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24
Hardware Development Guide
ME3616
Figure 2-13 reference design of USIM interface
In order to enhance the reliability and availability of the USIM card in customer’s application, please follow
the following criterion in the USIM circuit design:
Keep layout of USIM card as close as possible to the module. Assure the possibility of the length of the
trace is less than 50mm.
Keep USIM card signal away from RF and VBAT alignment.
Assure the ground between module and USIM cassette short and wide. Keep the width of ground and
USIM_VCC no less than 0.5mm to maintain the same electric potential. The decouple capacitor of
USIM_VCC should be less than 1uF and must be near to USIM cassette.
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away with each other and shield
them with surrounded ground.
In order to offer good ESD protection, it is recommended to add TVS such as WILL
(http://www.willsemi.com) ESDA6V8AV6. The 33Ω resistors should be added in series between the
module and the USIM card so as to suppress the EMI spurious transmission and enhance the ESD
protection. Please note that the USIM peripheral circuit should be close to the USIM card socket.
The pull-up resistor on USIM_DATA line can improve anti-jamming capability when long layout trace
and sensitive occasion is applied.
2.10.2.
D
ESIGN
C
ONSIDERATIONS FOR
USIM
C
ARD
H
OLDER
For 8-pin USIM card holder, it is recommended to use Molex 91228.
Please visit http://www.molex.com for more information.