Smart Module Series
SC200K_Series_Hardware_Design 49 / 105
Module
USIM _VDD
USIM_ RST
USIM _ CLK
USIM _DATA
22 R
22 R
22 R
1
μF
ESD
33 pF
VCC
RST
CLK
IO
VPP
GND
33 pF
33 pF
C 1
D 1
R 2
R 3
R 4
C 2
C 3
C 4
USIM _ DET
(U)SIM Connector
20K
R 1
GND
Figure 19: Reference Circuit of (U)SIM Interfaces with 6-Pin (U)SIM Card Connector
To ensure the reliability and availability of the (U)SIM card in applications, follow the criteria below in the
(U)SIM circuit design:
⚫
Place the (U)SIM card connector as close to the module as possible. Keep the trace length as less
than 200 mm as possible.
⚫
Keep (U)SIM card signals away from RF and VBAT traces.
⚫
Reserve a filter capacitor for USIM_VDD, and its maximum
capacitance should not exceed 1 μF.
Additionally, place the capacitor near the
(U)SIM
card connector.
⚫
To avoid cross-talk between USIM_DATA and USIM_CLK, keep them away from each other and
shield them with surrounded ground.
⚫
In order to offer better ESD protection, it is recommended to add a TVS component with a parasitic
capacitance not exceeding 50 pF. The 22 Ω resistors should be connected in series between the
module and the (U)SIM card to facilitate debugging. Connect 33 pF capacitors in parallel on
USIM_DATA, USIM_CLK and USIM_RST signal lines to filter RF interference. Additionally, keep the
(U)SIM peripheral circuit as close to the (U)SIM card connector as possible.
⚫
The pull-up resistor on USIM_DATA circuit can improve anti-jamming capability of the (U)SIM card. If
the (U)SIM card traces are too long, or the interference source is relatively close, it is recommended
to add a pull-up resistor near the (U)SIM card connector.
