Quectel SC690A Series, Hardware Design

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Smart Module Series
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The module supports (U)SIM card hot-plug via the USIM_DET pin, which is disabled by default and can
be enabled through software configuration. A reference circuit for (U)SIM interface with an 8-pin (U)SIM
card connector is shown below.
Module
USIM_VDD
(U)SIM Card Connector
USIM_RST
USIM_CLK
USIM_DATA
USIM_DET
GND
SIM_RST
SIM_CLK
SIM_DATA
SIM_DET
GND
SIM_VDD
100 K 10 K
C1
C2
C3
C4
ESD
LDO9_1V8
USIM_VDD
R3
R4
R5
R1
R2
22 R
22 R
22 R
22 pF 22 pF 22 pF
100 nF
Figure 15: Reference Circuit of (U)SIM Interface with an 8-Pin (U)SIM Card Connector
To enhance the reliability and availability of the (U)SIM card in applications, please follow the criteria
below in (U)SIM circuit design.
⚫
Keep (U)SIM card connector as close as possible to the module. Keep the trace length as less than
200 mm as possible.
⚫
Keep (U)SIM card signal traces away from RF and VBAT traces.
⚫
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
shield them with ground surrounded.
⚫
For better ESD protection, it is recommended to add a TVS diode array with a parasitic capacitance
not exceeding 50 pF. The 22
Ω resistors should be added in series between the module and the
(U)SIM card connector to suppress EMI spurious transmission and enhance ESD protection.
⚫
The pull-up resistor on USIM_DATA trace improves anti-jamming capability and should be placed
close to the (U)SIM card connector.
⚫
Add 22 pF capacitors parallel on USIM_DATA, USIM_CLK and USIM_RST signal traces to filter RF
interference, and place them as close to the
(U)SIM
card connector as possible.