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⚫
The filter capacitor and ESD device of (U)SIM card signal cable should place close to the (U)SIM
card connector.
⚫
Please select equivalent capacitor is 22pF~33pF for ESD device.
⚫
USIM_DATA should pull up to USIM_VDD with a 10K resistor.
5.4 USB interface
5.4.1 USB Pin definition
Pin name
I/O
USB_DP
IO
USB_DM
IO
USB_VBUS
PI
For more information about the USB 2.0 specification, please refer to
Note:
Since the module supports USB 2.0 High-Speed, TVS tube equivalent capacitance on the USB_DM/DP
differential signal cable is required to be less than 1pF, and a 0.5pF capacitance TVS is recommended.
Connect a 0-ohm resistor to USB_DM / DP differential line to help analyze problems.
USB_DM and USB_DP are high-speed differential signal cables, can achieve the maximum transmission
rate of 480Mbits/s, and must follow the rules below in PCB Layout:
USB_DM and USB_DP signal cable's control differential impedance is 90 ohm
USB_DM and USB_DP signal cables shall be parallel and equal in length, and avoid the
right-angle route;
USB_DM and USB_DP signal cables are routed on the signal layer closest to the ground layer,
and the cables shall be grounded;
5.5 UART Interface
5.5.1 UART interface definition
NL668-LA series module has two serial ports: the main serial port and debug serial port. The main serial
ports support 4800bps, 9600bps, 19200bps, 38400bps, 57600bps, 115200bps, 230400bps baud rate.
The default baud rate is 115200bps, used for data transmission and AT command transmission.
Debug serial port support 115200bps baud rate for FIBOCOM internal debug. Table 5-8 and table 5-9 are
the pin definition of main serial port and debug serial port.
Reproduction forbidden without Fibocom Wireless Inc. written authorization - All Rights Reserved.
FIBOCOM NL668-LA Series Hardware User Manual
Pin Num.
69
70
71
Table 5- 9 USB Pin Definition
Description
USB differential data bus D+
USB differential data bus D-
USB Plug detect
http://www.usb.org/home
Page 37 of 65
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