Product Info

Smart LTE Module Series
SC20 Hardware Design
SC20_Hardware_Design 48 / 130
USIM_VDD
USIM_RST
USIM_CLK
USIM_ DATA
USIM_DET
22R
LD05_1V8
100K
100nF
(U)SIM Card Connector
ESD
33pF
VCC
RST
CLK
IO
VPP
GND
USIM_VDD
10K
Module
R1
R2
C1
33pF33pF
C2 C3 C4
D1
22R
22R
R3
R4
R5
Figure 17: Reference Circuit for (U)SIM Interface with an 8-pin (U)SIM Card Connector
If there is no need to use USIM_DETECT, please keep it open. The following is a reference circuit for
(U)SIM interface with a 6-pin (U)SIM card connector.
Module
USIM_VDD
USIM_RST
USIM_CLK
USIM_DATA
22R
22R
22R
100nF
(U)SIM card connector
ESD
33pF
VCC
RST
CLK IO
VPP
GND
10K
USIM_VDD
33pF
33pF
R1
C1
D1
R2
R3
R4
C2 C3 C4
Figure 18: 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 100nF 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.