Series Resistor on VBUS

[Arielle]

Hi! Do people actually use the 2.2-4.7Ohm series resistor on the VBUS input to the nRF5340? It's just such a low resistance, I don't particularly see the point. Thanks!

[Turbo J]

Look at the reference circuit schematics, the resistor is part of a low pass filter. The resistor may be tiny but the capacitor is not.

USB cables have a (small) inductivity and thus interesting (high frequency) behaviour when plugging/unplugging the cable. That high frequency noise can't make it past the low pass filter.

[Ressa]

Hi,

Yes it is being used. As Jörg also mentioned the resistor should be considered with the large cap next to it which together acts like a low pass filter to prevent voltage overshoot/ undershoot. 

[Arielle]

Makes sense, thank you!