nRF52840 DK - Power Supply

[Nikosant03]

Hi everyone, I have a question related to the power supply of nRF52840 DK

I want to operate the nRF52840 DK with a LiPo battery (for experimental purposes). Is it possible at the same time to supply the board with the battery and have the USB connector connected to the PC?

Also, the external power supply is unregulated. Does this mean that the board will have the same potential everywhere as the external power supply?

Thanks in advance

Nick

[ketiljo]

The USB connection is not related to the power supply. So you can have the USB connection up while you power the device from another power source. If you want to power if from the USB connector, you must set the switch to USB.

See the HW description at_ infocenter.nordicsemi.com/.../hw_power_supply.html

[Nikosant03]

Hi ketiljo and thank you for your prompt response. I have read that in order to power up the board from the USB the switch (SW9) must be set to USB position. However, at the moment I have set the switch to VDD and the board works normally from the USB (J2), but it shouldn't work isn't it? So I am a bit confused...

[ketiljo]

That's normal. The USB connection to the nRF52840 is the other USB connector.

If you use J2, you will power the board from the USB connector so you can't use that together with the battery. Only the nRF USB can be used with the battery. But in that case, you will only have access to the nRF52840 USB interface and not the debugger

[Nikosant03]

Thanks for your reply. I have some questions so far:

1. Both programming and debugging of the firmware on nRF52840 SoC is done through the J2 USB connector and when the J2 connector is used the board is supplied from the 5V domain?

 

2. In order to power supply the nRF52840 SoC from the J3 I must toggle SW9 to USB isn’t it? I connect USB to J3 and toggle the switch to USB position, but the board is completely inactive. What is the purpose of J3 and how could I use it?

 

3. I want for example to supply the board with either 3.3V or 1.8V and measure the current consumption of nRF52840 SoC only. In that case, I must toggle the SW6 to nRF ONLY position and use the external power supply which is unregulated to supply either 3.3V or 1.8V. Ensure that the high voltage regulator is inactive meaning that VBUS, VBUS_nRF, Vli-Ion and VIN3-5V signals are low. If I want to include external's memory power consumption to the nRF52840 current measurement I must supply the external memory from VDD_nRF (short SB18 to connect memory power supply to VDD_nRF. Is this procedure correct?

 

4. If the boost regulator (high voltage regulator U12) is used, then the coin cell battery and the external power supply are ignored?

Thanks in advance

[ketiljo]

Nikosant03 said:

Both programming and debugging of the firmware on nRF52840 SoC is done through the J2 USB connector and when the J2 connector is used the board is supplied from the 5V domain?

 Yes, the debugger is connected to J2

 

Nikosant03 said:

In order to power supply the nRF52840 SoC from the J3 I must toggle SW9 to USB isn’t it? I connect USB to J3 and toggle the switch to USB position, but the board is completely inactive. What is the purpose of J3 and how could I use it?

 If you want to use the USB interface on the nRF52840, you must use J3. The switch J3 should be set to the USB position of you want the nRF52840 to be supplied from J3. 

From the PS: The nRF52840 System on Chip (SoC) has a high voltage buck regulator that can support up to 5 V input. In the VDD position, the SoC is powered either from the on-board buck regulator, coin cell battery, or external supply (P21). In the Li-Po position, the high voltage regulator of the SoC is supplied directly from the Li-Po battery connectors (J6 or P27). In the USB position, the USB high voltage regulator gets power from the nRF52840 USB connector (J3).

 

Nikosant03 said:

want for example to supply the board with either 3.3V or 1.8V and measure the current consumption of nRF52840 SoC only. In that case, I must toggle the SW6 to nRF ONLY position and use the external power supply which is unregulated to supply either 3.3V or 1.8V. Ensure that the high voltage regulator is inactive meaning that VBUS, VBUS_nRF, Vli-Ion and VIN3-5V signals are low. If I want to include external's memory power consumption to the nRF52840 current measurement I must supply the external memory from VDD_nRF (short SB18 to connect memory power supply to VDD_nRF. Is this procedure correct?

 Yes, that's correct.

 

Nikosant03 said:

If the boost regulator (high voltage regulator U12) is used, then the coin cell battery and the external power supply are ignored?

 Yes. The regulator U12 is supplied from VBUS, Li-ion input or the VIN, see the PS

[Nikosant03]

Thank you for your assistance!!

[Nikosant03]

Actually I have one more question. Can I supply the board from the VDD pins provided by P1 header?