In the USB3.2 Specification (Sept. 22, 2017) Table 6-18 and Table 6-22 give some characteristics for the TX and RX lines.
Basically, I understand that the TX lines have AC-Coupling capacitors to block DC and let just the AC signals pass. How is the min/max (75nF to 265nF) decided? What if my design has 10nF? Could this somehow effect USB3 enumeration?
The spec also mentions that having AC-Coupling on the RX lines is optional (because the device-side already has series capacitors on its Tx lines, which connect to the Host's Rx lines, so it isn't needed for DC blocking).
But it still states you can have up to ~330nF at the Rx side...I don't really get where this comes from.
This note states:
We recommend 330nF capacitors in order to meet the minimum capacitance requirement (75nF to 265nF) for RX detection.
I don't understand this note, and how having this capacitance can help with Rx detection...(I am working on a USB3 design where we are seeing some enumeration/fallback issues, and wondering if it might have something to do with these capacitance values)