User's Manual

Smart Machine Smart Decision
SIM868_Hardware_Design_V1.00 35 2016-06-20
Conducting noise is mainly caused by the VBAT drop. If audio PA was powered by VBAT directly, then there
will be some cheep noise from speaker output easily. So it is better to put big capacitors and ferrite beads near
audio PA input.
TDD noise has something to do with GND signal. If GND plane is not good, lots of high-frequency noises will
interference microphone and speaker over bypass capacitor. So a good GND during PCB layout could avoid
TDD noise.
4.8. SIM Card Interface
The SIM interface complies with the GSM Phase 1 specification and the new GSM Phase 2+ specification for
FAST 64kbps SIM card. Both 1.8V and 3.0V SIM card are supported. The SIM interface is powered from an
internal regulator in the module.
4.8.1. SIM Card Application
Table 17: SIM pin definition
Pin name
Pin number Function
SIM1_VDD 18 Voltage supply for SIM card. Support 1.8V or 3V SIM card
SIM1_DATA 15 SIM data input/output
SIM1_CLK 16 SIM clock
SIM1_RST 17 SIM reset
SIM1_DET 14 SIM card detection
SIM2_VDD 56 Voltage supply for SIM card. Support 1.8V or 3V SIM card
SIM2_DATA 53 SIM data input/output
SIM2_CLK 54 SIM clock
SIM2_RST 55 SIM reset
SIM2_DET 52 SIM card detection
It is recommended to use an ESD protection component such as ST (www.st.com ) ESDA6V1-5W6 or ON
SEMI (www.onsemi.com ) SMF05C. The SIM card peripheral components should be placed close to the SIM
card holder. The reference circuit of the 8-pin SIM card holder is illustrated in the following figure.
Module
PRESENCE
100nF
MOLEX-91228
SIM Card
22pF
VCC
GND
RST
VPP
CLK I/O
GND
VDD_EXT
SIM_VDD
SIM_RST
SIM_CLK
SIM_DATA
4.7K
ESDA6V1
SIM_DET
51O
51O
22pF
51O
22pF
Figure 30: Reference circuit of the 8-pin SIM card holder
The SIM_DET pin is used for detection of the SIM card hot plug in. Customer can select the 8-pin SIM card