Original question:
Our TUSB1142 design uses the Flip signal from a TPS25820 to switch the superspeed signals from a Type C connector. We are not able to get Superspeed to work at all. Once the Flip signal was disconnected, one of the two sets of Superspeed signals does enumerate to Superspeed. What is happening when the Flip signal is disconnected to cause the one channel to enumerate to Superspeed?
The schematic is attached.
Hi,
The issue here is that the TPS25820 POL is an open drain signal. The POL open-drain logic output that signals which Type-C CC pin is connected to the cable CC line. This gives the information needed to mux the super speed lines. Asserted (driving low) when the CC2 pin is connected to the cable CC line. And when CC2 pin is connected, SSTX2/SSRX2 is the USB path.
But for TUSB1142, when FLIP pin is driving low, SSTX1/SSRX1 is the USB path, so there is a mismatch between the two devices.
To solve this issue, you need to swap the CC1 and CC2, connect CC1 from the Type-C connector to TPS25820 CC2, and connect CC2 from the Type-C connector to TPS25820 CC1.
Also, for SSTX1 and SSTX2, please use 0.22uF instead 0.33uF.
Thanks
David
