Hardware Design V1.01(091226)

SIM900 Hardware Design
Contents
Contents .....................................................................................................................................................................3
Version history...........................................................................................................................................................7
1 Introduction.............................................................................................................................................................8
1.1 Related Documents .......................................................................................................................................8
1.2 Terms and Abbreviations...............................................................................................................................8
2 SIM900 Overview.................................................................................................................................................12
2.1 SIM900 Key Features..................................................................................................................................12
2.2 SIM900 Functional Diagram.......................................................................................................................14
2.3 SIM900 Evaluation Board...........................................................................................................................15
3 Application Interface.............................................................................................................................................16
3.1 SIM900 Pin Description..............................................................................................................................16
3.2 Operating Modes.........................................................................................................................................19
3.3 Power Supply ..............................................................................................................................................20
3.3.1 Power Supply Pins.............................................................................................................................22
3.3.2 Minimizing Power Losses .................................................................................................................22
3.3.3 Monitoring Power Supply .................................................................................................................22
3.4 Power Up and Power Down Scenarios........................................................................................................22
3.4.1 Turn on SIM900 ................................................................................................................................22
3.4.2 Turn Off SIM900...............................................................................................................................25
3.4.3 Restart SIM900 Using the PWRKEY Pin .........................................................................................28
3.5 Power Saving ..............................................................................................................................................28
3.5.1 Minimum Functionality Mode ..........................................................................................................28
3.5.2 Sleep Mode (Slow Clock Mode) .......................................................................................................29
3.5.3 Wake Up SIM900 from SLEEP Mode..............................................................................................29
3.6 Summary of State Transitions (except SLEEP mode).................................................................................29
3.7 RTC Backup ................................................................................................................................................29
3.8 Serial Interfaces...........................................................................................................................................31
3.8.1 Function of serial port & debug port supporting ...............................................................................33
3.8.2 Software Upgrade and Software Debug ............................................................................................33
3.9 Audio Interfaces ..........................................................................................................................................35
3.9.1 Speaker Interface Configuration........................................................................................................35
3.9.2 Microphone Interfaces Configuration ...............................................................................................36
3.9.3 Earphone Interface Configuration .....................................................................................................37
3.9.4 Referenced Electronic Characteristic ................................................................................................37
3.10 SIM Card Interface....................................................................................................................................38
3.10.1 SIM Card Application .....................................................................................................................38
3.10.2 Design Considerations for SIM Card Holder ..................................................................................39
3.11 LCD Display Interface ..............................................................................................................................42
3.12 Keypad Interface .......................................................................................................................................42
SIM900_HD_V1.01 26.12.2009
3