SIM900 Hardware Design
z Automatic acknowledge generation and checking
z Automatically generates Start repeated pattern when performing read operations
z Automatically observes and generates the acknowledge bit
z Implements a hardware assisted I2C-bus protocol
Table 22: Pin define of the I2C Bus
Note: This function is not supported in the default firmware. There must be customized firmware if you want.
Please contact SIMCom for more details.
4 Antenna Interface
SIM900 provides RF antenna interface. And customer’s antenna should be located in the customer’s main board
and connect to module’s antenna pad through microstrip line or other type RF trace which impendence must be
controlled in 50Ω. The Pin 60 is the RF antenna pad.
SIM900 material properties:
SIM900 PCB Material: FR4
Antenna pad: Gold plated pad
4.1 Module RF Output Power
Table 23: SIM900 conducted RF output power
Frequency Max Min
GSM850 33dBm ±2db 5dBm±5db
EGSM900 33dBm ±2db 5dBm±5db
DCS1800 30dBm ±2db 0dBm±5db
PCS1900 30dBm ±2db 0dBm±5db
4.2 Module RF Receive Sensitivity
Table 24: SIM900 conducted RF receive sensitivity
Frequency
Receive sensitivity（Typical）
Receive sensitivity(Max)
GSM850 -109dBm -107dBm
EGSM900 -109dBm -107dBm
DCS1800 -109dBm -107dBm
PCS1900 -109dBm -107dBm
Pin Name Pin Number Function
SCL 38 I2C Bus Clock
SDA 37 I2C Bus Data
SIM900_HD_V1.05 06.23.2010
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