SimCom SIM900

SIM900 Reference Design Guide Notes
SIM900_AN_Reference Design Guide_V1.01 01.27.2010
3
Contents
Version history..................................................................................................................................4
1. Introduction...................................................................................................................................5
1.1 References Document ..........................................................................................................5
2 Application Interface......................................................................................................................2
2.1 Power Supply Design...........................................................................................................2
2.1.1 VBAT design ..............................................................................................................2
2.1.2 Battery Charge design ................................................................................................3
2.1.3 PWRKEY ON/OFF design.........................................................................................4
2.1.4 Reset design................................................................................................................5
2.1.5 RTC backup design ....................................................................................................5
2.2. UART interface ...................................................................................................................5
2.2.1 UART interface design ...............................................................................................5
2.3 GPIO selection .....................................................................................................................6
2.3.1 STATUS and NETLIGHT ..........................................................................................6
2.3.2 GPIO...........................................................................................................................7
2.4 Audio interfaces ...................................................................................................................7
2.4.1 Referenced circuit of headset design ..........................................................................8
2.4.2 Referenced circuit of hand free design.......................................................................8
2.5 Antenna matching circuit design ..........................................................................................8
2.6 SIM card interface................................................................................................................9
2.7 ESD protection ...................................................................................................................10
2.8 Consideration in PCB layout..............................................................................................10