USB 3.0 Hub Design Guide
© 2015 Genesys Logic, Inc. - All rights reserved.
Page 12
GLI Confidential
2.3.8
Avoid Stub on Differential Traces
Please avoid unexpected stubs. If the Test Pin is needed to be put on the differential pair trace, please make sure
there is no stub on any signal trace. (as shown in
Fig. 2.9
)
Good Layout:
Avoid Stub
Test Pad
Bad Layout
Test Pad
Figure 2.9
2.3.9
SS Trace Swap
If cross trace is needed to make the layout easier, SS differential trace (TXP /TXN or RXP / RXN) N&P can be
swapped. As shown in
Fig 2.10
-
Pin TXN of the IC can be connected to TXP of the connector.
-
Pin TXP of the IC can be connected to TXN of the connector.
-
Pin RXN of the IC can be connected to RXP of the connector.
-
Pin RXP of the IC can be connected to RXN of the connector.
Figure 2.10
Note:
1.
Because some devices may not support RXN/RXP swap function, it is
NOT
recommended swap Hub
TXN and TXP traces for better compatibility.
2.
If TXN and TXP swap function is needed for layout concern, Hub firmware needs to be modified
accordingly. The “TXP/N Swap” function
MUST
be selected in Configuration of the Genesys Logic USB
3.0 Hub FW ISP Tool at the same time. Choose the port whose TXN and TXP traces is swapped. (as
shown in
Fig 2.11
)