Product Info

LTE Module Series
EG21-G MINIPCIE Hardware Design
EG21-G_MINIPCIE_Hardware_Design 20 / 48
If (U)SIM card detection function is not needed, please keep USIM_PRESENCE unconnected. A
reference circuit for (U)SIM interface with a 6-pin (U)SIM card connector is illustrated in the following
figure.
USIM_VDD
GND
USIM_RST
USIM_CLK
USIM_DATA
0R
0R
0R
100nF
GND
33pF 33pF 33pF
VCC
RST
CLK IO
VPP
GND
GND
15K
USIM_VDD
(U)SIM Card Connector
Module
Figure 5: Reference Circuit of (U)SIM Interface with a 6-Pin (U)SIM Card Connector
In order to enhance the reliability and availability of the (U)SIM card in customers’ applications, please
follow the criteria below in (U)SIM circuit design:
 Keep placement of (U)SIM card connector to the module as close as possible. Keep the trace length
as less than 200mm as possible.
 Keep (U)SIM card signals away from RF and power supply traces.
 Assure the ground trace between the module and the (U)SIM card connector short and wide. Keep
the trace width of ground and USIM_VDD no less than 0.5mm to maintain the same electric potential.
Make sure the bypass capacitor between USIM_VDD and USIM_GND is less than 1uF, and be
placed 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 with parasitic
capacitance not exceeding 15pF. The 0Ω resistors should be added in series between the module
and the (U)SIM card so as 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.