Smart Machine Smart Decision
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 64 kbps 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
SIM_VDD
16
Voltage supply for SIM card. Support 1.8V or 3V SIM card
SIM_DATA
14
SIM data input/output
SIM_CLK
55
SIM clock
SIM_RST
15
SIM reset
SIM_DET
54
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. That the SIM peripheral circuit should be close to the SIM card socket.
The reference circuit of the 8-pin SIM card holder is illustrated in the following figure.
SIM800H&SIM800L_Hardware Design_V2.02 38
2015-07-27
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
51Ω
51Ω
51Ω
