20
/
50
It is important to route the USB 2.0&3.0 signal traces as differential pairs with total grounding.
1)
For USB 2.0 routing traces, the trace impedance of a differential pair should be 90Ω, and the
length matching of the differential pair should be less than 2mm.
2)
For USB 3.0 routing traces, the trace impedance of Tx and Rx differential pairs should be 90Ω,
and the length matching of Tx and Rx differential pairs should be less than 0.7mm.
Do not route signal traces under crystals, oscillators, magnetic devices or RF signal traces. It is
important to route the USB 2.0&3.0 differential traces in inner-layer with ground shielding on not only
upper and lower layers but also right and left sides.
If USB connector is used, please keep the ESD protection components to the USB connector as
close as possible. Pay attention to the influence of junction capacitance of ESD protection
components on USB 2.0&3.0 data lines. The capacitance value of ESD protection components
should be less than 2.0pF for USB 2.0, and less than 0.4pF for USB 3.0.
If possible, reserve a 0R resistor on USB_D+ and USB_D- lines.
“*” means under development.
3.6.
PCM and I2C Interfaces
The following table shows the pin definition of PCM and I2C interfaces that can be applied in audio codec
design.
Table 8: Pin Definition of PCM and I2C Interfaces
Pin No. Pin Name
I/O
Power
Domain
Description
Comment
45
PCM_CLK
IO
1.8V
PCM clock signal
47
PCM_DOUT
DO
1.8V
PCM data output
49
PCM_DIN
DI
1.8V
PCM data input
51
PCM_SYNC
IO
1.8V
PCM frame synchronization
30
I2C_SCL
DO
1.8V
I2C serial clock
Require external pull-up to
1.8V.
32
I2C_SDA
IO
1.8V
I2C serial data
Require external pull-up to
1.8V.
NOTE
S
