Sim Card Design Guide - SIM Tech SIMCom SIM800C Hardware Design

Module
The SIM_DET pin is used for detection of the SIM card hot plug in. Customer can select the 8-pin SIM card
holder to implement SIM card detection function. AT command "AT+CSDT" is used to enable or disable SIM
card detection function. For details of this AT command, please refer to document [1].
If the SIM card detection function is not used, customer can keep the SIM_DET pin open. The reference circuit
of 6-pin SIM card holder is illustrated in the following figure.
Module
4.8.2.

SIM Card Design Guide

SIM card signal could be interferenced by some high frequency signal, it is strongly recommended to follow
these guidelines while designing:

SIM card holder should be far away from GSM antenna

SIM traces should keep away from RF lines, VBAT and high-speed signal lines

The traces should be as short as possible
 Keep SIM card holder's GND connect to main ground directly

Shielding the SIM card signal by ground well

Recommended to place a 100nF capacitor on SIM_VDD line and keep close to the SIM card holder

Add some TVS which parasitic capacitance should not exceed 50pF

Add 51Ω resistor to (SIM_RST/SIM_CLK/SIM_DATA) signal could enhance ESD protection
SIM800C_Hardware_Design_V1.00
4.7K
VDD_EXT
SIM_VDD
SIM_RST
SIM_CLK
SIM_DET
SIM_DATA
22pF
Figure 31: Reference circuit of the 8-pin SIM card holder
SIM_VDD
SIM_RST
SIM_CLK
SIM_DET
SIM_DATA
22pF
Figure 32: Reference circuit of the 6-pin SIM card holder
51R
51R
51R
100nF
SMF05C
51R
51R
C707 10M 006 512 2
51R
SMF05C
100nF
34
Smart Machine Smart Decision
MOLEX-91228
GND
VCC
VPP
RST
CLK I/O
PRESENCE GND
SIM Card
SIM Card
GND
VCC
VPP
RST
CLK I/O
2014-10-30