LTE-A Module Series
EG12 Hardware Design
EG12_Hardware_Design 47 / 97
It is important to route the USB 2.0 & 3.0 signal traces as differential pairs with total grounding. The
impedance of USB differential trace is
90Ω.
For USB 2.0 signal traces, the trace length should be less than 120mm, and the differential data pair
matching should be less than 2mm (15ps).
For USB 3.0 signal traces, the maximum length of each differential data pair (TX/RX) is
recommended to be less than 100mm, and each differential data pair matching should be less than
0.7mm (5ps).
Do not route signal traces under crystals, oscillators, magnetic devices, PCIe and RF signal traces. It
is important to route the USB differential traces in inner-layer of the PCB, and surround the traces
with ground on that layer and with ground planes above and below.
If a USB connector is used, please keep the ESD protection devices as close to the USB connector
as possible. Junction capacitance of the ESD protection device might cause influences on USB data
lines, so please pay attention to the selection of the device. Typically, the stray capacitance should
be less than 2.0pF for USB 2.0, and less than 0.4pF for USB 3.0.
If possible, reserve a 0
Ω resistor on USB_DP and USB_DM lines respectively.
“*” means under development.
3.11. UART Interfaces
The module provides three UART interfaces: main UART interface, debug UART interface, and BT UART
interface. Features of these interfaces are shown as below:
Main UART interface supports 4800bps, 9600bps, 19200bps, 38400bps, 57600bps, 115200bps
(default), 230400bps, 460800bps and 921600bps baud rates. This interface is used for data
transmission and AT command communication.
Debug UART interface supports 115200bps baud rate. It is used for Linux console and log output.
BT UART interface supports 115200bps baud rate. It is used for BT communication and can be
multiplexed into SPI interface*.
“*” means under development.
NOTE
NOTE