Can supply power through VDD and VBUS together?

[moon.kim]

Hi,

I want to use external power (battery) and USB power together.

If USB is not connected, I want to supply it with battery power, and if USB is connected, I want to supply power through VBUS.

Is it possible to use it like this?

Chip :nRF52820

SDK 17.0.2

I made a custom board based on the circuit diagram below. 

infocenter.nordicsemi.com/.../ref_circuitry.html

[Andreas]

Hi,

 

No you can not, the recommended VDD and VBUS does not overlap: https://infocenter.nordicsemi.com/topic/ps_nrf52820/recommended_op_conditions.html?cp=4_3_0_7

 

VBUS only powers the USB circuitry, which is only needed when the USB cable is attached, the rest of the IC is powered by VDD. VBUS is designed to be powered by the 5V bus rail provided by the USB host.

 

Best regards,
Andreas

[moon.kim]

hi.

Then, if I use this circuit, can I use external power and USB power as I said?

I want to supply power to the battery source(VDD) and supply it to VBUS when the USB is connected.

infocenter.nordicsemi.com/index.jsp

[Andreas]

Hi,

 

Unfortunately no. You can power VDDH from VBUS for a design that will only be powered on when USB is connected (see circuit 1). You can not power VBUS from VDDH or VDD.

 

You do not need to supply VBUS from the battery as it will be provided by the USB host when USB is connected.

 

Best regards,
Andreas

[moon.kim]

Hi.

Sorry. My question is very confusing. I got the question wrong.

When the USB cable is connected, I want to run the MCU without consuming battery current.

In the case of circuit 1, does the MCU operate only with USB power?

[Andreas]

Hi,

 

In circuit 1 the MCU operates only with USB power. If you want the MCU to no consume battery power when plugged into USB you need a PMIC or switch circuit that disconnects the battery from the MCU, and connects the USB power. Note that USB will have to be provided to VDDH, so you need to make sure that the battery voltage is inside the supported range for VDDH.

 

Best regards,
Andreas