LTE Module Series
EC20 Mini PCIe Hardware Design
EC20_Mini_PCIe_Hardware_Design Confidential / Released 19 / 36
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
shield them with surrounding ground.
In order to offer good ESD protection, it is recommended to add TVS. The 22R resistors should be
added in series between the module and USIM card so as to suppress the EMI spurious transmission
and enhance the ESD protection. The 33pF capacitors are used for filtering interference of
GSM850/EGSM900. Please note that the USIM peripheral circuit should be close to the USIM card
holder.
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 holder.
3.5. USB Interface
The following table shows the pin definition of USB interface.
Table 7: USB Pin Definition
EC20 Mini PCIe is compliant with USB 2.0 specification. It can only be used as a slave device. Meanwhile,
it supports high speed (480Mbps) and full speed (12Mbps) mode. The USB interface is used for AT
command, data transmission, GNSS NMEA output, software debug and firmware upgrade. The following
figure shows the reference circuit of USB interface.
Module
GND
MCU
Differential layout
USB_DM
GND
NM_2pF
VCC_MCU
VCC
USB_DP
USB_DM
USB_DP
Figure 5: Reference Circuit of USB Interface
Pin No.
Pin Name
I/O
Description
Comment
36
USB_DM
IO
USB differential data (-)
Require differential impedance of 90Ω
38
USB_DP
IO
USB differential data (+)
Require differential impedance of 90Ω
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