We are currently implementing the nRF52840 in an upcoming product and we have a question regarding component selection for our configuration.
I've looked through the datasheet and resources - our design most closely matches reference circuit #3 (QIAA footprint). We've matched the components to be populated and their respective values; however, in some instances we want to diverge from what is listed in the reference circuit BOM available on the site (attached for reference):
Notably, we want to use some capacitors that have different dielectrics than what is listed on the BOM. For example, we prefer to use X5R capacitors rather than the X7S/R listed for things like C21 and C6/C20. Is there any particular design consideration put into selecting the dielectrics on the reference BOM or can we change them?
Due to the summer vacations here in Norway we are currently short on staff, pardon the delay.
Changing to capacitors with different dielectrics should be OK, as long as the effective capacitance is within the specified limits. The effective capacitance is affected by AC and DC bias and temperature. For more information on the selection of decoupling capacitors please see our white paper on decoupling capacitor selection:
It does also include a section specifically on the nRF52840, including the effective capacitance specifications for the chip.