Using nRF5340-PDK at 3.3V instead of 1.8V

RE: Using nRF5340-PDK at 3.3V instead of 1.8V

DBT — Fri, 12 Jun 2020 16:31:38 GMT

Well, I could have sworn that I was measuring 1.8V before I tried making changes, but when I erase UICR and put SW9 back to "VDD" and remove the power at P27, then I'm measuring VDD at 3.0V and VDDnRF_HV at 3.0V.

I confirmed with an nRF5340-PDK new out of the box.

So it sounds like rather than adjusting UICR registers I want to change the 3.0V regulator to 3.3V.

U11 is the regulator and if I change R60 from 330k to 375k then that should give 3.3V

I didn't have a 375k resistor in an 0201 package, but was able to make a 374k in 0402 package work

Now VDD measures 3.3V

So I guess this is the way to do it if you don't want to use a separate supply (no UICR changes needed, but you need to modify the board)

Let me know if there's a better way to do this for using J2 power only.

RE: Using nRF5340-PDK at 3.3V instead of 1.8V

Jørgen Holmefjord — Thu, 11 Jun 2020 14:07:53 GMT

Are you able to get 1.8 V GPIO output when running from J2 USB connector? I believe this will always go through the onboard 3 V buck regulator and power the nRF5340 through the VDD pin in Normal voltage mode. As described in GPIO levels, the GPIO voltage can only be configured when running in high-voltage mode:

"In normal voltage mode, the GPIO high level equals the voltage supplied to the VDD pin. In high voltage mode, it equals the level specified in the VREGHVOUT register."

RE: Using nRF5340-PDK at 3.3V instead of 1.8V

DBT — Thu, 11 Jun 2020 13:15:35 GMT

OK that works if I connect a 5V power supply to P27 (Li-Po) and change SW9 to Li-Po.

Is there a way to do it using only the power from the micro-USB connector J2?

RE: Using nRF5340-PDK at 3.3V instead of 1.8V

Jørgen Holmefjord — Thu, 11 Jun 2020 11:15:32 GMT

Hi,

It should be sufficient to write the VREGHOUT UICR register:

nrfjprog --family nrf53 --memwr 0x00FF8010 --val 5

I tested this on the DK, and it sets the GPIO output to 3.3V when running from 5V power source.

Note that if you have previously written 0 to this register, you need to do an eraseall operation before you can write it again:

nrfjprog --family nrf53 --memwr 0x00FF8010 --val 5
Parsing parameters.
Writing.

nrfjprog --family nrf53 --memrd 0x00FF8010
0x00FF8010: 00000005                              |....|

nrfjprog --family nrf53 --memwr 0x00FF8010 --val 7
Parsing parameters.
ERROR: The area to write is not erased.

nrfjprog --family nrf53 -e
Erasing user available code and UICR flash areas.
Applying system reset.

nrfjprog --family nrf53 --memwr 0x00FF8010 --val 5
Parsing parameters.
Writing.

Best regards,
Jørgen