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sim900 hardware design document title: SIM900A hardware design version: 1.01 date: 2009-12-26 status: release document control id: SIM900A_hd_v1.01 general notes simcom offers this information as a service to its customers, to support application and engineering efforts that use the products designed by simcom. the information provided is based upon requirements specifically provided to simcom by the customers. simcom has not undertaken any independent search for additional relevant information, including any info rmation that may be in the customer?s possession. furthermore, system validation of this product designed by simcom within a larger electronic system remains the responsibility of the customer or the cust omer?s system integrator. all specifications supplied herein are subject to change. copyright this document contains proprietary technical information which is the property of simcom limited, copying of this document and giving it to others and th e using or communication of the contents thereof, are forbidden without express authority. offenders are liable to the payment of damages. all rights reserved in the event of grant of a patent or the registration of a utility model or design. all specification supplied herein are subject to change without notice at any time. copyright ? shanghai simcom wireless solutions ltd. 2009 sim900_hd_v1.01 26.12.2009 2 free datasheet http://www..net/
sim900 hardware design contents contents ............................................................................................................................... ......................................3 version history ............................................................................................................................... ............................7 1 introduction ............................................................................................................................... ..............................8 1.1 related documents ............................................................................................................................... ........8 1.2 terms and abbreviations ............................................................................................................................... 8 2 SIM900A overview ............................................................................................................................... ...............13 2.1 SIM900A key features ............................................................................................................................... 13 2.2 SIM900A functional diagram ....................................................................................................................15 2.3 SIM900A evaluation board ........................................................................................................................16 3 application interface ............................................................................................................................... ..............17 3.1 SIM900A pin description ...........................................................................................................................17 3.2 operating modes ............................................................................................................................... ..........20 3.3 power supply ............................................................................................................................... ...............21 3.3.1 power supply pins .............................................................................................................................22 3.3.2 minimizing power losses .................................................................................................................23 3.3.3 monitoring power supply .................................................................................................................23 3.4 power up and power down scenarios ........................................................................................................23 3.4.1 turn on SIM900A .............................................................................................................................23 3.4.2 turn off SIM900A ............................................................................................................................26 3.4.3 restart SIM900A using the pwrkey pin ......................................................................................28 3.5 power saving ............................................................................................................................... ...............29 3.5.1 minimum functionality mode ..........................................................................................................29 3.5.2 sleep mode (slow clock mode) .......................................................................................................29 3.5.3 wake up sim9 00a from sleep mode ...........................................................................................30 3.6 summary of state trans itions (except sleep mode) .................................................................................30 3.7 rtc backup ............................................................................................................................... .................30 3.8 serial interfaces ............................................................................................................................... ............32 3.8.1 function of serial port & debug port supporting ...............................................................................33 3.8.2 software upgrade and software debug ............................................................................................34 3.9 audio interfaces ............................................................................................................................... ...........35 3.9.1 speaker interface configuration ........................................................................................................36 3.9.2 microphone interfaces configuration ...............................................................................................37 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 ..................................................................................40 3.11 lcd display interface ..............................................................................................................................4 2 3.12 keypad interface ............................................................................................................................... ........42 sim900_hd_v1.01 26.12.2009 3 free datasheet http://www..net/
sim900 hardware design 3.13 adc ............................................................................................................................... ...........................43 3.14 behaviors of the ri ............................................................................................................................... ....44 3.15 network status indication .........................................................................................................................45 3.16 general purpose input output (gpio) ......................................................................................................46 3.17 external reset ............................................................................................................................... ............47 3.18 pwm ............................................................................................................................... ..........................47 3.19 i2c bus ............................................................................................................................... .......................47 4 antenna interface ............................................................................................................................... ...................48 4.2 module rf output power ...........................................................................................................................48 4.3 module rf receive sensitivity ...................................................................................................................48 4.4 module operating frequencies ...................................................................................................................49 5 electrical, reliability and radio characteristics ...................................................................................................49 5.1 absolute maximum ratings ........................................................................................................................49 5.2 operating temperatures ..............................................................................................................................4 9 5.3 power supply ratings ............................................................................................................................... ..50 5.4 current consumption ............................................................................................................................... ...50 5.5 electro-static discharge ..............................................................................................................................5 1 6 mechanics ............................................................................................................................... ..............................52 6.1 mechanical dimensions of SIM900A .........................................................................................................52 6.2 top and bottom view of the SIM900A .......................................................................................................54 6.3 pin assignment of SIM900A .....................................................................................................................55 6.4 the ramp-soak-spike reflow profile of SIM900A ...................................................................................57 sim900_hd_v1.01 26.12.2009 4 free datasheet http://www..net/
sim900 hardware design table index table 1: related documents ............................................................................................................................... 8 table 2: terms and abbreviations ................................................................................................................... 8 table 3: SIM900A key features ........................................................................................................................... 13 table 4: coding schemes and maximum net data rates over air interface ............................ 15 table 5: pin description ............................................................................................................................... ........ 17 table 6: overview of operating modes ........................................................................................................ 20 table 7: pin definition of the serial interfaces .................................................................................... 32 table 8: logic levels of the serial port and debug port ................................................................. 32 table 9: pin define of the audio interface ................................................................................................ 35 table 10: mic input characteristics ............................................................................................................. 38 table 11: audio output characteristics .................................................................................................... 38 table 12: pin define of the sim interface .................................................................................................... 38 table 13: pin description (a mphenol sim card holder) ...................................................................... 40 table 14: pin description (molex sim card holder) .............................................................................. 41 table 15: pin define of the lcd interface ................................................................................................... 42 table 16: pin define of the keypad interface ........................................................................................... 42 table 17: adc specification ............................................................................................................................... .44 table 18: behaviours of the ri .......................................................................................................................... 44 table 19: working state of the netlight ................................................................................................... 45 table 20: pin define of the gpio interface ................................................................................................. 46 table 21: pin define of the pwm ........................................................................................................................ 47 table 22: pin define of the i2c bus .................................................................................................................. 48 table 23: SIM900A conducted rf output power ........................................................................................ 48 table 24: SIM900A conducted rf receive sensitivity ............................................................................ 48 table 25: SIM900A operating frequencies .................................................................................................... 49 table 26: absolute maximum ratings ........................................................................................................... 49 table 27: SIM900A operating temperature .................................................................................................. 49 table 28: SIM900A power supply ratings ....................................................................................................... 50 table 29: SIM900A current consumption ...................................................................................................... 50 table 30: the esd endure statue measured table (temperature: 25 , humidity:45% ) ........ 51 table 31: pin assignment ............................................................................................................................... ....... 55 sim900_hd_v1.01 26.12.2009 5 free datasheet http://www..net/
sim900 hardware design figure index figure 1: SIM900A functional diagram ......................................................................................................... 15 figure 2: top view of SIM900A evb .................................................................................................................... 16 figure 3: reference circu it of the vbat input ........................................................................................ 21 figure 4: reference circuit of the source power supply input ..................................................... 22 figure 5: vbat voltage drop during transmit burst ........................................................................... 22 figure 6: turn on SIM900A using driving circuit ..................................................................................... 24 figure 7: turn on SIM900A using button ...................................................................................................... 24 figure 8: timing of turn on system using pwrkey ................................................................................ 24 figure 9: turn on SIM900A using driving circuit ..................................................................................... 25 figure 10: turn on SIM900A using button .................................................................................................... 25 figure 11: timing of turn on system using pwrkey and pwrkey_out ......................................... 26 figure 12: timing of turn off system using pwrkey ............................................................................. 27 figure 13: timing of turn off system using pwrkey and pwrkey_out ........................................ 27 figure 14: timing of restart system ............................................................................................................. 29 figure 15: state transition ............................................................................................................................... .30 figure 16: rtc supply from non-chargeable battery ......................................................................... 30 figure 17: rtc supply from rechargeable battery .............................................................................. 31 figure 18: rtc supply from capacitor .......................................................................................................... 31 figure 19: seiko xh414h-iv01e charge characteristic ......................................................................... 31 figure 20: connection of the serial interfaces ..................................................................................... 33 figure 21: connection of software upgrade and software debug ............................................. 34 figure 22: rs232 le vel converter circuit ................................................................................................... 35 figure 23: speaker interface configuration ........................................................................................... 36 figure 24: speaker interface with amplifier configuration .......................................................... 36 figure 25: micro phone interface configuration ................................................................................... 37 figure 26: earphone in terface configuration ........................................................................................ 37 figure 27: reference circuit of the 8 pins sim card .............................................................................. 39 figure 28: reference circuit of the 6 pins sim card .............................................................................. 39 figure 29: amphenol c707 10m006 512 2 sim card holder ........................................................................ 40 figure 30: molex 91228 sim card holder ...................................................................................................... 41 figure 31: reference circuit of the keypad interface ....................................................................... 43 figure 32: architecture of adc ....................................................................................................................... 43 figure 33: SIM900A services as receiver ....................................................................................................... 44 figure 34: SIM900A services as caller ........................................................................................................... 45 figure 35: reference circuit of netlight .................................................................................................. 46 figure 36: reset timing ............................................................................................................................... .......... 47 figure 37: top an side mechanical dimensions of module unit: mm .................................... 52 figure 38 bottom mechanical dimensions of module unit: mm ......................................... 53 figure 39: recommended pcb decal unit: mm .................................................................................... 53 figure 40: top view of the SIM900A .................................................................................................................. 54 figure 41: SIM900A pin out diagram (top view) .......................................................................................... 55 figure 42: the ramp-soak-spike reflow profile of SIM900A ............................................................... 57 sim900_hd_v1.01 26.12.2009 6 free datasheet http://www..net/
SIM900A hardware design version history date version description of change author 2009-12-26 1.01 origin ligang SIM900A_hd_v1.01 7 26.12.2009 free datasheet http://www..net/
sim900 hardware design 1 introduction this document describes the hardware interface of the simcom SIM900A module that connects to the specific application and the air interface. as si m900a can be integrated with a wide range of applications, all functional components of SIM900A are described in great detail. this document can help you quickly understand SIM900A interface specifications, electrical and mechanical details. with the help of this document and other SIM900A application notes, user guide, you can use SIM900A module to design and set-up mobile applications quickly. 1.1 related documents table 1 : related documents sn document name remark [1] SIM900A_atc SIM900A_atc [2] itu-t draft new recommendation v.25ter: serial asynchronous automatic dialing and control [3] gsm 07.07: digital cellular telecommunications (phase 2+); at command set for gsm mobile equipment (me) [4] gsm 07.10: support gsm 07.10 multiplexing protocol [5] gsm 07.05: digital cellular telecommunications (phase 2+); use of data terminal equipment ? data circuit terminating equipment (dte ? dce) interface for short message service (sms) and cell broadcast service (cbs) [6] gsm 11.14: digital cellular telecommunications system (phase 2+); specification of the sim application toolkit for the subscriber identity module ? mobile equipment (sim ? me) interface [7] gsm 11.11: digital cellular telecommunications system (phase 2+); specification of the subscriber identity module ? mobile equipment (sim ? me) interface [8] gsm 03.38: digital cellular telecommunications system (phase 2+); alphabets and language-specific information [9] gsm 11.10 digital cellular telecommunications system (phase 2) mobile station (ms) conformance specification part 1: conformance specification [10] an_serial port an_serial port 1.2 terms and abbreviations table 2 : terms and abbreviations sim900_hd_v1.01 26.12.2009 8 free datasheet http://www..net/
sim900 hardware design abbreviation description adc analog-to-digital converter amr adaptive multi-rate arp antenna reference point asic application specific integrated circuit ber bit error rate bts base transceiver station chap challenge handshake authentication protocol cs coding scheme csd circuit switched data cts clear to send dac digital-to-analog converter drx discontinuous reception dsp digital signal processor dte data terminal equipment (typically computer, terminal, printer) dtr data terminal ready dtx discontinuous transmission efr enhanced full rate egsm enhanced gsm emc electromagnetic compatibility esd electrostatic discharge ets european telecommunication standard fcc federal communications commission (u.s.) fdma frequency division multiple access fr full rate gmsk gaussian minimum shift keying gprs general packet radio service gsm global standard for mobile communications hr half rate i/o input/output ic integrated circuit imei international mobile equipment identity abbreviation description kbps kilo bits per second led light emitting diode li-ion lithium-ion mo mobile originated ms mobile station (gsm engine), also referred to as te sim900_hd_v1.01 26.12.2009 9 free datasheet http://www..net/
sim900 hardware design mt mobile terminated pap password authentication protocol pbcch packet switched broadcast control channel pcb printed circuit board pdu protocol data unit ppp point-to-point protocol rf radio frequency rms root mean square (value) rtc real time clock rx receive direction sim subscriber identification module sms short message service tdma time division multiple access te terminal equipment, also referred to as dte tx transmit direction uart universal asynchronous receiver & transmitter urc unsolicited result code ussd unstructured supplementary service data vswr voltage standing wave ratio vmax maximum voltage value vnorm normal voltage value vmin minimum voltage value vihmax maximum input high level voltage value vihmin minimum input high level voltage value vilmax maximum input low level voltage value vilmin minimum input low level voltage value vimax absolute maximum input voltage value vimin absolute minimum input voltage value vohmax maximum output high level voltage value vohmin minimum output high level voltage value volmax maximum output low level voltage value volmin minimum output low level voltage value inorm normal current imax maximum load current phonebook abbreviations abbreviation description fd sim fix dialing phonebook ld sim last dialing phonebook (list of numbers most recently dialed) sim900_hd_v1.01 26.12.2009 10 free datasheet http://www..net/
sim900 hardware design mc mobile equipment list of unansw ered mt calls (missed calls) on sim (or me) own numbers (msisdns) list rc mobile equipment list of received calls sm sim phonebook nc not connect 1.3 safety caution the following safety precautions must be observed during all phases of the operation. usage, service or repair of any cellular terminal or mobile incorporating SIM900A module. manufactures of the cellular terminal should send words the following safety information to users and operating personnel and to incorporate these guidelines into all manuals supplied with the product. if not so, simcom does not take on any liability for customer failure to comply with these precautions. when in a hospital or other health care facility, observe the restrictions about the use of mobiles. switch the cellular terminal or mobile off, medical equipment may be sensitive to not operate normally for rf energy interference. switch off the cellular terminal or mobile before boarding an aircraft. make sure it be switched off. the operation of wireless appliances in an ai rcraft is forbidden to pr event interference with communication systems. forget to th ink much of these instructions may lead to the flight safety or offend against local legal action, or both. do not operate the cellular terminal or mobile in the presence of flammable gases or fumes. switch off the cellular terminal when you are near petrol stations, fu el depots, chemical plants or where blasting operations are in progress. oper ation of any electrical equipment in potentially explosive atmospheres can constitute a safety hazard. your cellular terminal or mobile receives a nd transmits radio frequency energy while switched on. rf interference can occur if it is used close to tv sets, radios, computers or other electric equipment. road safety comes first! do not use a hand-held cellular terminal or mobile when driving a vehicle, unless it is securely mounted in a holder for hands free operation. before making a call with a hand-held terminal or mobile, park the vehicle. sim900_hd_v1.01 26.12.2009 11 free datasheet http://www..net/
sim900 hardware design gsm cellular terminals or mobiles operate over radio frequency signals and cellular networks and cannot be guaranteed to connect in all cond itions, for example no mobile fee or a invalid sim card. while you are in this condition and need emergent help, please remember using emergency calls. in order to make or receive calls, the cellular terminal or mobile must be switched on and in a service area with adequate cellular signal strength. some networks do not allow for emergency call if certain network services or phone features are in use (e.g. lock functions, fixed dialing etc.). you may have to deactivate those features before you can make an emergency call. also, some networks require that a valid sim card be properly inserted in the cellular terminal or mobile. sim900_hd_v1.01 26.12.2009 12 free datasheet http://www..net/
sim900 hardware design 2 SIM900A overview designed for global market, sim900 a is a dual-band gsm/gprs engine that works on frequencies egsm 900mhz and dcs 1800mhz. SIM900A features gprs multi-sl ot class 10/ class 8 (optional) and supports the gprs coding schemes cs-1, cs-2, cs-3 and cs-4. with a tiny configuration of 24mm x 24mm x 3mm, SIM900A can meet almost all the space requirements in your applications, such as m2m, smart phone, pda and other mobile devices. the physical interface to the mobile application is a 68-pin smt pad, which provides all hardware interfaces between the module and customers? boards. z the keypad and spi display interface will give you the flexibility to develop customized applications. z serial port and debug port can help you easily develop your applications. z one audio channel includes a microph one input and a sp eaker output. z programmable general purpose input & output. the SIM900A is designed with power saving technique so that the current consumption is as low as 1.5ma in sleep mode. the SIM900A is integrated with the tcp/ip protocol; extended tcp/ip at commands are developed for customers to use the tcp/ip protocol easily, which is very useful for those data transfer applications. 2.1 SIM900A key features table 3 : SIM900A key features feature implementation power supply single supply voltage 3.4v ? 4.5v power saving typical power consumption in sleep mode is 1.5ma ( bs-pa-mfrms=5 ) frequency bands z SIM900A dual-band: egsm900, dcs1800. the SIM900A can search the 2 frequency bands automatically. the frequency bands also can be set by at command. z compliant to gsm phase 2/2+ gsm class small ms transmitting power z class 4 (2w) at egsm 900 z class 1 (1w) at dcs 1800 gprs connectivity z gprs multi-slot class 10 default z gprs multi-slot class 8 (option) z gprs mobile station class b sim900_hd_v1.01 26.12.2009 13 free datasheet http://www..net/
sim900 hardware design temperature range z normal operation: -30c to +80c z restricted operation: -40c to -30c and +80 c to +85c (1) z storage temperature -45c to +90c data gprs: csd: z gprs data downlink transfer: max. 85.6 kbps z gprs data uplink transfer: max. 42.8 kbps z coding scheme: cs-1, cs-2, cs-3 and cs-4 z supports the protocols pap (password authentication protocol) usually used for ppp connections. z integrates the tcp/ip protocol. z support packet switched broad cast control channel (pbcch) z csd transmission rates: 2.4, 4.8, 9.6, 14.4 kbps, non-transparent z unstructured supplementary services data (ussd) support sms z mt, mo, cb, text and pdu mode z sms storage: sim card fax group 3 class 1 sim interface support sim card: 1.8v, 3v external antenna antenna pad audio features speech codec modes: z half rate (ets 06.20) z full rate (ets 06.10) z enhanced full rate (ets 06.50 / 06.60 / 06.80) z adaptive multi rate (amr) z echo cancellation z noise suppression serial port and debug port serial port: z 8-wire modem interface with status and control lines, unbalanced, asynchronous. z 1.2kbps to 115.2kbps. z serial port can be used for at commands or data stream. z supports rts/cts hardware handshake and software on/off flow control. z multiplex ability according to gsm 07.10 multiplexer protocol. z autobauding supports baud rate from 1200 bps to 115200bps. debug port: z 2-wire null modem interface dbg_txd and dbg_rxd. z can be used for debugging and upgrading firmware. phonebook management support phonebook types: sm, fd, ld, rc, on, mc. sim application toolkit support sat class 3, gsm 11.14 release 99 real time clock implemented timer function programmable via at command physical characteristics size: 24mm x 24mm x 3mm weight: 3.4g firmware upgrade firmware upgrade by debug port. sim900_hd_v1.01 26.12.2009 14 free datasheet http://www..net/
sim900 hardware design (1) the SIM900A does work, but deviations from the gsm specification may occur. table 4 : coding schemes and maximum ne t data rates over air interface coding scheme 1 timeslot 2 timeslot 4 timeslot cs-1: 9.05kbps 18.1kbps 36.2kbps cs-2: 13.4kbps 26.8kbps 53.6kbps cs-3: 15.6kbps 31.2kbps 62.4kbps cs-4: 21.4kbps 42.8kbps 85.6kbps 2.2 SIM900A functional diagram the following figure shows a functional diagram of the SIM900A and illustrates the mainly functional part: z the gsm baseband engine z flash and sram z the gsm radio frequency part z the antenna interface z the other interfaces figure 1: SIM900A functional diagram sim900_hd_v1.01 26.12.2009 15 free datasheet http://www..net/
sim900 hardware design 2.3 SIM900A evaluation board in order to help you on the application of SIM900A, simcom can supply an evaluation board (evb) that interfaces the SIM900A directly with appropriate power s upply, sim card holder, rs232 serial port, handset port, earphone port, line in port, antenna and all gpio of the SIM900A. figure 2: top view of SIM900A evb for details please refer to the SIM900A-evb_ugd document. sim900_hd_v1.01 26.12.2009 16 free datasheet http://www..net/
sim900 hardware design 3 application interface SIM900A is equipped with a 68-pin smt pad that connect s to the cellular application platform. sub-interfaces included in these smt pads are described in detail in following chapters: z power supply ( please refer to chapter 3.3 ) z serial interfaces (please refer to chapter 3.8 ) z analog audio interfaces ( please refer to chapter 3.9 ) z sim interface ( please refer to chapter 3.10 ) electrical and mechanical characteristi cs of the smt pad are specified in chapter 5. 3.1 SIM900A pin description table 5 : pin description power supply pin name i/o description dc characteristics comment vbat i 3 vbat pins are dedicated to connect the supply voltage. the power supply of SIM900A has to be a single voltage source of vbat= 3.4v...4.5v. it must be able to provide sufficient current in a transmit burst which typically rises to 2a vmax= 4.5v vmin=3.4v vnorm=4.0v vrtc i/o current input for rtc when the battery is not supplied for the system. current output for backup battery when the main battery is present and the backup battery is in low voltage state. vmax=3.15v vmin=2.0v vnorm=3.0v iout(max)= 300ua iin=2 ua if the rtc function is enabled, a battery or capacitor should be connected with the vrtc pin. otherwise the vrtc pin can be keep open. vdd_ext o 2.8v output power supply vmax=2.95v vmin=2.70v vnorm=2.80v if unused, keep open. sim900_hd_v1.01 26.12.2009 17 free datasheet http://www..net/
sim900 hardware design iout(max)= 10ma gnd ground power on or power off pin name i/o description dc characteristics pwrkey i voltage input for pwrkey. pwrkey should be pulled low to power on or power off the system. the user should keep pressing the key for a short time when power on or power off the system because the system need margin time in order to assert the software. vilmax=0.15*vdd_ext vihmin=0.85* vdd_ext vimax=vdd_ext vilmin= 0v it is already pulled up. pwrkey_o ut o connecting pwrkey and pwrkey_out for a short time then release also can power on or power off the module. vohmin= vdd_ext-0.1v volmax=0.1v vohmax= vdd_ext volmin= 0v audio interfaces pin name i/o description dc characteristics comment mic_p mic_n i positive and negative voice band input audio dc characteristics refer to chapter 3.9 if unused keep open spk_p spk_n o positive and negative voice band output if unused keep open linein_r linein_l i line input if unused keep open gerneral purpose input/output pin name i/o description dc characteristics comment status o indicate working status if unused keep open netlight o indicate net status if unused keep open disp_data i/o disp _clk o disp _cs o disp _d/c o display interface if unused keep open scl o i 2 c bus clock vilmax=0.15 *vdd_ext vihmin=0.85*vdd_ext vilmin= 0v vihmax= vdd_ext vohmin= vdd_ext-0.1v volmax=0.1v vohmax= vdd_ext volmin= 0v if unused keep sim900_hd_v1.01 26.12.2009 18 free datasheet http://www..net/
sim900 hardware design sda i/o i 2 c bus data open kbr0~kbr4 o if unused keep these pins open kbc0~kbc4 i keypad interface pull up to vdd_ext, if unused keep pins open serial port pin name i/o description dc characteristics comment rxd i receive data txd o transmit data rts i request to send cts o clear to send ri o ring indicator dsr o data set ready dcd o data carry detect dtr i data terminal ready vilmax=0.15 *vdd_ext vihmin=0.85*vdd_ext vilmin= 0v vihmax= vdd_ext vohmin= vdd_ext-0.1v volmax=0.1v vohmax= vdd_ext volmin= 0v dtr pin has been pulled up to vdd_ext. if unused keep pin open debug interface pin name i/o description dc characteristics comment dbg_txd o dbg_rxd i serial interface for debugging and firmware upgrade vilmax=0.15 *vdd_ext vihmin=0.85*vdd_ext vilmin= 0v vihmax= vdd_ext vohmin= vdd_ext-0.1v volmax=0.1v vohmax= vdd_ext volmin= 0v if unused keep pins open sim interface pin name i/o description dc characteristics comment sim_vdd o voltage supply for sim card the voltage can be select by software automatically either 1.8v or 3v sim_data i/o sim data output sim_clk o sim clock sim_rst o sim reset vilmax=0.15 *sim_vdd vihmin=0.85*sim_vdd vilmin= 0v vihmax= sim_vdd vohmin= sim_vdd-0.1v volmax=0.1v vohmax= sim_vdd volmin= 0v all signals of sim interface are protected against esd with a tvs diode array. maximum cable length 200mm from the module pad to sim card sim900_hd_v1.01 26.12.2009 19 free datasheet http://www..net/
sim900 hardware design holder. sim_prese nce i sim detect vilmax=0.15 *vdd_ext vihmin=0.85*vdd_ext vilmin= 0v vihmax= vdd_ext if unused keep open adc pin name i/o description dc characteristics comment adc i general purpose analog to digital converter. input voltage range: 0v ~ 3v if unused keep open external reset pin name i/o description dc characteristics comment nreset i external reset input(active low) vilmax=0.15 *vdd_ext vihmin=0.85*vdd_ext vilmin= 0v vihmax= vdd_ext if unused keep open pulse width modulation pin name i/o description dc characteristics comment pwm1 o pwm output pwm2 o pwm output vohmin= vdd_ext-0.1v volmax=0.1v vohmax= vdd_ext volmin=0 if unused keep open 3.2 operating modes the table below briefly summarizes the various operating modes referred to in the following chapters. table 6 : overview of operating modes mode function gsm/gprs sleep module will automatically go into sleep mode if dt r is set to high level and there is no on air and no hardware interrupt (such as gpio interrupt or data on serial port). in this case, the current consumption of module will reduce to the minimal level. in sleep mode, the module can still receive paging message and sms from the system normally. normal operation gsm idle software is active. module has registered to the gsm network, and the module is ready to send and receive. sim900_hd_v1.01 26.12.2009 20 free datasheet http://www..net/
sim900 hardware design gsm talk connection between two subscribers is in progress. in this case, the power consumption depends on network settings such as dtx off/on, fr/efr/hr, hopping sequences, antenna. gprs standby module is ready for gprs data transfer, but no data is currently sent or received. in this case, power consum ption depends on network settings and gprs configuration. gprs data there is gprs data transfer (ppp or tcp or udp) in progress. in this case, power consumption is related with network settings (e.g. power control level), uplink / downlink data rates and gprs configuration (e.g. used multi-slot settings). power down normal shutdown by sending the ?at+cpowd=1? command or using the pwrkey. the power management asic disconnects the power supply from the baseband part of the module, and only the power supply for the rtc is remained. software is not active. the serial port is not accessible. operating volt age (connected to vbat) remains applied. minimum functionality mode (without remove power supply) use the ?at+cfun? command can set the module to a minimum functionality mode without remove the power supply. in this case, the rf part of the module will not work or the sim card will not be accessible, or both rf part and sim card will be closed, and the serial port is still accessible. the power consumption in this case is very low. 3.3 power supply the power supply of SIM900A is from a si ngle voltage source of vbat= 3.4v...4.5v. in some case, the ripple in a transmitting burst may cause voltage drops when current consumption rises to typical peaks of 2a. so the power supply must be able to provide sufficient current up to 2a. for the vbat input, a local bypass capacitor is recommended. a capacitor (about 100 f, low esr) is recommended. multi-layer ceramic chip (mlcc) capacito rs can provide the best combination of low esr and small size but may not be cost effective. a lower cost choi ce may be a 100 f tantalum capacitor (low esr) with a small (0.1f to 1f) ceramic in parallel, which is illustrated as following figure. the capacitors should be placed as close as possible to the SIM900A vbat pins. the following figure is the recommended circuit. c a c b vbat + figure 3: reference circu it of the vbat input sim900_hd_v1.01 26.12.2009 21 free datasheet http://www..net/
sim900 hardware design the circuit design of the power supply depends strongly upon the power source where this power is drained. the following figure is the reference design of +5v input source power supply. the designed output for the power supply is 4.1v, thus a linear regulator can be used. if there?s a big difference between the input source and the desired output (vbat), a switching converter power suppl y will be preferable because of its better efficiency especially with the 2a peak current in burst mode of the module. the single 3.6v li-ion cell battery type can be connected to the power supply of the SIM900A vbat directly. but the ni_cd or ni_mh battery types must be used carefully, since their maximum voltage can rise over the absolute maximum voltage for the module and damage it. figure 4: reference circuit of the source power supply input the following figure is the vbat voltage ripple wave at the maximum power transmit phase, the test condition is vbat=4.0v, vbat maximum output current =2a, c a =100f tantalum capacitor (esr=0.7 ? ) and c b =1f. max:300mv vbat burst:2a i vbat 4.615ms 577us figure 5: vbat voltage drop during transmit burst 3.3.1 power supply pins three vbat pins are dedicated to connect the supply voltage and fifteen gnd pins are dedicated to connect ground. vrtc pin can be used to back up the rtc. sim900_hd_v1.01 26.12.2009 22 free datasheet http://www..net/
sim900 hardware design 3.3.2 minimizing power losses when designing the power supply for your application please pay specific attention to power losses. ensure that the input voltage vbat never drops below 3.4v even in a transmit burst where current consumption can rise to typical peaks of 2a. if the power voltage drops below 3.4v, the module may be switched off. the pcb traces from the vbat pins to the power source must be wide enough to decrease voltage drops in the transmitting burst mode. 3.3.3 monitoring power supply to monitor the supply voltage, you can use the ?at+cbc? command which include a parameter: voltage value (in mv). the voltage is continuously measured at intervals depending on the operating mode. the displayed voltage (in mv) is averaged over the last measuring peri od before the at+cbc command is executed. for details plea se refer to document [1] 3.4 power up and power down scenarios in general, be sure not to turn on SIM900A while it is beyond the safety limits of voltage and temperature stated in chapter 3.4.2. SIM900A would immediately switch off after having started and detected these inappropriate conditions. in extreme cases this can cause permanent damage to the module. 3.4.1 turn on SIM900A SIM900A can be turned on by two ways, which are described in following chapters: z via pwrkey pin: starts normal operating mode (please refer to chapter 3.4.1.1) ; z via pwrkey pin and pwrkey_out pin starts normal operating mode note: the at command must be set after the SIM900A is power on and unsolicited result code ?rdy? is received from the serial port. however if the SIM900A is set autobauding, the serial port will receive nothing. the at commands can be set after the SIM900A is power on. you can use at+ipr=x to set a fixed baud rate and save the configuration to non-volatile flash memory . after the configuration is saved as fixed baud rate, the code ?rdy? should be received from the serial por t all the time that the SIM900A is power on. please refer to the chapter at+ipr in document [1]. 3.4.1.1 turn on SIM900A using the pwrkey pin (power on) you can turn on the SIM900A by driving the pwrkey to a low level voltage with a limiting current resistor (1k is recommended) in series for a short time and then release. this pin has pulled up to vdd_ext in the module. sim900_hd_v1.01 26.12.2009 23 free datasheet http://www..net/
sim900 hardware design the simple circuit illustrates as the following figures. 4.7k 47k turn on impulse pwrkey 1k figure 6: turn on SIM900A using driving circuit s1 pwrkey tvs1 1k figure 7 : turn on SIM900A using button the power on scenarios illustr ates as following figure. status output v il <0.15*vdd_ext v ih > 0.85*vdd_ext pulldown >1s vbat pwrkey (input) v oh > 0.85*vdd_ext delay > 2.2s serial port undefined active figure 8: timing of turn on system using pwrkey sim900_hd_v1.01 26.12.2009 24 free datasheet http://www..net/
sim900 hardware design when power on procedure completes, the SIM900A will send out following result code to indicate the module is ready to operate when set as fixed baud rate. rdy this result code does not appear when autobauding is active. 3.4.1.2 turn on SIM900A using the pwrkey pin and pwrkey_out pin (power on) user can turn on SIM900A by connecting pwrkey pin and pwrkey_out pin for a short time and then release. the simple circuit illustrates as the following figures. turn on/off impulse pwrkey_out pwrkey module sim900 100k figure 9: turn on SIM900A using driving circuit pwrkey_out pwrkey module sim900 figure 10: turn on SIM900A using button the power on scenarios illustr ates as following figure. sim900_hd_v1.01 26.12.2009 25 free datasheet http://www..net/
sim900 hardware design sim900_hd_v1.01 26.12.2009 26 status output impulse >1s vbat turn on impulse v oh > 0.85*vdd_ext delay > 2.2s serial port undefined active figure 11: timing of turn on system using pwrkey and pwrkey_out 3.4.2 turn off SIM900A following ways can be used to turn off the SIM900A: z normal power down procedure: turn off SIM900A using the pwrkey pin z normal power down procedure: turn off SIM900A using at command z over-voltage or under-voltage automatic shutdown: take effect if over-voltage or under-voltage is detected z over-temperature or under-temperature automatic shutdown: take effect if over-temperature or under-temperature is detected 3.4.2.1 turn off SIM900A using the pwrkey pin (power down) you can turn off the SIM900A by driving the pwrkey to a low level voltage for a short time and then release. you also can urn off the SIM900A by connecting pwrkey and pwrkey_out for a short time and then release. please refer to the turn on circuit. the power down scenar io illustrates as following figure. this procedure lets the module log off from the network and allows the software to enter into a secure state and save data before completely disconnecting the power supply. before the completion of the switching off procedure the module will send out result code: normal power down after this moment, the at commands can?t be executed. the module enters the power down mode, only the rtc is still active. power down can also be indicated by status pin, which is a low level voltage in this mode. free datasheet http://www..net/
sim900 hardware design sim900_hd_v1.01 26.12.2009 27 status output v il <0.15*vdd_ext v ih > 0.85*vdd_ext pulldown >1s pwrkey (input) v oh < 0.1v delay > 1.7s serial port undefined active logout net figure 12: timing of turn off system using pwrkey status output impulse >1s turn off impulse v oh < 0.1v delay > 1.7s serial port undefined active logout net figure 13: timing of turn off system using pwrkey and pwrkey_out 3.4.2.2 turn off SIM900A using at command you can use the at command ?at+cpowd=1? to turn off the module. this command lets the module log off from the network and allows the module to enter into a secure state and save data before completely disconnecting the power supply. before the completion of the switching off procedure the module will send out result code: normal power down after this moment, the at commands can?t be executed. the module enters the power down mode, only the rtc is still active. power down can also be indicated by status pin, which is a low level voltage in this mode. please refer to document [1] for detail about the at command of ?at+cpowd?. free datasheet http://www..net/
sim900 hardware design 3.4.2.3 over-voltage or unde r-voltage automatic shutdown the module will constantly monitor the voltage applied on the vbat. if the voltage 3.5v, the following urc will be presented: under-voltage warnning if the voltage 4.5v, the following urc will be presented: over-voltage warnning the uncritical voltage range is 3.4v to 4.6v. if the voltage > 4.6v or < 3.4v, the module will be automatic shutdown soon. if the voltage < 3.4v, the following urc will be presented: under-voltage power down if the voltage > 4.6v, the following urc will be presented: over-voltage power down after this moment, no further more at commands can be executed. the module logs off from network and enters power down mode, and only the rtc is still active. power down can also be indicated by status pin, which is a low level voltage in this mode. 3.4.2.4 over-temperature or unde r-temperature automatic shutdown the module will constantly monitor the temperature of the module, if the temperature > 80 , the following urc will be presented: +cmte:1 if the temperature < -30 , the following urc will be presented: +cmte:-1 the uncritical temperature range is -40 to 85 . if the temperature > 85 or < -40 , the module will be automatic shutdown soon. if the temperature > 85 , the following urc will be presented: +cmte:2 if the temperature < -40 , the following urc will be presented: +cmte:-2 after this moment, the at commands can?t be executed. the module logs off from network and enters power down mode, and only the rtc is still active. power down can also be indicated by status pin, which is a low level voltage in this mode. to monitor the temperature, you can use the ?at+cmte? command to read the temperature when the module is power on. for details plea se refer to document [1] 3.4.3 restart SIM900A using the pwrkey pin you can restart SIM900A by driving the pwrkey to a lo w level voltage for a short time and then release, the same as turning on SIM900A using the pwrkey pin. before restarting the SIM900A, you need delay at least 500ms from detecting the status low level on. the restarting scenario illustrates as the following figure. sim900_hd_v1.01 26.12.2009 28 free datasheet http://www..net/
sim900 hardware design turn off delay > 500ms restart pwrkey status figure 14: timing of restart system 3.5 power saving there are two methods for the module to enter into low current consumption status. ?at+cfun? is used to set module into minimum functionality mode and dtr hardware interface signal can be used to lead system to be in sleep mode (or slow clocking mode). 3.5.1 minimum functionality mode minimum functionality mode reduces the functionality of the module to a minimum and, thus, minimizes the current consumption to the lowest level. this mode is set with the ?at+cfun? command which provides the choice of the functionality levels =0 1 4 z 0: minimum functionality; z 1: full functionality (default); z 4: disable phone both transmit and receive rf circuits; if SIM900A has been set to minimum functionality by ?at+cfun=0?, the rf function and sim card function will be closed. in this case, the serial port is still accessible, but all at commands correlative with rf function or sim card function will not be accessible. if SIM900A has been set by ?at+cfun=4?, the rf function will be closed, the serial port is still active. in this case all at commands correlative with rf function will not be accessible. after SIM900A has been set by ?at+cfun=0? or ?at+cfun=4?, it can return to full functionality by ?at+cfun=1?. for detailed information about ?at+cfun?, please refer to document [1] . 3.5.2 sleep mode (slow clock mode) we can control SIM900A module to enter or exit the sleep mode in customer applications through dtr signal. when dtr is in high level and there is no on air and hardware interrupt (such as gpio interrupt or data on serial port), SIM900A will enter sleep mode automatically. in this mode, SIM900A can still receive paging or sms from network but the serial port is not accessible. note: for SIM900A, it requests to set at command ?at+csclk=1? to enable the sleep mode; the default value is 0, that can?t make the module enter sleep mode . for more details please re fer to our at command list. sim900_hd_v1.01 26.12.2009 29 free datasheet http://www..net/
sim900 hardware design 3.5.3 wake up SIM900A from sleep mode when SIM900A is in sleep mode, the following methods can wake up the module. z enable dtr pin to wake up SIM900A. if dtr pin is pulled down to a low level this signal will wake up SIM900A from power saving mode. the serial port will be active after dtr changed to low level for about 50ms. z receiving a voice or data call from network to wake up SIM900A. z receiving a sms from network to wake up SIM900A. 3.6 summary of state transitions (except sleep mode) the following figure shows how to proceed from one mode to another. normal mode normal mode power down mode power down mode at+cpowd or drive pwrkey to ground drive pwrkey to ground figure 15: state transition 3.7 rtc backup the rtc (real time clock) power supply of module can be provided by an external capacitor or a battery (rechargeable or non-charge able) through the vrtc. note: if the rtc function is enabled, a battery or capacitor should be connected with the vrtc pin. otherwise the vrtc pi n can be keep open. the following figures show various sample circuits for rtc backup. rtc core 10k SIM900A vrtc non-chargeable backup battery figure 16: rtc supply from non-chargeable battery sim900_hd_v1.01 26.12.2009 30 free datasheet http://www..net/
sim900 hardware design rtc core 10k SIM900A vrtc rechargeable backup battery figure 17: rtc supply fr om rechargeable battery rtc core 10k SIM900A vrtc large-capacitance capacitor figure 18: rtc suppl y from capacitor z li-battery backup coin-type rechargeable capacitor such as xh414h-iv01e form seiko can be used. typical charge curves for each cell type are shown in follo wing figures. note that th e rechargeable lithium type coin cells generally come pre-charged from the vendor. figure 19: seiko xh414h-iv01e charge characteristic sim900_hd_v1.01 26.12.2009 31 free datasheet http://www..net/
sim900 hardware design 3.8 serial interfaces table 7: pin definition of the serial interfaces name pin function dtr 3 data terminal ready ri 4 ring indicator dcd 5 data carrier detection dsr 6 date set ready cts 7 clear to send rts 8 request to send txd 9 transmit data serial port rxd 10 receive data dbg_rxd 28 receive data debug port dbg_txd 27 transmit data SIM900A provides two unbalanced asynchronous serial ports . one is the serial port and the other is the debug port. the gsm module is designed as a dce (data communication equipment), following the traditional dce-dte (data terminal equipment) connection. the module and the client (dte) are connected through the following signal (as following figure shows). autobauding supports baud rate from 1200bps to 115200bps. serial port z txd: send data to the rxd signal line of the dte z rxd: receive data from the txd signal line of the dte debug port z dbg_txd: send data to the rxd signal line of the dte z dbg_rxd: receive data from the txd signal line of the dte the logic levels are described in following table. table 8 : logic levels of the seri al port and debug port parameter min max unit v il 0 0.15*vdd_ext v v ih 0.85 *vdd_ext vdd_ext v v ol 0 0.1 v v oh vdd_ext -0.1 vdd_ext v sim900_hd_v1.01 26.12.2009 32 free datasheet http://www..net/
sim900 hardware design txd rxd rts cts dtr dcd ri txd rxd rts cts dtr dcd ring dbg_tx dbg_rx module (dce) customer (dte) serial port1 serial port debug port serial port2 txd rxd figure 20: connection of the serial interfaces 3.8.1 function of serial port & debug port supporting serial port z modem device. z contains data lines txd and rxd, state lines rt s and cts, control lines dtr, dcd, dsr and ri. z serial port can be used for csd fax, gprs service and send at command of controlling module. also serial port can be used for multiplexing function. SIM900A supports only basic mode of multiplexing so far. z serial port supports the communication rates as following: 1200,2400, 4800, 9600, 19200, 38400, 57600, 115200 default as 115200bps. z autobauding supports baud rates as following: 1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200bps. autobauding allows the gsm engine to automatically detect the baud rate configured in the host application. the serial port of the gsm engine supports autobauding for the following baud rates: 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200bps. factory setting is autobauding enabled. this gives you the flexibility to put the gsm engine into operation no matter what baud rate your host application is configured to. to take advantage of autobauding mode, specific attention should be paid to the following requirements: synchronization between dte and dce : when dce powers on with the autobauding enabled, it is recommended to wait 2 to 3 seconds before sending the first at character. you must first send ?a? to synchronize the band rate. after receiving the ?ok? response, dte and dce are correctly synchronized. the more in formation please refer to the at command ?at+ipr?. restrictions on au tobauding operation z the serial port has to be operated at 8 data bits, no parity and 1 stop bit (factory setting). sim900_hd_v1.01 26.12.2009 33 free datasheet http://www..net/
sim900 hardware design z the unsolicited result codes like "rdy", "+cfun: 1" and "+cpin: ready? are not indicated when you start up the me while autobauding is enabled. this is due to the fact that the new baud rate is not detected unless dte and dce are correctly synchronized as described above. note: you can use at+ipr=x to set a fixed baud rate an d save the configuration to non-volatile flash memory. after the configuration is saved as fixed baud rate , the unsolicited result codes like "rdy" should be received from the serial port all the time that the SIM900A is power on. debug port z null modem port z only contain data lines txd and rxd z debug port used for debugging and upgrading firmware. it cannot be used for csd call, fax call. and the debug port can not use multiplexing function. it does not support autobauding function. z debug port supports the communication rates is 115200bps 3.8.2 software upgrade and software debug the dbg_txd, dbg_rxd and gnd must be connected to the io connector when user need to upgrade software and debug software, the dbg_ txd, dbg_rxd should be used for software upgrade and for software debugging. the txd and rxd also should be connected to the io connector, if user wants to send at command or data stream to SIM900A. the pwrkey pin is recomm ended to connect to the io connector. the user also can add a switch between the pwrkey and the gnd. the pwrkey should be connected to the gnd when SIM900A is upgrading software. please refer to the following figure. module(dce) dbg_txd dbg_rxd gnd pwrkey txd rxd gnd 1k pwrkey serial port i/o connector figure 21: connection of softw are upgrade and software debug the serial port and the debug port don?t support the rs_232 level and it only supports the cmos level. please refer to the table 10 for details about the voltage level. you should add the level converter ic between the dce and dte, if you connect it to the computer. please refer to the following figure. sim900_hd_v1.01 26.12.2009 34 free datasheet http://www..net/
sim900 hardware design figure 22: rs232 level converter circuit 3.9 audio interfaces table 9 : pin define of the audio interface pin name pin number function mic_p 19 microphone1 input + mic_n 20 microphone1 input - spk_p 21 audio1 output+ ain/aout spk_n 22 audio1 output- linein_r 23 right channel input line in linein_l 24 lift channel input the module provides one analog input channel, ain, which may be used for microphone. the electret microphone is recommended when the interface is used for microphone. the outputs connect to the receiver. the receiver outputs only can directly drive 32 . external line inputs are available to directly mix or multiplex externally generated analog signals such as polyphonic tones from an external melody ic or music generated by an fm tuner ic or module. you can use at+cmic to adjust the input gain level of microphone, use at+sidet to set the side-tone level. in addition, you can also use at+clvl to adjust the output gain level. for more details, please refer to document [1] . it is suggested that you adopt one of the following two matching circuits in order to improve audio performance. the difference audio signals have to be layout according to difference signal layout rules. as show in following figures (note: all components package are 0603.) if you want to adopt an amp lifier circuit for audio, we recommend national company?s lm4890. of course you can select it according to your requirement. sim900_hd_v1.01 26.12.2009 35 free datasheet http://www..net/
sim900 hardware design 3.9.1 speaker interface configuration spk_p spk_n 10pf 10pf 10pf 33pf 33pf close to speaker gnd gnd differential layout 33pf esd anti esd anti module figure 23: speaker interface configuration spk_p spk_n differential layout amplifier circuit 10pf 10pf 33p f 33pf 33pf close to speaker gnd gnd 10pf esd anti esd anti module figure 24: speaker interface wi th amplifier configuration sim900_hd_v1.01 26.12.2009 36 free datasheet http://www..net/
sim900 hardware design 3.9.2 microphone interfaces configuration 10pf 33pf 33pf 33pf close to microphone mic_p mic_n gnd gnd difference layout electret microphone gnd gnd 10pf 10pf gnd gnd esd anti esd anti module figure 25: microphone interface configuration 3.9.3 earphone interface configuration 1 2 4 3 amphenol 9001-8905-050 spk_p mic_n mic_p 1uf 10r 68r 33pf gnd gnd gnd gnd close to module close to socket differnce layout 33pf 33pf 33pf 33pf 10pf gnd gnd gnd gnd module gnd gnd figure 26: earphone interfa ce configuration 3.9.4 referenced electronic characteristic sim900_hd_v1.01 26.12.2009 37 free datasheet http://www..net/
sim900 hardware design table 10 : mic input characteristics parameter min typ max unit working voltage 1.2 1.5 2.0 v working current 200 500 ua external microphone load resistance 1.2 2.2 k ohms table 11 : audio output characteristics parameter conditions min typ max unit rl=32 ohm thd=0.1% - 91 - mw normal output(spk) rl=32 ohm thd=1% - 96 - mw 3.10 sim card interface 3.10.1 sim card application you can use at command to get information in sim card. for more information, please refer to document [1] . the sim interface supports the functionality of the gsm phase 1 specificat ion and also supports the functionality of the new gsm phase 2+ specification for fast 64 kbps sim (intended for use with a sim application tool-kit). both 1.8v and 3.0v sim cards are supported. the sim interface is powered from an internal regulator in the module having normal voltage 3v. all pins reset as outputs driving low. logic levels are as described in table table 12 : pin define of the sim interface pin name pin number function sim_vdd 30 sim card power output automatic output on sim mode one is 3.0v10%, another is 1.8v10%. current is about 10ma. sim_data 31 sim card data i/o sim_clk 32 sim card clock sim_rst 33 sim card reset sim_presence 34 sim card detection following is the reference circuit about sim interface. we recommend an electro-static discharge device st ( www.st.com ) esda6v1w5 or on semi ( www.onsemi.com ) smf05c for ?esd anti?. the 22 ? resistors sim900_hd_v1.01 26.12.2009 38 free datasheet http://www..net/
sim900 hardware design showed in the following figure should be added in series on the io line between the module and the sim card for protecting the sim i/o port. the pull up resistor (about 15k ? ) on the sim_data line already added in the module. note that the sim peripheral circuit should be close to the sim card socket. the sim_presence pin is used for detecting the sim card insert or removal. you can use the at command ?at+csdt? to set the simcard configuration. for detail of this at command, please refer to document [1] : you can select the 8 pins sim card holder. the reference circuit about 8 pins sim card holder illustrates as following figure. module smf05c sim_vdd sim_clk sim_data sim_rst sim_presence vcc gnd rst vpp clk i/o presence gnd 10k 22r 22r 22r 220nf vdd_ext molex-91228 sim card 22pf figure 27: reference circuit of the 8 pins sim card if you don?t use the sim card detection function, you can leave the sim_presence pin open. the reference circuit about 6 pins sim card illustrates as following figure. module smf05c sim_vdd sim_clk sim_data sim_rst 22pf vcc gnd rst vpp clk i/o 22r 22r 22r 220nf c707 10m006 512 2 sim card figure 28: reference circuit of the 6 pins sim card sim900_hd_v1.01 26.12.2009 39 free datasheet http://www..net/
sim900 hardware design 3.10.2 design considerations for sim card holder for 6 pins sim card holder, we recommend to use amphenol c707 10m006 512 2 .you can visit http://www.amphenol.com for more information about the holder. figure 29: amphenol c707 10m006 512 2 sim card holder table 13 : pin description (amphe nol sim card holder) pin name signal description c1 sim_vdd sim card power supply, it can identify automatically the sim card power mode one is 3.0v10%, another is 1.8v10%. current is about 10ma. c2 sim_rst sim card reset. c3 sim_clk sim card clock. c5 gnd connect to gnd. c6 vpp not connect. c7 sim_data sim card data i/o. for 8 pins sim card holder, we recommend to use molex 91228.you can visit http://www.molex.com for more information about the holder. sim900_hd_v1.01 26.12.2009 40 free datasheet http://www..net/
sim900 hardware design sim900_hd_v1.01 26.12.2009 41 figure 30: molex 91228 sim card holder table 14 : pin description (mol ex sim card holder) pin name signal description c1 sim_vdd sim card power supply, it can identify automatically the sim card power mode one is 3.0v10%, another is 1.8v10%. current is about 10ma. c2 sim_rst sim card reset c3 sim_clk sim card clock c4 gnd connect to gnd c5 gnd connect to gnd c6 vpp not connect c7 sim_data sim card data i/o c8 sim_presence detect sim card presence free datasheet http://www..net/
sim900 hardware design 3.11 lcd display interface SIM900A provides a serial lcd display interface that supports serial communication with lcd device. when used as lcd interface, the following table is th e pin definition. lcd interface timing should be united with the lcd device. table 15 : pin define of the lcd interface pin name pin number function disp_clk 11 display clock for lcd disp_data 12 display data output disp_d/c 13 display data or command select disp_cs 14 display enable note: this function is not supported in the default firmware. there must be some customized firmware if you want. please contact si mcom for more details. 3.12 keypad interface the keypad interface consists of 5 keypad column outputs and 5 keypad row inputs. the basic configuration is 5 keypad columns and 5 keypad rows, giving 25 keys. table 16 : pin define of the keypad interface pin name pin number default function second function* default state gpio1/ kbr4 40 gpio1 output pull down gpio2/ kbr3 41 gpio2 output pull down gpio3/ kbr2 42 gpio3 output pull down gpio4/ kbr1 43 gpio4 output pull down gpio5/ kbr0 44 gpio5 keypad matrix column output pull down gpio6/ kbc4 47 gpio6 output pull down gpio7/ kbc3 48 gpio7 output pull down gpio8/ kbc2 49 gpio8 output pull down gpio9/ kbc1 50 gpio9 output pull down gpio10/ kbc0 51 gpio10 keypad matrix row output pull down the keypad interface allows a direct external matrix co nnection. a typical recommended circuit about the keypad is as shown in the following figure. sim900_hd_v1.01 26.12.2009 42 free datasheet http://www..net/
sim900 hardware design kbr4 kbr3 kbr2 kbr1 kbr0 kbc0 kbc1 kbc2 kbc3 kbc4 gnd module figure 31: reference circuit of the keypad interface * note: this function is not supported in the default firmwa re. there must be customized firmware if you want. please contact simcom for more details. 3.13 adc SIM900A provides one auxiliary adc (general purpose analog to digital converter.) as voltage input pin, which can be used to detect the values of some external items such as voltage, temperature etc. we can use at command ?at+cadc? to read the voltage value on adc. for detail of this at command, please refer to document [1] . 10k 2.8v adc aux adc module figure 32: architecture of adc sim900_hd_v1.01 26.12.2009 43 free datasheet http://www..net/
sim900 hardware design table 17 : adc specification min type max units voltage range 0 - 2.8 v adc resolution - 10 - bits sampling rate - - 200k hz 3.14 behaviors of the ri table 18 : behaviours of the ri state ri respond standby high voice calling change low, then: 1 change to high when establish calling. 2 use at command ath, the ri pin changes to high. 3 sender hangs up, change to high. data calling change low, then 1 change to high when establish calling. 2 use at command ath, the ri changes to high. sms when receive sms, the ri will change to low and hold low level about 120 ms, then change to high. urc some urcs triggers 120ms low level on ri. for more details, please refer to document [10] if the module is used as caller, the ri will maintain high. however, when it is used as receiver, following is timing of ring. power on ring mo or mt hang up ring hang on (talking) mo or mt hang up ring ri high low figure 33: SIM900A services as receiver sim900_hd_v1.01 26.12.2009 44 free datasheet http://www..net/
sim900 hardware design ri power on calling hang up echo talking calling echo hang up high lo w figure 34: SIM900A services as caller 3.15 network status indication the netlight can be used to drive a network status in dication led lamp. the worki ng state of this pin is listed in following table: table 19 : working state of the netlight state SIM900A function off SIM900A is not running 64ms on/ 800ms off SIM900A does not find the network 64ms on/ 3000ms off SIM900A find the network 64ms on/ 300ms off gprs communication we provide a reference circuit for you, shown as following figure: sim900_hd_v1.01 26.12.2009 45 free datasheet http://www..net/
sim900 hardware design 300r 4.7k 47k vbat module netlight figure 35: reference circuit of netlight 3.16 general purpose input output (gpio) SIM900A provides a limited number of general purpose input/output signal pin. the output and input voltage level of the gpio can be set by at command. for more details, please refer to document [1] table 20 : pin define of the gpio interface pin name pin number default function second function* default state gpio1/ kbr4 40 gpio1 kbr4 output pull down gpio2/ kbr3 41 gpio2 kbr3 output pull down gpio3/ kbr2 42 gpio3 kbr2 output pull down gpio4/ kbr1 43 gpio4 kbr1 output pull down gpio5/ kbr0 44 gpio5 kbr0 output pull down gpio6/ kbc4 47 gpio6 kbc4 output pull down gpio7/ kbc3 48 gpio7 kbc3 output pull down gpio8/ kbc2 49 gpio8 kbc2 output pull down gpio9/ kbc1 50 gpio9 kbc1 output pull down gpio10/ kbc0 51 gpio10 kbc0 output pull down gpio11 67 gpio11 output pull down gpio12 68 gpio12 output pull down * note: this function is not supported in the default firmwa re. there must be customized firmware if you want. please contact simcom for more details. sim900_hd_v1.01 26.12.2009 46 free datasheet http://www..net/
sim900 hardware design 3.17 external reset the external nreset pin provides a means for external ci rcuitry to force the device into a reset state. this signal has to be considered as an emergency reset only. asserting an active-low signal on the nreset pin generates a reset; already pull up in module. a decoupling of the nreset pin may be necessary to avoid erroneous noise-induced resets. status output v il <0.15*vdd_ext v ih > 0.85*vdd_ext vbat nreset v oh > 0.85*vdd_ext min:20us typ:50us min:1.2s v ol < 0.1v figure 36: reset timing 3.18 pwm SIM900A contains two dc pulse-width modulators (pwms) which can be used in conjunction with an external transistor for driving a vibrator, or a backlight led for illuminating an lcd display or keyboard. each pwm features 7-bit resolution and a maximum conversion rate is 3.25 mhz. each pwm uses two 7-bit unsigned binary numbers: one for the output period and one for the pulse width or the duty cycle. table 21: pin define of the pwm pin name pin number pwm1 35 pulse-width modulator signal pwm2 36 pulse-width modulator signal note: this function is not supported in the default firmwa re. there must be customized firmware if you want. please contact simcom for more details. 3.19 i2c bus the SIM900A initiates a data transfer on the bus and ge nerates the clock signal to execute the transfer. the features include the following: z maximum output rate equal to 400 kbit/s z open-drain outputs z automatic start and stop generation z automatic acknowledge generation and checking sim900_hd_v1.01 26.12.2009 47 free datasheet http://www..net/
sim900 hardware design 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 firmwa re. there must be customized firmware if you want. please contact simcom for more details. 4 antenna interface SIM900A provides rf antenna interface. and customer?s an tenna should be located in the customer?s main board and connect to module?s antenna pad through microstrip li ne or other type rf trace which impendence must be controlled in 50 ? . to help you to ground the antenna, SIM900A comes with a grounding plane located close to the antenna pad. the pin 60 is the rf antenna pad. SIM900A material properties: SIM900A pcb material: fr4 antenna pad: gold plated pad 4.2 module rf output power table 23 : SIM900A conducted rf output power frequency max min egsm900 33dbm 2db 5dbm5db dcs1800 30dbm 2db 0dbm5db 4.3 module rf receive sensitivity table 24 : SIM900A conducted rf receive sensitivity frequency receive sensitivity egsm900 < -106dbm dcs1800 < -106dbm pin name pin number function scl 38 i2c bus clock sda 37 i2c bus data sim900_hd_v1.01 26.12.2009 48 free datasheet http://www..net/
sim900 hardware design 4.4 module operating frequencies table 25 : SIM900A operating frequencies frequency receive transmit egsm900 925 960mhz 880 915mhz dcs1800 1805 1880mhz 1710 1785mhz 5 electrical, reliability and radio characteristics 5.1 absolute maximum ratings the absolute maximum ratings stated in table 28 are stress ratings under non-operating conditions. stresses beyond any of these limits will cause permanent damage to SIM900A. table 26 : absolute maximum ratings parameter min max unit vbat - 5.5 v peak current of power supply 0 3.0 a voltage at digit pins* -0.3 3.1 v i i * - 10 ma i o * - 10 ma *for digital interface pins, such as ke ypad, gpio, i2c, uart, lcd and pwms. 5.2 operating temperatures the operating temperature is listed in following table: table 27 : SIM900A operating temperature parameter min typ max unit ambient temperature -30 25 80 restricted operation* -40 to -30 80 to 85 storage temperature -45 90 * the SIM900A does work, but deviations from the gsm specification may occur. sim900_hd_v1.01 26.12.2009 49 free datasheet http://www..net/
sim900 hardware design 5.3 power supply ratings table 28 : SIM900A power supply ratings parameter description conditions min typ max unit supply voltage voltage must stay within the min/max values, including voltage drop, ripple, and spikes. 3.4 4.0 4.5 v voltage drop during transmit burst normal condition, power control level for pout max 400 mv vbat voltage ripple normal condition, power control level for pout max @ f<200khz @ f>200khz 50 2 mv p ower down mode sleep mode 30 1.5 ua ma idle mode egsm 900 dcs1800 22 22 ma talk mode egsm 900 dcs1800 241 158 ma data mode, gprs (3 rx,2tx) egsm 900 dcs1800 444 287 ma i vbat average supply current data mode, gprs (4 rx,1tx) egsm 900 dcs1800 270 191 ma peak supply current (during tx burst) power control leve l for pout max. 2.0 a 5.4 current consumption please refer to the following table for the values of current consumption. table 29 : SIM900A current consumption sim900_hd_v1.01 26.12.2009 50 free datasheet http://www..net/
sim900 hardware design voice call egsm 900 @power level #5 <300ma,typical 250ma @power level #10,typical 110ma @power level #19,typical 76ma dcs 1800 @power level #0 <200ma,typical 168ma @power level #10,typical 89ma @power level #15,typical 76ma gprs data data mode, gprs ( 1 rx,1 tx ) class 8 egsm 900 @power level #5 <300ma,typical 240ma @power level #10,typical 110ma @power level #19,typical 83ma dcs 1800 @power level #0 <200ma,typical 170ma @power level #10,typical 95ma @power level #15,typical 80ma data mode, gprs ( 3 rx, 2 tx ) class 10 egsm 900 @power level #5 <450ma,typical 440ma @power level #10,typical 185ma @power level #19,typical 130ma dcs 1800 @power level #0 <350ma,typical 300ma @power level #10,typical 155ma @power level #15,typical 122ma data mode, gprs ( 4 rx,1 tx ) class 8 egsm 900 @power level #5 <300ma,typical 270ma @power level #10,typical 150ma @power level #19,typical 120ma dcs 1800 @power level #0 <300ma,typical 205ma @power level #10,typical 130ma @power level #15,typical 115ma class 10 is default set when the module works at data translation mode, the module can also work at class 8 set by at command. 5.5 electro-static discharge the gsm engine is not protected against electrostatic discha rge (esd) in general. therefore, it is subject to esd handing precautions that typically apply to esd sensitive components. proper esd handing and packaging procedures must be applied throughout the processing, handing and operation of any application using a SIM900A module. the measured values of SIM900A are shown as the following table: table 30 : the esd endure statue measured tabl e (temperature: 25 , humidity:45% ) sim900_hd_v1.01 26.12.2009 51 free datasheet http://www..net/
sim900 hardware design part contact discharge air discharge vbat 5kv 10kv gnd 4kv 10kv rxd, txd 3kv 6kv antenna port 5kv 10kv spk_p/n mic_p/n 2kv 6kv pwrkey 1kv 6kv other port tbd tbd 6 mechanics this chapter describes the mechanical dimensions of SIM900A. 6.1 mechanical dimensions of SIM900A following shows the mechanical dimensions of SIM900A (top view, side view and bottom view). figure 37: top an side mech anical dimensions of module unit: mm sim900_hd_v1.01 26.12.2009 52 free datasheet http://www..net/
sim900 hardware design figure 38 bottom mechanical di mensions of module unit: mm figure 39: recommended pcb decal unit: mm sim900_hd_v1.01 26.12.2009 53 free datasheet http://www..net/
sim900 hardware design note: area a is keep route out area. area b should be covered by silkscreen to prevent from the short between the via on customer boar d and the test points on the bottom side of the module. 6.2 top and bottom view of the SIM900A figure 40: top view of the SIM900A sim900_hd_v1.01 26.12.2009 54 free datasheet http://www..net/
sim900 hardware design 6.3 pin assignment of SIM900A SIM900A top view 1 2 17 3 4 10 5 11 6 12 13 7 14 8 15 16 9 52 53 68 54 55 61 56 62 57 63 64 58 65 59 66 67 60 51 50 35 49 48 42 47 41 46 40 39 45 38 44 37 36 43 34 33 18 32 31 25 30 24 29 23 22 28 21 27 20 19 26 pwrkey_out pwrkey dtr ri dcd dsr cts rts txd rxd disp_clk disp_data disp_d/c disp_cs vdd_ext nreset gnd gnd mic_p mic_n spk_p spk_n linein_r linein_l adc vrtc dbg_txd dbg_rxd gnd sim_vdd sim_data sim_clk sim_rst sim_presence pwm1 pwm2 sda scl gnd gpio1/kbr4 gpio2/kbr3 gpio3/kbr2 gpio4/kbr1 gpio5/kbr0 gpio6/kbc4 gpio7/kbc3 gpio8/kbc2 gpio9/kbc1 gpio10/kbc0 gnd gnd netlight gnd gnd vbat vbat vbat gnd gnd rf_ant gnd gnd gnd gnd gnd status gpio11 gpio12 figure 41: SIM900A pin out diagram (top view) table 31 : pin assignment pin number pin name pin number pin name 1 pwrkey 35 pmw1 2 pwrkey_out 36 pwm2 3 dtr 37 sda 4 ri 38 scl 5 dcd 39 gnd 6 dsr 40 gpio1/kbr4 7 cts 41 gpio2/kbr3 8 rts 42 gpio3/kbr2 9 txd 43 gpio4/kbr1 sim900_hd_v1.01 26.12.2009 55 free datasheet http://www..net/
sim900 hardware design 10 rxd 44 gpio5/kbr0 11 disp_clk 45 gnd 12 disp_data 46 gnd 13 disp_d/c 47 gpio6/kbc4 14 disp_cs 48 gpio7/kbc3 15 vdd_ext 49 gpio8/kbc2 16 nreset 50 gpio9/kbc1 17 gnd 51 gpio10/kbc0 18 gnd 52 netlight 19 mic_p 53 gnd 20 mic_n 54 gnd 21 spk_p 55 vbat 22 spk_n 56 vbat 23 linein_r 57 vbat 24 linein_l 58 gnd 25 adc 59 gnd 26 vrtc 60 rf_ant 27 dbg_txd 61 gnd 28 dbg_rxd 62 gnd 29 gnd 63 gnd 30 sim_vdd 64 gnd 31 sim_data 65 gnd 32 sim_clk 66 status 33 sim_rst 67 gpio11 34 sim_presence 68 gpio12 sim900_hd_v1.01 26.12.2009 56 free datasheet http://www..net/
sim900 hardware design 6.4 the ramp-soak-spike reflow profile of SIM900A figure 42: the ramp-soak-spike reflow profile of SIM900A sim900_hd_v1.01 26.12.2009 57 free datasheet http://www..net/
sim900 hardware design contact us: shanghai simcom wireless solutions ltd. add: sim technology building no.633 jinzhong road changning district shanghai p.r. china 200335 tel: +86 21 3235 3300 fax: +86 21 3235 3301 url: www.sim.com/wm sim900_hd_v1.01 26.12.2009 58 free datasheet http://www..net/

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