M12 Hardware Design
M12_Hardware_Design_V3.3 - 52 -
Module
SIM_VDD
SIM_RST
SIM_CLK
SIM_DATA
SIM_PRESENCE
22R
22R
22R
100nF
SIM_Holder
GND
ESDA6V8V6
33pF
33pF 33pF 33pF
GND
GND GND
VCC
RST
CLK IO
VPP
GND
Figure 34: Reference circuit of the 6 pins SIM card
In SIM interface designing, in order to ensure good communication performance with SIM card,
the following design principles should be complied with.
Place the SIM card holder close to module as close as possible. Ensure the trace length of
SIM signals do not exceed 200mm.
Keep the SIM signals far away from VBAT power and RF trace.
The width of SIM_VDD trace is not less than 0.5mm. Place a bypass capacitor close to SIM
card power pin. The value of capacitor is less than 1uF.
To avoid possible cross-talk from the SIM_CLK signal to the SIM_DATA signal be careful
that both lines are not placed closely next to each other. So each of SIM_DATA and
SIM_CLK line should be shield by ground. For good performance, the SIM_RST line also
should be protected by the ground.
In order to ensure good ESD protection, it is recommended to add TVS such as WILL
(http://www.willsemi.com) ESDA6V8AV6. The capacitance of ESD component is less than
50pF. The 22Ω resistors should be added in series between the module and the SIM card so
as to suppress the EMI spurious transmission and enhance the ESD protection. Note that the
SIM peripheral circuit should be close to the SIM card socket.
Place the RF bypass capacitors (33pF) close to the SIM card on all signals line for improving
EMI.
3.10.2. SIM card holder
For 6-pin SIM card holder, it is recommended to use Amphenol C707 10M006 512 2. Please visit
http://www.amphenol.com for more information
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