Smart Machine Smart Decision
SIM800C_Hardware_Design_V1.02
32
2015-4-27
M odule
P R E S E N C E
100nF
M O LE X -91228
S IM C ard
22pF
V C C
G N D
R S T
V P P
C LK
I/O
G N D
V D D _E X T
S IM _V D D
S IM _R S T
S IM _C LK
S IM _D A T A
4.7K
E S D A 6V 1
S IM _D E T
51Ω
51Ω
51Ω
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
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.
M odule
S IM C ard
V C C
G N D
R S T
V P P
C LK
I/O
C 707 10M 006 512 2
22pF
100nF
S IM _V D D
S IM _R S T
S IM _C LK
S IM _D A T A
S IM _D E T
E S D A 6V 1
51Ω
51Ω
51Ω
Figure 31: Reference circuit of the 6-pin SIM card holder
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 51
Ω
resistor to (SIM_RST/SIM_CLK/SIM_DATA) signal could enhance ESD protection
4.8.3.
Design Considerations for SIM Card Holder
For 8 pins SIM card holder, SIMCom recommends to use Molex 91228.Customer can visit
http://www.molex.com
for more information about the holder.
