Power configuration 4 and external DCDC

RE: Power configuration 4 and external DCDC

Tiit — Tue, 22 Oct 2024 06:07:57 GMT

No .. I actually mean, if I need to put some additional pull-up or down for some GPIO line that has no external resistor and same component already has external resistor on some other GPIO line.

I have strange current leak on my custom board -- I have SPI e-paper, that is powered from external DCDC. Our board configuration is so, that MCU internal DCDC output has nothing connected (only SWD socket for programming, because NRF52840 from factory has 1.8V VDD and I can't flash it straight from the box with DK without powering the MCU with 3V from SWD socket).

If I flash the board, then e-paper gets power from somewhere and is active. Therefore I tought that some internal pull-up is maybe giving parasitic power via SPI or something like that.

RE: Power configuration 4 and external DCDC

Bendik Heiskel — Mon, 21 Oct 2024 14:50:42 GMT

Using both internal and external pull-up or pull-down at the same time is not recommended. The internal ones should be disabled when using external ones.

RE: Power configuration 4 and external DCDC

Tiit — Mon, 21 Oct 2024 06:45:44 GMT

Ok .. good, but when I use with example nr. 4 internal pull-up / pull-down mixed with external .. would that be OK?

RE: Power configuration 4 and external DCDC

Bendik Heiskel — Fri, 18 Oct 2024 13:04:10 GMT

Hi,

There's no issue using external DCDC converter for the other components on the board, but you need to make sure the VDD voltage of the nRF52840 is the same as the external DCDC.

By default, when using REG0 with VDDH as the supply for the SoC, the VDD voltage will be 1.8V, if you want to use another voltage for the external components and pullups, you need to change the output voltage of REG0 using the UICR register REGOUT0

If the external DCDC converter can supply enough current, it is easiest to change to configuration 5 and supply the nRF52840 from the external DCDC.

Best regards,

Bendik