nRF52840 DCDC mode DCDC switching frequency?

[Poki Huang]

Hi:

Since we have a issue that when nRF52840 setting to DCDC mode, our inductive touch will have bigger noise, if setting to LDO mode, the inductive touch noise disappear

So could you help check what the nRF52840 DCDC switching frequency(same like nRF52832 8MHz)?  What the tolerance of this frequency? Can we tuning it?

Thank you~~

Poki

[Poki Huang]

Hi 

I add one question

Will this switching frequency coupling to other trace?

If  yes, do you have suggestion layout that can avoid it?

Thank you~~

Poki

[ketiljo]

The DCDC switching frequency is fixed at 8 MHz. The energy can couple to other traces if they run near the inductors. 

[Poki Huang]

Hi Ketijo:

Seems we check the noise is radiate out to the inductive coil, not couple on board

So do you have any suggestion that can improve this radiation, like how layout can improve it? Or any else?

Thank you~~

Poki 

[ketiljo]

Try to separate the touch input lines as much as you can from the DCDC inductors. Ground plane between the two as well.

[hmolesworth]

Maybe try a shielded indictor if not already using one; that would radiate less.