nrf52840 Vbus supply and supplying external components with 3.3v

[Callum Little]

I am using the nrf52840 on the Raytac MDBT50Q-1MV2 module. (https://www.raytac.com/product/ins.php?index_id=24)

I am supplying the module with 5v USB power to the VBUS pin. I need a standard 3v3 output from the module to power external components and I am using VDD for this purpose. However, when I provide power to the chip the VDD is not outputting 3v3. What setup do I need in order to get a 3v3 output from the module/chip in order to supply external components?

Thank you.

[Jared]

Hi,

I am supplying the module with 5v USB power to the VBUS pin.

This would only supply the USB interface, unless VDDH is already tied to VBUS?

regards

Jared 

[Callum Little]

Hi,

So in order to use VDD as a 3v3 output, VDDH must be tied to the 5v at VBUS?

[Jared]

To use VDD for external supply you would have to configure the nRF52840 in High Voltage mode. HVM is configured by supplying the nRF52840 only through VDDH. VBUS does not supply the nRF52840, it only supplies the USB interface which has its own power domain. If power is only connected trough the VBUS then you'll have to tie VDDH and VBUS together so VDDH is also supplied. See this section in the product specification.

regards

Jared 

[Callum Little]

Great!

Thank you for your help.

[Callum Little]

Hi, VDDH is now tied to VBUS at 5v but when measuring VDD, the output still reads as about 0v.

What other steps must I take in order to use VDD as a 3v3 supply for external components?

Thank you.

-Callum

[Jared]

And you're measuring 5V on VDDH? Can you disconnect any signal that is connected to VDD and measure the voltage on VDDH and VDD again? VDD is the output of REG0 and should be set when you supply VDDH in High Voltage mode. Note that VDDH and VDD should not be tied together in this configuration. Also, are you using DC/DC or LDO mode for REG0?

[Callum Little]

Yes, we are measuring 5V on VDDH. We are using the nrf on a PCB so we do not have the opportunity to disconnect any connected signals to VDD. VDDH and VDD are not tied together in our configuration. I believe we are using LDO mode for REG0.

Thanks.

[Jared]

Hi,

Can you share the schematics for your design?

regards

Jared