Smart LTE Module Series
SC66 Hardware Design
SC66_Hardware_Design 62 / 139
Module
USIM_VDD
USIM_RST
USIM_CLK
USIM_ DATA
22R
22R
22R
100nF
ESD
22pF
VCC
RST
CLK
IO
VPP
GND
10K
USIM_VDD
22pF
22pF
R1
C1
D1
R2
R3
R4
C2
C3
C4
USIM_DET
(U)SIM Card Connector
Figure 20: Reference Circuit for (U)SIM Interface with a 6-pin (U)SIM Card Connector
In order to ensure good performance and avoid damage of (U)SIM cards, please follow the criteria below
in (U)SIM circuit design:
Keep placement of (U)SIM card connector as close to the module as possible. Keep the trace length
of (U)SIM card signals as less than 200mm as possible.
Keep (U)SIM card signals away from RF and VBAT traces.
A filter capacitor shall be reserved for USIM_VDD, and its maximum capacitance should not exceed
1uF. The capacitor should be placed near to (U)SIM card.
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
shield them with ground. USIM_RST also needs ground protection.
In order to offer good ESD protection, it is recommended to add a TVS diode array with parasitic
capacitance not exceeding 50pF
. The 22Ω resistors should be added in series between the module
and (U)SIM card so as to suppress EMI spurious transmission and enhance ESD protection. Please
note that the (U)SIM peripheral circuit should be close to the (U)SIM card connector.
The 22pF capacitors should be added in parallel on USIM_DATA, USIM_VDD, USIM_CLK and
USIM_RST signal lines so as to filter RF interference, and they should be placed as close to the
(U)SIM
card connector as possible.
3.12. SD Card Interface
SC66 module supports SD 3.0 specifications. The pin definition of the SD card interface is shown below.
Table 18: Pin Definition of SD Card Interface
Pin Name
Pin No.
I/O Description
Comment
