Sd Card Interface - Quectel SC66 Hardware Design

USIM_ VDD
USIM_ RST
USIM_ CLK
Module
USIM_ DET
USIM_ DATA
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

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
SC66_Hardware_Design
USIM _VDD
R1
C1
10K
100nF
22R
R2
R3
22R
22R
R4
C2 C3 C4
22pF 22pF 22pF
(U)SIM card.
Description Comment
Smart LTE Module Series
SC66 Hardware Design
(U)SIM Card Connector
VCC GND
RST VPP
CLK IO
D1
ESD
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