SIM868_Hardware_Design_V1.01 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                                                                                                                            Smart Machine Smart Decision 
 
 
Document Title 
SIM868 Hardware Design 
Version 
Date 
Status 
V1.01 
2016-08-01 
Release 
Document Control ID 
SIM868_Hardware_Design_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  information  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 customer’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  the  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. 2016 
SIM868_Hardware_Design_V1.01                                            2                                                                            2016-08-01 
                                                                                                                                            Smart Machine Smart Decision 
Contents 
1. 
Introduction .......................................................................................................... 8 
2.  SIM868 Overview ................................................................................................ 8 
SIM868 ................................................................................................................................. 9 
2.1. 
SIM868 Key Features ........................................................................................................... 9 
2.2. 
2.3.  Operating Mode .................................................................................................................. 11 
2.4. 
Functional Diagram............................................................................................................. 12 
3.  Package Information ......................................................................................... 14 
3.1. 
3.2. 
3.3. 
Pin Out Diagram ................................................................................................................. 14 
Pin Description .................................................................................................................... 14 
Package Dimensions ........................................................................................................... 17 
4.  Application Interface ......................................................................................... 20 
4.1. 
4.2. 
4.3. 
4.4. 
4.5. 
Power Supply ...................................................................................................................... 20 
4.1.1.  Power Supply Pin ................................................................................................................................ 21 
4.1.2.  Monitoring Power Supply ................................................................................................................... 22 
Power on/off SIM868.......................................................................................................... 22 
4.2.1.  Power on SIM868 ............................................................................................................................... 22 
4.2.2.  Power off SIM868 ............................................................................................................................... 23 
Power Saving Mode ............................................................................................................ 24 
4.3.1.  Minimum Functionality Mode ............................................................................................................ 24 
4.3.2.  Sleep Mode 1 (AT+CSCLK=1) .......................................................................................................... 25 
4.3.3.  Wake Up SIM868 from Sleep Mode 1 ................................................................................................ 25 
4.3.4.  Sleep Mode 2 (AT+CSCLK=2) .......................................................................................................... 25 
4.3.5.  Wake Up SIM868 from Sleep Mode 2 ................................................................................................ 25 
Power Saving Mode ............................................................................................................ 26 
Serial Port and USB Interface ............................................................................................. 26 
4.5.1 
Function of Serial Port ........................................................................................................................ 27 
4.5.2 
Serial Interfaces ................................................................................................................................... 28 
4.5.3  Debug Interface ................................................................................................................................... 29 
4.5.4 
Software Upgrade ................................................................................................................................ 30 
4.6.  UART1_RI Behaviors ......................................................................................................... 31 
4.7.  Audio Interfaces .................................................................................................................. 32 
4.7.1.  Speaker Interfaces Configuration ........................................................................................................ 33 
4.7.2.  Microphone Interfaces Configuration ................................................................................................. 33 
4.7.3.  Audio Electronic Characteristic .......................................................................................................... 33 
4.7.4.  TDD .................................................................................................................................................... 34 
SIM Card Interface.............................................................................................................. 34 
4.8.1.  SIM Card Application ......................................................................................................................... 34 
4.8.2.  SIM Card Design Guide ...................................................................................................................... 36 
4.8.3.  Design Considerations for SIM Card Holder ...................................................................................... 36 
SD Interface ........................................................................................................................ 38 
4.8. 
4.9. 
SIM868_Hardware_Design_V1.01                                            3                                                                            2016-08-01 
                                                                                                                                            Smart Machine Smart Decision 
4.10. 
I2C Bus ............................................................................................................................... 38 
4.11.  ADC .................................................................................................................................... 38 
4.12.  Network Status Indication ................................................................................................... 39 
4.13.  Operating Status Indication ................................................................................................. 40 
4.14.  RF Synchronization Signal ................................................................................................. 40 
4.15.  GNSS .................................................................................................................................. 40 
4.15.1.  GNSS Overview .............................................................................................................................. 40 
Power on/down GNSS ..................................................................................................................... 41 
4.15.2. 
4.15.3. 
1PPS Output..................................................................................................................................... 41 
4.16.  Antenna Interface ................................................................................................................ 41 
4.16.1.  GSM Antenna Interface ................................................................................................................... 41 
4.16.2.  GNSS Antenna Interface .................................................................................................................. 42 
5.  PCB Layout ........................................................................................................ 44 
5.1 
5.2 
Pin Assignment ................................................................................................................... 44 
Principle of PCB Layout ..................................................................................................... 45 
5.2.1  Antenna Interface ................................................................................................................................ 45 
5.2.2 
Power Supply ...................................................................................................................................... 45 
5.2.3 
SIM Card Interface .............................................................................................................................. 45 
5.2.4  Audio Interface.................................................................................................................................... 45 
5.2.5  Others .................................................................................................................................................. 45 
6.  Electrical, Reliability and Radio Characteristics ........................................... 46 
6.1 
6.2 
6.3 
6.4 
6.5 
6.6 
6.7 
6.8 
6.9 
Absolute Maximum Ratings ............................................................................................... 46 
Recommended Operating Conditions ................................................................................. 46 
Digital Interface Characteristics .......................................................................................... 46 
SIM Card Interface Characteristics ..................................................................................... 47 
SIM_VDD Characteristics .................................................................................................. 47 
VDD_EXT Characteristics ................................................................................................. 47 
Current Consumption(VBAT=4.0V) ............................................................................. 47 
Electro-Static Discharge ..................................................................................................... 48 
Radio Characteristics .......................................................................................................... 49 
6.9.1  Module RF Output Power ................................................................................................................... 49 
6.9.2  Module RF Receive Sensitivity ........................................................................................................... 50 
6.9.3  Module Operating Frequencies ........................................................................................................... 50 
7.  Manufacturing ................................................................................................... 51 
7.1. 
Top and Bottom View of SIM868 ...................................................................................... 51 
7.2. 
Typical Solder Reflow Profile ............................................................................................ 51 
7.3. 
The Moisture Sensitivity Level ........................................................................................... 52 
7.4.  Baking Requirements .......................................................................................................... 52 
8.  Appendix ............................................................................................................. 53 
I. 
II. 
III. 
Related Documents ............................................................................................................. 53 
Terms and Abbreviations .................................................................................................... 54 
Safety Caution ..................................................................................................................... 56 
SIM868_Hardware_Design_V1.01                                            4                                                                            2016-08-01 
                                                                                                                                            Smart Machine Smart Decision 
 
Table Index 
TABLE 1: MODULE INFORMATION ............................................................................................................................. 9 
TABLE 2: SIM868 KEY FEATURES ................................................................................................................................ 9 
TABLE 3: GNSS ENGINE PERFORMANCE ................................................................................................................ 10 
TABLE 4: CODING SCHEMES AND MAXIMUM NET DATA RATES OVER AIR INTERFACE ............................ 11 
TABLE 5: OVERVIEW OF OPERATING MODES ........................................................................................................ 11 
TABLE 6: PIN DESCRIPTION ....................................................................................................................................... 14 
TABLE 7: RECOMMENDED ZENER DIODE .............................................................................................................. 20 
TABLE 8: THE CURRENT CONSUMPTION OF FUNCTION MODE ........................................................................ 24 
TABLE 9: SERIAL PORT AND USB PIN DEFINITION ............................................................................................... 27 
TABLE 10: SERIAL PORT CHARACTERISTICS ......................................................................................................... 27 
TABLE 11: USB_VBUS OPERATION VOLTAGE ........................................................................................................ 30 
TABLE 12: RI BEHAVIORS ........................................................................................................................................... 31 
TABLE 13: AUDIO INTERFACE DEFINITION ............................................................................................................ 32 
TABLE 14: PERFORMANCE OF AUDIO AMPLIFIER ................................................................................................ 32 
TABLE 15: MICROPHONE INPUT CHARACTERISTICS........................................................................................... 33 
TABLE 16: AUDIO OUTPUT CHARACTERISTICS .................................................................................................... 34 
TABLE 17: SIM PIN DEFINITION ................................................................................................................................. 34 
TABLE 18: PIN DESCRIPTION (MOLEX SIM CARD HOLDER) .............................................................................. 36 
TABLE 19: PIN DESCRIPTION (AMPHENOL SIM CARD HOLDER) ....................................................................... 37 
TABLE 20: PIN DEFINITION OF THE I2C ................................................................................................................... 38 
TABLE 21: PIN DEFINITION OF THE ADC ................................................................................................................. 38 
TABLE 22: ADC SPECIFICATION ................................................................................................................................ 39 
TABLE 23: PIN DEFINITION OF THE NETLIGHT ..................................................................................................... 39 
TABLE 24: STATUS OF THE NETLIGHT PIN .............................................................................................................. 39 
TABLE 25: PIN DEFINITION OF THE STATUS ........................................................................................................... 40 
TABLE 26: DEFINITION OF THE RF_SYNC PIN........................................................................................................ 40 
TABLE 27: RECOMMENDED TVS COMPONENT ..................................................................................................... 42 
TABLE 28: ABSOLUTE MAXIMUM RATINGS........................................................................................................... 46 
TABLE 29: DIGITAL INTERFACE CHARACTERISTICS ........................................................................................... 46 
TABLE 30: SIM CARD INTERFACE CHARACTERISTICS ........................................................................................ 47 
TABLE 31: SIM_VDD CHARACTERISTICS ................................................................................................................ 47 
TABLE 32: VDD_EXT CHARACTERISTICS ............................................................................................................... 47 
TABLE 33: CURRENT CONSUMPTION ...................................................................................................................... 47 
TABLE 34: THE ESD CHARACTERISTICS (TEMPERATURE: 25℃, HUMIDITY: 45 %) ....................................... 48 
TABLE 35: GSM850 AND EGSM900 CONDUCTED RF OUTPUT POWER .............................................................. 49 
TABLE 36: DCS1800 AND PCS1900 CONDUCTED RF OUTPUT POWER ............................................................... 49 
TABLE 37: CONDUCTED RF RECEIVE SENSITIVITY ............................................................................................. 50 
TABLE 38: MOISTURE SENSITIVITY LEVEL AND FLOOR LIFE ........................................................................... 52 
TABLE 39: BAKING REQUIREMENTS ....................................................................................................................... 52 
TABLE 40: RELATED DOCUMENTS ........................................................................................................................... 53 
TABLE 41: TERMS AND ABBREVIATIONS ................................................................................................................ 54 
TABLE 42: SAFETY CAUTION ..................................................................................................................................... 56 
SIM868_Hardware_Design_V1.01                                            5                                                                            2016-08-01 
                                                                                                                                            Smart Machine Smart Decision 
Figure Index 
FIGURE 1: SIM868 FUNCTIONAL DIAGRAM ........................................................................................................... 13 
FIGURE 2: PIN OUT DIAGRAM (TOP VIEW) ............................................................................................................. 14 
FIGURE 3: DIMENSIONS OF SIM868 (UNIT: MM) .................................................................................................... 17 
FIGURE 4: RECOMMENDED PCB FOOTPRINT OUTLINE (UNIT: MM) ................................................................ 18 
FIGURE 5: RECOMMENDED SMT STENCIL FOOTPRINT OUTLINE (UNIT: MM) .............................................. 19 
FIGURE 6: REFERENCE CIRCUIT OF THE VBAT INPUT ......................................................................................... 20 
FIGURE 7: REFERENCE CIRCUIT OF THE LDO POWER SUPPLY ......................................................................... 20 
FIGURE 8: REFERENCE CIRCUIT OF THE DC-DC POWER SUPPLY ..................................................................... 21 
FIGURE 9: VBAT VOLTAGE DROP DURING TRANSMIT BURST ........................................................................... 21 
FIGURE 10: THE MINIMAL VBAT VOLTAGE REQUIREMENT AT VBAT DROP .................................................. 21 
FIGURE 11: POWERED ON/DOWN MODULE USING TRANSISTOR ..................................................................... 22 
FIGURE 12: POWERED ON/DOWN MODULE USING BUTTON ............................................................................. 22 
FIGURE 13: TIMING OF POWER ON MODULE ......................................................................................................... 22 
FIGURE 14: TIMING OF POWER OFF SIM868 BY PWRKEY ................................................................................... 23 
FIGURE 15: TIMING OF RESTART SIM868 ................................................................................................................ 24 
FIGURE 16: RTC SUPPLY FROM CAPACITOR ........................................................................................................... 26 
FIGURE 17: RTC SUPPLY FROM NON-CHARGEABLE BATTERY ......................................................................... 26 
FIGURE 18: RTC SUPPLY FROM RECHARGEABLE BATTERY .............................................................................. 26 
FIGURE 19: CONNECTION OF THE SERIAL INTERFACES ..................................................................................... 28 
FIGURE 20: RESISTOR MATCHING CIRCUIT ........................................................................................................... 28 
FIGURE 21 : DIODE ISOLATION CIRCUIT ................................................................................................................. 29 
FIGURE 22: TX LEVEL MATCHING CIRCUIT ........................................................................................................... 29 
FIGURE 23: RX LEVEL MATCHING CIRCUIT ........................................................................................................... 29 
FIGURE 24: USB REFERENCE CIRCUIT .................................................................................................................... 30 
FIGURE 25: CONNECTION FOR SOFTWARE UPGRADING AND DEBUGGING .................................................. 30 
FIGURE 26: CONNECTION FOR SOFTWARE UPGRADING AND DEBUGGING .................................................. 31 
FIGURE 27: UART1_RI BEHAVIOUR OF VOICE CALLING AS A RECEIVER ....................................................... 31 
FIGURE 28: UART1_RI BEHAVIOUR OF URC OR RECEIVE SMS .......................................................................... 32 
FIGURE 29: UART1_RI BEHAVIOUR AS A CALLER ................................................................................................. 32 
FIGURE 30: SPEAKER REFERENCE CIRCUIT .......................................................................................................... 33 
FIGURE 31: MICROPHONE REFERENCE CIRCUIT .................................................................................................. 33 
FIGURE 32: REFERENCE CIRCUIT OF THE 8-PIN SIM CARD HOLDER ............................................................... 35 
FIGURE 33: REFERENCE CIRCUIT OF THE 6-PIN SIM CARD HOLDER ............................................................... 35 
FIGURE 34: MOLEX 91228 SIM CARD HOLDER ...................................................................................................... 36 
FIGURE 35: AMPHENOL C707 10M006 512 SIM CARD HOLDER ........................................................................... 37 
FIGURE 36: SD REFERENCE CIRCUIT ....................................................................................................................... 38 
FIGURE 37: REFERENCE CIRCUIT OF NETLIGHT .................................................................................................. 39 
FIGURE 38: RF_SYNC SIGNAL DURING TRANSMIT BURST ................................................................................ 40 
FIGURE 39: GSM ANTENNA MATCHING CIRCUIT ................................................................................................. 41 
FIGURE 40: GSM ANTENNA MATCHING CIRCUIT WITHOUT RF CONNECTOR ............................................... 42 
FIGURE 41: GNSS PASSIVE ANTENNA MATCHING CIRCUIT ............................................................................... 43 
FIGURE 42: GNSS ACTIVE ANTENNA MATCHING CIRCUIT ................................................................................. 43 
FIGURE 43: PIN ASSIGNMENT .................................................................................................................................... 44 
FIGURE 44: TOP AND BOTTOM VIEW OF SIM868 ................................................................................................... 51 
FIGURE 45: TYPICAL SOLDER REFLOW PROFILE OF LEAD-FREE PROCESS .................................................. 51 
 
SIM868_Hardware_Design_V1.01                                            6                                                                            2016-08-01 
                                                                                                                                            Smart Machine Smart Decision 
Version History 
Date 
Version 
Description of change 
2016-06-20 
1.00 
Origin 
1.  Update figure 1 
2.  Add voltage range of GPS_VBAT 
3.  Add voltage range of VRTC 
4.  Add voltage range of GNSS_EN 
5.  Add Recommenced SMT stencil footprint 
2016-08-01 
1.01 
6.  Delete Over-Temperature or Under- Temperature Power off 
7.  Change  PWRKEY  pin  from  at  least  1  second  to  1.5  second  for 
power off the module 
8.  Add GNSS software update part 
9.  Delete Multiplexing function 
10.  Add BPF component in GNSS part 
Author 
Yanwu.Wang; 
Xiaoxu.Chen 
Yanwu.Wang; 
Xiaoxu.Chen 
SIM868_Hardware_Design_V1.01                                            7                                                                            2016-08-01 
                                                                                                                                            Smart Machine Smart Decision 
1.  Introduction   
This document describes SIM868 hardware interface in great detail. The document can help customer to quickly 
understand  SIM868  interface  specifications,  electrical  and  mechanical  details.  With  the  help  of  this  document 
and other SIM868 application notes, customer guide, customers can use SIM868 to design various applications 
quickly. 
 
2.  SIM868 Overview 
Designed  for  global  market,  SIM868  is  integrated  with  a  high  performance  GSM/GPRS  engine  and  a  GNSS 
engine. SIM868 is a quad-band GSM/GPRS module that works on frequencies GSM 850MHz, EGSM 900MHz, 
DCS 1800MHz and PCS 1900MHz. SIM868 features GPRS multi-slot class 12/class 10 (optional) and supports 
the GPRS coding schemes CS-1, CS-2, CS-3 and CS-4.   
 
The  GNSS  solution  offers  best-in-class  acquisition  and  tracing  sensitivity,  Time-To-First-Fix  (TTFF)  and 
accuracy. With built-in LNA, SIM868 doesn’t need external LNA. SIM868 can track as low as -167dBm signal 
even without network assistance. The SIM868 has excellent low power consumption characteristic (acquisition 
24mA,  tracking  21mA).  SIM868  supports  various  location  and  navigation  applications,  including  autonomous 
GPS, GLONASS, BEIDOU, QZSS, SBAS (WAAS, EGNOS, GAGAN, MSAS) and A-GPS. 
 
With  a  tiny  configuration  of  17.6*15.7*2.3mm,  SIM868  can  meet  almost  all  the  space  requirements  in 
customers’ applications, such as smart phone, PDA and other mobile devices. 
 
SIM868 is a SMT+LGA package with 77 pads, and provides all hardware interfaces between the module and 
customers’ boards. 
  One 3 lines serial port and one full modem serial port; 
  GNSS Serial port 
  USB interface which can be used for debugging and upgrading firmware; 
  Audio channels which include a microphone input and two speakers output; 
 
 
 
 
 
 
Programmable general purpose input and output; 
Two SIM cards interface; 
Support GNSS function; 
33tracking/99 acquisition-channel GNSS receiver 
SD card interface; 
I2C interface; 
  ADC interface. 
 
SIM868 is designed with power saving technique so that the current consumption is as low as 0.65 mA in sleep 
mode (with GNSS engine powered down).   
SIM868 integrates  TCP/IP protocol and extended TCP/IP  AT commands  which are  very  useful for  data transfer 
applications. For details about TCP/IP applications, please refer to document [2]. 
 
 
 
SIM868_Hardware_Design_V1.01                                            8                                                                            2016-08-01