Design Considerations For Usim Card Holder - Quectel UC15 Hardware Design

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 200mm.

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_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 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 capacitance of ESD component is less than 50pF.
The 22Ω 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. The 33pF capacitors are
used for filtering interference of 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 is applied.
3.13.2.

Design Considerations for USIM Card Holder

For 8-pin USIM card holder, it is recommended to use Molex 91228. Please visit http://www.molex.com for
more information.
UC15_Hardware_Design
Figure 31: Reference Circuit of the 6-Pin USIM Card
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