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LTE Standard Module Series
EG91 Series Hardware Design
EG91_Series_Hardware_Design
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•
Make sure the bypass capacitor between USIM_VDD and USIM_GND less than 1uF, and place it as
close to (U)SIM card connector as possible. If the ground is complete on customers’ PCB,
USIM_GND can be connected to PCB ground directly.
•
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
shield them with surrounded ground.
•
In order to offer good ESD protection, it is recommended to add a TVS diode array whose parasitic
capacitance should not be more than 15pF. The 0Ω resistors should be added in series between the
module and the (U)SIM card to facilitate debugging. The 33pF capacitors are used for filtering
interference of EGSM900. Please note that the (U)SIM peripheral circuit should be close to the
(U)SIM card connector.
•
The pull-up resistor on USIM_DATA line can improve anti-jamming capability when long layout trace
and sensitive occasion are applied, and should be placed close to the (U)SIM card connector.
3.10.
USB Interface
EG91 series module contains one integrated Universal Serial Bus (USB) interface which complies with
the USB 2.0 specification and supports high-speed (480Mbps) and full-speed (12Mbps) modes. The USB
interface acts as slave only, and is used for AT command communication, data transmission, GNSS
NMEA sentences output, software debugging, firmware upgrade and voice over USB. The following table
shows the pin definition of USB interface.
Table 10: Pin Definition of USB Interface
Pin Name
Pin No.
I/O
Description
Comment
USB_DP
9
IO
USB differential data bus (+)
Require differential
impedance of 90Ω.
USB_DM
10
IO
USB differential data bus (-)
Require differential
impedance of 90Ω.
USB_VBUS
8
PI
USB connection detection
Typical: 5.0V
GND
3
Ground
For more details about USB 2.0 specifications, please visit http://www.usb.org/home.
The USB interface is recommended to be reserved for firmware upgrade in customers’ design. The
following figure shows a reference circuit of USB interface.