Are 3.3pF caps needed on PB10, PB11, and PC5 (sensitive GPIOs) if they are not connected to anything?

FAdar.1 · ‎2021-02-25

This is for the STM32WB5MMG, on page 11/31 of the datasheet.

Remi QUINTIN · ‎2021-02-26

If PB10, PB11, and PC5 are no connected, the 3.3pF are not needed.

It is only when tracks are connected to those 3 sensitive pins that the capacitors are recommended to avoid propagation of noise along the board.

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Vangelis Fortounas · ‎2021-02-25

Hello

why not connect it to GND?

3p3 capacitance (reactance is 20 ohms) is too low and makes someone to suspect that theese three GPIOs are succeptible to 2.4GHz causing various, observed already effects

Remi QUINTIN · ‎2021-02-26

If PB10, PB11, and PC5 are no connected, the 3.3pF are not needed.

It is only when tracks are connected to those 3 sensitive pins that the capacitors are recommended to avoid propagation of noise along the board.