supply

Question

Hello, 
 in my application I want to power the nRF52840 with USB at the VBUS pin or a 3.3V external supply at the VDD pin. 
 I wonder what will happen if someone plugs in both, that there is supply at VBUS and VDD? 
 Thank you. 
 Adrian

Marjeris Romero · Accepted Answer

Hi Adrian, 
 Take a look at the reference circuit for nRF2840 at the infocenter for guidelines in how to power the nRF52840. If you want to power using 5V from USB you need to connect VBUS voltage to the VDDH pin (as shown in config nr 1). VDD can then be used as an external voltage supply VEXT to power other things in your circuit. You will then run the chip in high voltage mode. If you want to power from a 3.3V battery or external power supply you need to connect 3.3V to both VDD and VDDH pin, see config nr. 3. You cannot power the chip with 5V USB and 3.3V at the same time, since VDD will act as an external power supply in high voltage mode. 
 Best Regards, 
 Marjeris

USB power supply and additional external power supply

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