NRF52840 logic level (3.3V) Available

[Vijil Jose]

I am using NRF52840 and supplying Li ion battery through VDDH.
I am getting 1.8V on GPIOs, SPI and uart.
When I connected VDD to Jlink, its upscaled to 3.3V (Since it is getting 3.3V through jlink).

I have connected some devices, where the connection is 3.3V.
Is there a way to operate NRF52840 on 3.3V logic?

[Jared]

Hi,

When using VDDH as input(High Voltage mode), VDD pin will be output, and the default voltage of VDD is 1V8. All GPIOs will always run at VDD voltage. You can change VDD output voltage by writing to the REGOUT0 register.

regards
Jared

[Vijil Jose]

can you give an example code for the same. also, all the SPI, UART voltage level also get changed by this correct?
Is there any advantage of running CPU in 1.8V compare to 3.3V?

[Jared]

Vijil Jose said:

can you give an example code for the same.

See this guide.

Vijil Jose said:

also, all the SPI, UART voltage level also get changed by this correct?

Yes, all GPIOs will run at VDD,

Vijil Jose said:

Is there any advantage of running CPU in 1.8V compare to 3.3V?

The CPU will not run on 3V3, only VDD, VDD will always be regulated down to 1V3 which is the system voltage:

regards

Jared 

[Vijil Jose]

Thanks for the info. So is there any efficiency advantage, if we keep the VDD same as 1.8V

[Jared]

Hi,

If you're using High voltage mode( HV mode) and supplying the nRF52840 with 3V3 from a battery then the efficiency whether the output from the REG0 regulator is 1V8 or 3V3 is not much in difference if you're using DC/DC for both REG0 and REG1.1V8 will be a tiny more efficient if you're only using DC/DC for one of the stages. But in the end, the digital voltage VDD should be chosen based on the VDD of external components. 

regards

Jared