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FIBOCOM FG621-LA Series Hardware Guide
Page 34 of 57
The USIM_DET pin is active high by default, and can be switched to active low by AT command.
Table 5-8 USIM_DET effective level switched
AT command
Function description
AT+GTSET=”SIMPHASE”,1
Default, high level detection
AT+GTSET=”SIMPHASE”,0
Low level detection
5.3.4 (U)SIM Design Requirements
(U)SIM card circuit design should meet EMC standards and ESD requirements, and at the same time,
should improve anti-interference ability to ensure that the (U)SIM card can work stably. The design needs
to strictly follow the following rules:
(U)SIM card connector is placed as close to the module as possible, away from the RF antenna,
DCDC power, clock signal lines and other strong interference sources.
It is recommended to use (U)SIM card connector with metal shielding shell to improve
anti-interference ability.
The length of signal line from the module to the (U)SIM card connector should not exceed 100mm.
Longer signal line reduces signal quality.
USIM_CLK and USIM_DATA signals should be ground protected to avoid mutual interference. If it is
difficult to do so, (U)SIM signals need to be ground protected as a set.
The filter capacitor and ESD device of (U)SIM card signal line should be placed close to the (U)SIM
card connector.
The total capacitance of ESD equivalent capacitor and parallel capacitor should be less than 47pF.
USIM_DATA should be pulled up to USIM_VDD with a 10K resistor.
5.4 USB Interface
FG621-LA series modules support USB2.0, and are compatible with USB High-Speed (480Mbits/s) and
USB Full-Speed (12Mbits/s). Refer to the “Universal Serial Bus Specification 2.0” for USB Bus timing and
electrical characteristics of modules. USB pin definition is as follow:
Table 5-9 USB pin definition
Pin Name
I/O
Pin#
Description
USB_DP
IO
34
USB differential data +
USB_DM
IO
33
USB differential data -
USB_VBUS
PI
32
USB Plug detect
For more information about the USB 2.0 specification, please visit
http://www.usb.org/home
.
Note:
