nRF52840-QIAA Noisy VDD supply

[sammy91]

Hi there, I am using the MDBT50Q-1MV2 Raytac module, with the nRF52840, and i have noticed that I have a very noisy VDD supply pin. Which definitely a problem because measures very small voltages and is very sensitive to noise.

I have an external 3V LDO:

and I have tied VDD and VDDH together to disable Reg0:

Also, I have noticed that by, adding:

sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);

causes VDD to change the noise to a 5mV 'chopping' triangle wave noise, but then depending on device operation jumps up to 15mV noise.

So my question is:

What connection + firmware arrangement for my nRF will provide the most stable VDD supply voltage (<1mV noise)?

Power consumption is not an issue.

[Turbo J]

You will have to redesign your PCB.

Looking at the electrical specifications, RADIO will consume up to about 30mA when running - and since softdevice turns this only on when used, there will be significant steps in current consumtion.

It is probably advisable to use a second LDO for powering external measuring circuitry in order to separate the voltage rail from the noisy NRF supply.

You can try to reduce the noise a bit by disabling the DCDC and not use the power saving feature. But the radio will still generate above mentioned current consumtion steps.