UMTS/HSDPA Module
UC15 Hardware Design
UC15_Hardware_Design Confidential / Released 42 / 72
1. Some AT commands are invalid when USIM card is not applied.
2. USIM card detection function is not supported currently.
If you do not need the USIM card detection function, keep USIM_PRESENCE unconnected. The
reference circuit for using a 6-pin USIM card socket is illustrated as the following figure.
Figure 24: Reference Circuit of the 6 Pin USIM Card
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:
z
Keep layout of USIM card as close as possible to the module. Assure the possibility of the length of
the trace is less than 20cm.
z
Keep USIM card signal away from RF and VBAT alignment.
z
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.
z
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away with each other and
shield them with surrounded ground.
z
In order to offer good ESD protection, it is recommended to add TVS such as WILL
(Ω
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 socket.
z
The pull-up resistor on USIM_DATA line can improve anti-jamming capability when long layout trace
and sensitive occasion is applied.
NOTES
