Usim Card Interface - Quectel EC25 Hardware Design

3.4. USIM Card Interface

The following table shows the pin definition of USIM card interface.
Table 6: USIM Pin Definition
Pin No. Pin Name
8 USIM_VDD
10 USIM_DATA
12 USIM_CLK
14 USIM_RST
EC25 Mini PCIe supports 1.8V and 3.0V USIM cards. The following figure shows a reference design for a
6-pin USIM card connector.
Module
GND
USIM_VDD
USIM_RST
USIM_CLK
USIM_DATA
Figure 4: Reference Circuit of USIM Card Interface with a 6-Pin USIM Card Connector
In order to enhance the reliability and availability of the USIM card in your application, please follow the
criteria below in USIM circuit design:

Keep layout of USIM card as close to the module as possible. Keep the trace length as less than
200mm as possible.

Keep USIM card signal away from RF and power supply traces.

Keep the trace width of ground and USIM_VDD no less than 0.5mm to maintain the same electric
potential. The decouple capacitor of USIM_VDD should be less than 1uF and must near to USIM
card connector.
EC25_Mini_PCIe_Hardware_Design
I/O Power Domain
PO 1.8V/3.0V
IO 1.8V/3.0V
DO 1.8V/3.0V
DO 1.8V/3.0V
USIM_VDD
15K
22R
22R
22R
33pF 33pF33pF 33pF
GND
Confidential / Released
LTE Module Series
EC25 Mini PCIe Hardware Design
Description
Power source for the USIM card
USIM data signal
USIM clock signal
USIM reset signal
100nF
USIM Card Connector
VCC GND
RST VPP
CLK IO
GND
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