RAK4630 Schematic VDD_NRF Question

WisBlock
1

Hi guys,

Not sure if this is the right place to ask this, but I’m working on a design with the RAK4630 module. Wondering if I can have some clarification, below is the schematic for the RAK4631

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In the power section, there are two unpopulated 0 ohm resistors (I’ve highlighted them in yellow). These resistors would connect VDD_NRF to 3V3 and/or VBAT_IO_SX. Without these resistors VDD_NRF is left floating. I have confirmed that these resistors are not populated on the modules I have.

In the RAK4630 datasheet, it mentions to connect VDD_NRF to 3V3 if using a single 3.3V power supply or connect VDD_NRF and VBAT_IO_SX together in a battery setup.

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Since the RAK4631 connects VDD_NRF to neither 3V3 or VBAT_IO_SX was it determined that this is not necessary?

Thanks,
Zander

2

The RAK4630 module should be supplied as shown on the RAK4631 with two voltages, a 3.3V supply and a higher second voltage for the DCDC converter of the nRF52840.

Single supply voltage requires a change on the RAK4630, but the component (L10) is under the metal hood, so it cannot be done easy.

3

Thanks Beegee,

We will be powering the RAK4630 with both 5V via VBUS and 3.3V via VBAT_NRF, VBAT_SX and VAT_IO_SX. Can you confirm if VDD_NRF should be connected to 3.3V?

L10 on the RAK4630 schematic shows it as NC so I would be skeptical if it’s actually populated? All the resistors labeled as NC are not populated.

4

On my schematics (same as n the Doc Center) L10 is populated and it is connected to the internal DCDC of the nRF52840.

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For your configuration, follow the suggested connections of the RAK4631

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VDD_NRF is created in the module by the DCDC, that’s why it is left open

5

I was mistaking as L10 is also a designator on the RAK4631 and thought you were referring to it.

Yes it would make sense to not connect VDD_NRF to the 3V3 but was looking for clarification.

Thanks for the help Beegee!