Quectel Wireless Solutions 201604M26 Users Manual
M26 Hardware Design
GSM/GPRS Module Series
Rev. M26_Hardware_Design_V1.1
Date: 2014-11-24
www.quectel.com
GSM/GPRS Module Series
M26 Hardware Design
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Copyright © Quectel Wireless Solutions Co., Ltd. 2014. All rights reserved.
M26_Hardware_Design Confidential / Released 1 / 80
About the Document
Revision
Date
Author
Description
1.0
2014-08-07
Felix YIN
Initial
1.1
2014-11-24
Felix YIN
1. Modified output power of Bluetooth
2. Modified the timing of the RFTXMON signal
3. Updated Figure 5: Reference circuit for power
supply
4. Modified description of RTC and SIM card
interface
5. Modified description of UART Application
6. Deleted the over-voltage automatic shutdown
function
7. Modified the antenna gain in the Table 24
8. Modified the current consumption information in
Section 5.3 & 5.4
History
GSM/GPRS Module Series
M26 Hardware Design
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Contents
About the Document ................................................................................................................................... 2
Contents ....................................................................................................................................................... 3
Table Index ................................................................................................................................................... 6
Figure Index ................................................................................................................................................. 7
1 Introduction .......................................................................................................................................... 9
1.1. Safety Information.................................................................................................................... 10
2 Product Concept ................................................................................................................................ 11
2.1. General Description ................................................................................................................. 11
2.2. Key Features ........................................................................................................................... 12
2.3. Functional Diagram ................................................................................................................. 14
2.4. Evaluation Board ..................................................................................................................... 14
3 Application Interface ......................................................................................................................... 15
3.1. Pin of Module ........................................................................................................................... 16
3.1.1. Pin Assignment .............................................................................................................. 16
3.1.2. Pin Description ............................................................................................................... 17
3.2. Operating Modes ..................................................................................................................... 21
3.3. Power Supply ........................................................................................................................... 22
3.3.1. Power Features of Module ............................................................................................. 22
3.3.2. Decrease Supply Voltage Drop ...................................................................................... 23
3.3.3. Reference Design For Power Supply ............................................................................ 23
3.3.4. Monitor Power Supply .................................................................................................... 24
3.4. Power On and Down Scenarios .............................................................................................. 24
3.4.1. Power On ....................................................................................................................... 24
3.4.2. Power Down ................................................................................................................... 26
3.4.2.1. Power Down Module Using the PWRKEY Pin .................................................. 26
3.4.2.2. Power Down Module Using AT Command ........................................................ 27
3.4.2.3. Under-voltage Automatic Shutdown .................................................................. 28
3.4.3. Restart ............................................................................................................................ 28
3.5. Power Saving ........................................................................................................................... 29
3.5.1. Minimum Functionality Mode ......................................................................................... 29
3.5.2. SLEEP Mode .................................................................................................................. 29
3.5.3. Wake Up Module From SLEEP Mode ........................................................................... 30
3.5.4. Summary of State Transition .......................................................................................... 30
3.6. RTC Backup............................................................................................................................. 30
3.7. Serial Interfaces ....................................................................................................................... 32
3.7.1. UART Port ...................................................................................................................... 34
3.7.1.1. The Feature of UART Port................................................................................. 34
3.7.1.2. The Connection of UART .................................................................................. 35
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3.7.1.3. Firmware Upgrade ............................................................................................. 36
3.7.2. Debug Port ..................................................................................................................... 37
3.7.3. Auxiliary UART Port ....................................................................................................... 38
3.7.4. UART Application ........................................................................................................... 38
3.8. Audio Interfaces ....................................................................................................................... 40
3.8.1. Decrease TDD Noise and other Noise .......................................................................... 41
3.8.2. Microphone Interfaces Design ....................................................................................... 41
3.8.3. Receiver and Speaker Interface Design ........................................................................ 42
3.8.4. Earphone Interface Design ............................................................................................ 44
3.8.5. Audio Characteristics ..................................................................................................... 44
3.9. PCM Interface .......................................................................................................................... 45
3.9.1. Configuration .................................................................................................................. 45
3.9.2. Timing ............................................................................................................................. 46
3.9.3. Reference Design .......................................................................................................... 48
3.9.4. AT Command ................................................................................................................. 48
3.10. SIM Card Interface................................................................................................................... 49
3.11. ADC ......................................................................................................................................... 51
3.12. Behaviors of The RI ................................................................................................................. 51
3.13. Network Status Indication ........................................................................................................ 53
3.14. RF Transmitting Signal Indication ............................................................................................ 54
4 Antenna Interface ............................................................................................................................... 56
4.1. GSM Antenna Interface ........................................................................................................... 56
4.1.1. Reference Design .......................................................................................................... 56
4.1.2. RF Output Power ........................................................................................................... 57
4.1.3. RF Receiving Sensitivity ................................................................................................ 58
4.1.4. Operating Frequencies................................................................................................... 58
4.1.5. RF Cable Soldering ........................................................................................................ 59
4.2. Bluetooth Antenna Interface .................................................................................................... 59
5 Electrical, Reliability and Radio Characteristics ............................................................................ 61
5.1. Absolute Maximum Ratings ..................................................................................................... 61
5.2. Operating Temperature ............................................................................................................ 61
5.3. Power Supply Ratings ............................................................................................................. 62
5.4. Current Consumption .............................................................................................................. 63
5.5. Electro-static Discharge ........................................................................................................... 65
6 Mechanical Dimensions .................................................................................................................... 66
6.1. Mechanical Dimensions of Module .......................................................................................... 66
6.2. Recommended Footprint ......................................................................................................... 68
6.3. Top View of the Module ........................................................................................................... 69
6.4. Bottom View of the Module ...................................................................................................... 69
7 Storage and Manufacturing .............................................................................................................. 70
7.1. Storage..................................................................................................................................... 70
7.2. Soldering .................................................................................................................................. 71
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7.3. Packaging ................................................................................................................................ 71
7.3.1. Tape and Reel Packaging .............................................................................................. 72
8 Appendix A Reference ....................................................................................................................... 73
9 Appendix B GPRS Coding Scheme ................................................................................................. 78
10 Appendix C GPRS Multi-slot Class .................................................................................................. 80
11 FCC Warning ...................................................................................................................................... 81
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Table Index
TABLE 1: MODULE KEY FEATURES ............................................................................................................... 12
TABLE 2: CODING SCHEMES AND MAXIMUM NET DATA RATES OVER AIR INTERFACE ........................ 13
TABLE 3: IO PARAMETERS DEFINITION ........................................................................................................ 17
TABLE 4: PIN DESCRIPTION ........................................................................................................................... 17
TABLE 5: OVERVIEW OF OPERATING MODES ............................................................................................. 21
TABLE 6: SUMMARY OF STATE TRANSITION ............................................................................................... 30
TABLE 7: LOGIC LEVELS OF THE UART INTERFACE .................................................................................. 33
TABLE 8: PIN DEFINITION OF THE UART INTERFACES .............................................................................. 33
TABLE 9: PIN DEFINITION OF AUDIO INTERFACE ....................................................................................... 40
TABLE 10: TYPICAL ELECTRET MICROPHONE CHARACTERISTICS ......................................................... 44
TABLE 11: TYPICAL SPEAKER CHARACTERISTICS ..................................................................................... 44
TABLE 12: PIN DEFINITION OF PCM INTERFACE ......................................................................................... 45
TABLE 13: CONFIGURATION ........................................................................................................................... 45
TABLE 14: QPCMON COMMAND DESCRIPTION .......................................................................................... 48
TABLE 15: QPCMVOL COMMAND DESCRIPTION ......................................................................................... 49
TABLE 16: PIN DEFINITION OF THE SIM INTERFACE .................................................................................. 49
TABLE 17: PIN DEFINITION OF THE ADC ...................................................................................................... 51
TABLE 18: CHARACTERISTICS OF THE ADC ................................................................................................ 51
TABLE 19: BEHAVIORS OF THE RI ................................................................................................................. 51
TABLE 20: WORKING STATE OF THE NETLIGHT .......................................................................................... 53
TABLE 21: PIN DEFINITION OF THE RFTXMON ............................................................................................ 54
TABLE 22: PIN DEFINITION OF THE RF_ANT ................................................................................................ 56
TABLE 23: ANTENNA CABLE REQUIREMENTS ............................................................................................. 57
TABLE 24: ANTENNA REQUIREMENTS .......................................................................................................... 57
TABLE 25: THE MODULE CONDUCTED RF OUTPUT POWER .................................................................... 57
TABLE 26: THE MODULE CONDUCTED RF RECEIVING SENSITIVITY ....................................................... 58
TABLE 27: THE MODULE OPERATING FREQUENCIES ................................................................................ 58
TABLE 28: PIN DEFINITION OF THE BT_ANT ................................................................................................ 59
TABLE 29: ABSOLUTE MAXIMUM RATINGS .................................................................................................. 61
TABLE 30: OPERATING TEMPERATURE ........................................................................................................ 61
TABLE 31: THE MODULE POWER SUPPLY RATINGS .................................................................................. 62
TABLE 32: THE MODULE CURRENT CONSUMPTION .................................................................................. 63
TABLE 33: THE ESD ENDURANCE (TEMPERATURE: 25ºC, HUMIDITY: 45%) ............................................ 65
TABLE 34: RELATED DOCUMENTS ................................................................................................................ 73
TABLE 35: TERMS AND ABBREVIATIONS ...................................................................................................... 74
TABLE 36: DESCRIPTION OF DIFFERENT CODING SCHEMES .................................................................. 78
TABLE 37: GPRS MULTI-SLOT CLASSES ...................................................................................................... 80
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Figure Index
FIGURE 1: MODULE FUNCTIONAL DIAGRAM ............................................................................................... 14
FIGURE 2: PIN ASSIGNMENT ......................................................................................................................... 16
FIGURE 3: VOLTAGE RIPPLE DURING TRANSMITTING .............................................................................. 22
FIGURE 4: REFERENCE CIRCUIT FOR THE VBAT INPUT ........................................................................... 23
FIGURE 5: REFERENCE CIRCUIT FOR POWER SUPPLY ............................................................................ 24
FIGURE 6: TURN ON THE MODULE WITH AN OPEN-COLLECTOR DRIVER .............................................. 25
FIGURE 7: TURN ON THE MODULE WITH A BUTTON .................................................................................. 25
FIGURE 8: TURN-ON TIMING .......................................................................................................................... 26
FIGURE 9: TURN-OFF TIMING ........................................................................................................................ 27
FIGURE 10: TIMING OF RESTARTING SYSTEM ............................................................................................ 28
FIGURE 11: VRTC IS SUPPLIED BY A NON-CHARGEABLE BATTERY ........................................................ 31
FIGURE 12: VRTC IS SUPPLIED BY A RECHARGEABLE BATTERY ............................................................ 31
FIGURE 13: VRTC IS SUPPLIED BY A CAPACITOR ...................................................................................... 32
FIGURE 14: REFERENCE DESIGN FOR FULL-FUNCTION UART ................................................................ 35
FIGURE 15: REFERENCE DESIGN FOR UART PORT ................................................................................... 36
FIGURE 16: REFERENCE DESIGN FOR UART PORT WITH HARDWARE FLOW CONTROL .................... 36
FIGURE 17: REFERENCE DESIGN FOR FIRMWARE UPGRADE ................................................................. 37
FIGURE 18: REFERENCE DESIGN FOR DEBUG PORT ............................................................................... 37
FIGURE 19: REFERENCE DESIGN FOR AUXILIARY UART PORT ............................................................... 38
FIGURE 20: LEVEL MATCH DESIGN FOR 3.3V SYSTEM .............................................................................. 38
FIGURE 21: SKETCH MAP FOR RS-232 INTERFACE MATCH ...................................................................... 39
FIGURE 22: REFERENCE DESIGN FOR AIN ................................................................................................. 41
FIGURE 23: HANDSET INTERFACE DESIGN FOR AOUT1 ........................................................................... 42
FIGURE 24: SPEAKER INTERFACE DESIGN WITH AN AMPLIFIER FOR AOUT1 ....................................... 42
FIGURE 25: HANDSET INTERFACE DESIGN FOR AOUT2 ........................................................................... 43
FIGURE 26: SPEAKER INTERFACE DESIGN WITH AN AMPLIFIER FOR AOUT2 ....................................... 43
FIGURE 27: EARPHONE INTERFACE DESIGN .............................................................................................. 44
FIGURE 28: LONG SYNCHRONIZATION & SIGN EXTENSION DIAGRAM ................................................... 46
FIGURE 29: LONG SYNCHRONIZATION & ZERO PADDING DIAGRAM....................................................... 47
FIGURE 30: SHORT SYNCHRONIZATION & SIGN EXTENSION DIAGRAM ................................................. 47
FIGURE 31: SHORT SYNCHRONIZATION & ZERO PADDING DIAGRAM .................................................... 47
FIGURE 32: REFERENCE DESIGN FOR PCM ............................................................................................... 48
FIGURE 33: REFERENCE CIRCUIT FOR SIM INTERFACE WITH THE 6-PIN SIM CARD HOLDER ........... 50
FIGURE 34: RI BEHAVIOR OF VOICE CALLING AS A RECEIVER ................................................................ 52
FIGURE 35: RI BEHAVIOR AS A CALLER ....................................................................................................... 52
FIGURE 36: RI BEHAVIOR OF URC OR SMS RECEIVED ............................................................................. 52
FIGURE 37: REFERENCE DESIGN FOR NETLIGHT ..................................................................................... 53
FIGURE 38: RFTXMON SIGNAL DURING BURST TRANSMISSION ............................................................. 54
FIGURE 39: RFTXMON SIGNAL DURING CALL ............................................................................................. 55
FIGURE 40: REFERENCE DESIGN FOR GSM ANTENNA ............................................................................. 56
FIGURE 41: RF SOLDERING SAMPLE ........................................................................................................... 59
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FIGURE 42: REFERENCE DESIGN FOR BLUETOOTH ANTENNA ............................................................... 60
FIGURE 43: M26 MODULE TOP AND SIDE DIMENSIONS (UNIT: MM) ......................................................... 66
FIGURE 44: M26 MODULE BOTTOM DIMENSIONS (UNIT: MM) ................................................................... 67
FIGURE 45: RECOMMENDED FOOTPRINT (UNIT: MM) ................................................................................ 68
FIGURE 46: TOP VIEW OF THE MODULE ...................................................................................................... 69
FIGURE 47: BOTTOM VIEW OF THE MODULE .............................................................................................. 69
FIGURE 48: RAMP-SOAK-SPIKE REFLOW PROFILE .................................................................................... 71
FIGURE 49: TAPE AND REEL SPECIFICATION .............................................................................................. 72
FIGURE 50: DIMENSIONS OF REEL ............................................................................................................... 72
FIGURE 51: RADIO BLOCK STRUCTURE OF CS-1, CS-2 AND CS-3 ........................................................... 78
FIGURE 52: RADIO BLOCK STRUCTURE OF CS-4 ....................................................................................... 79
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GSM/GPRS Module Series
M26 Hardware Design
1 Introduction
This document defines the M26 module and describes its hardware interface which are connected with
the customer application and the air interface.
This document can help you quickly understand module interface specifications, electrical and
mechanical details. Associated with application note and user guide, you can use M26 module to design
and set up mobile applications easily.
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GSM/GPRS Module Series
Full attention must be given to driving at all times in order to reduce the risk of an
accident. Using a mobile while driving (even with a handsfree kit) cause distraction
and can lead to an accident. You must comply with laws and regulations restricting
the use of wireless devices while driving.
Switch off the cellular terminal or mobile before boarding an aircraft. Make sure it
switched off. The operation of wireless appliances in an aircraft is forbidden to
prevent interference with communication systems. Consult the airline staff about
the use of wireless devices on boarding the aircraft, if your device offers a Airplane
Mode which must be enabled prior to boarding an aircraft.
Switch off your wireless device when in hospitals or clinics or other health care
facilities. These requests are desinged to prevent possible interference with
sentitive medical equipment.
Cellular terminals or mobiles operate over radio frequency signal and cellular
network and cannot be guaranteed to connect in all conditions, for example no
mobile fee or an invalid SIM card. While you are in this condition and need
emergent help, please remember using emergency call. In order to make or
receive call, the cellular terminal or mobile must be switched on and in a service
area with adequate cellular signal strength.
Your cellular terminal or mobile contains a transmitter and receiver. When it is ON ,
it receives and transmits radio frequency energy. RF interference can occur if it is
used close to TV set, radio, computer or other electric equipment.
In locations with potencially explosive atmospheres, obey all posted signs to turn
off wireless devices such as your phone or other cellular terminals. Areas with
potencially exposive atmospheres including fuelling areas, below decks on boats,
fuel or chemical transfer or storage facilities, areas where the air contains
chemicals or particles such as grain, dust or metal powders.
M26 Hardware Design
1.1. Safety Information
The following safety precautions must be observed during all phases of the operation, such as usage,
service or repair of any cellular terminal or mobile incorporating M26 module. Manufacturers of the
cellular terminal should send the following safety information to users and operating personnel and to
incorporate these guidelines into all manuals supplied with the product. If not so, Quectel does not take on
any liability for customer failure to comply with these precautions.
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GSM/GPRS Module Series
M26 Hardware Design
2 Product Concept
2.1. General Description
M26 is a Quad-band GSM/GPRS engine that works at frequencies of GSM850MHz, EGSM900MHz,
DCS1800MHz and PCS1900MHz. The M26 features GPRS multi-slot class 12 and supports the GPRS
coding schemes CS-1, CS-2, CS-3 and CS-4. For more details about GPRS multi-slot classes and coding
schemes, please refer to the Appendix B & C.
With a tiny profile of 15.8mm × 17.7mm × 2.3mm, the module can meet almost all the requirements for
M2M applications, including Vehicles and Personal Tracking, Security System, Wireless POS, Industrial
PDA, Smart Metering, and Remote Maintenance& Control, etc.
M26 is an SMD type module with LCC package, which can be easily embedded into applications. It
provides abundant hardware interfaces like PCM Interface.
Designed with power saving technique, the current consumption of M26 is as low as 1.3 mA in SLEEP
mode when DRX is 5.
M26 is integrated with Internet service protocols, such as TCP/UDP, FTP and PPP. Extended AT
commands have been developed for you to use these Internet service protocols easily.
M26 supports Bluetooth interface, it is fully compliant with Bluetooth specification 3.0.
The module fully complies with the RoHS directive of the European Union.
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GSM/GPRS Module Series
Feature
Implementation
Power Supply
Single supply voltage: 3.3V ~ 4.6V
Typical supply voltage: 4V
Power Saving
Typical power consumption in SLEEP mode: 1.3 mA @DRX=5
1.2 mA @DRX=9
Frequency Bands
Quad-band: GSM850, EGSM900, DCS1800, PCS1900.
The module can search these frequency bands automatically
The frequency bands can be set by AT command
Compliant to GSM Phase 2/2+
GSM Class
Small MS
Transmitting Power
Class 4 (2W) at GSM850 and EGSM900
Class 1 (1W) at DCS1800 and PCS1900
GPRS Connectivity
GPRS multi-slot class 12 (default)
GPRS multi-slot class 1~12 (configurable)
GPRS mobile station class B
DATA GPRS
GPRS data downlink transfer: max. 85.6kbps
GPRS data uplink transfer: max. 85.6kbps
Coding scheme: CS-1, CS-2, CS-3 and CS-4
Support the protocols PAP (Password Authentication Protocol)
usually used for PPP connections
Internet service protocols TCP/UDP, FTP, PPP, HTTP, NTP, PING
Support Packet Broadcast Control Channel (PBCCH)
Support Unstructured Supplementary Service Data (USSD)
Temperature Range
Normal operation: -35°C ~ +80°C
Restricted operation: -40°C ~ -35°C and +80°C ~ +85°C 1)
Storage temperature: -45°C ~ +90°C
Bluetooth
Support Bluetooth specification 3.0
Output Power: Class 1 (Typical 7.5dBm)
SMS
Text and PDU mode
SMS storage: SIM card
SIM Interface
Support SIM card: 1.8V, 3.0V
Audio Features
Speech codec modes:
Half Rate (ETS 06.20)
Full Rate (ETS 06.10)
M26 Hardware Design
2.2. Key Features
The following table describes the detailed features of M26 module.
Table 1: Module Key Features
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GSM/GPRS Module Series
1)
When the module works within this temperature range, the deviations from the GSM specification may
occur. For example, the frequency error or the phase error will be increased.
Enhanced Full Rate (ETS 06.50/06.60/06.80)
Adaptive Multi-Rate (AMR)
Echo Suppression
Noise Reduction
UART Interfaces
UART Port:
Seven lines on UART port interface
Used for AT command, GPRS data
Multiplexing function
Support autobauding from 4800bps to 115200bps
Debug Port:
Two lines on debug port interface DBG_TXD and DBG_RXD
Debug Port only used for firmware debugging
Auxiliary Port:
Used for AT command
Phonebook Management
Support phonebook types: SM, ME, ON, MC, RC, DC, LD, LA
SIM Application Toolkit
Support SAT class 3, GSM 11.14 Release 99
Real Time Clock
Supported
Physical Characteristics
Size: 15.8±0.15 × 17.7±0.15 × 2.3±0.2mm
Weight: Approx. 1.3g
Firmware Upgrade
Firmware upgrade via UART Port
Antenna Interface
Connected to antenna pad with 50 Ohm impedance control
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
NOTE
M26 Hardware Design
Table 2: Coding Schemes and Maximum Net Data Rates over Air Interface
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GSM/GPRS Module Series
BB&RF
RF PAM
26MHzRF Transceiver
RTC
AUDIO
Serial
Interface
SIM
Interface
RF_ANT
VBAT
PWRKEY
VRTC
NETLIGHT
UART
SIM
Interface
ESD
PMU
MEMORY
BT_ANT
PWM
AUDIO
PCM
PCM
ADC
ADC
BT
VDD_EXT
VDD_EXT
M26 Hardware Design
2.3. Functional Diagram
The following figure shows a block diagram of M26 and illustrates the major functional parts.
Radio frequency part
Power management
The peripheral interface
—Power supply
—Turn-on/off interface
—UART interface
—Audio interface
—PCM interface
—SIM interface
—ADC interface
—RF interface
—BT interface
Figure 1: Module Functional Diagram
2.4. Evaluation Board
In order to help you to develop applications with M26, Quectel supplies an evaluation board (EVB),
RS-232 to USB cable, power adapter, earphone, antenna and other peripherals to control or test the
module. For details, please refer to the document [11].
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GSM/GPRS Module Series
M26 Hardware Design
3 Application Interface
The module adopts LCC package and has 44 pins. The following chapters provide detailed descriptions
about these pins.
Pin of module
Operating modes
Power supply
Power on/down
Power saving
RTC
Serial interfaces
Audio interfaces
PCM interface
SIM card interface
ADC
Behaviors of the RI
Network status indication
RF transmitting signal indication
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GSM/GPRS Module Series
AGND
SPK2P
MICP
MICN
SPK1P
SPK1N
PWRKEY
SIM_RST
SIM_CLK
CTS
VRTC
VBAT
GND
GND
DBG_TXD
DBG_RXD
GND
GND
RF_ANT
14
M26
Top View
15
16
17
18
19
20
21
22
36
37
38
39
40
41
42
43
44
1
2
3
4
5
6
7
8
9
10
11
12
13
23
24
25
26
27
28
29
30
31
32
33
34
35
AVDD
ADC0
SIM_GND
SIM_DATA
GND
PCM_OUT
PCM_IN
PCM_SYNC
PCM_CLK
TXD_AUX
RXD_AUX
GND
BT_ANT
RFTXMON
VDD_EXT
RTS
DCD
RI
DTR
TXD
RXD
NETLIGHT
RESERVED
SIM_VDD
VBAT
POWER
GND AUDIO
UART
SIM
PCM
ANT
OTHERS
RESERVED
Keep all reserved pins open.
NOTE
M26 Hardware Design
3.1. Pin of Module
3.1.1. Pin Assignment
Figure 2: Pin Assignment
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GSM/GPRS Module Series
Type
Description
IO
Bidirectional input/output
DI
Digital input
DO
Digital output
PI
Power input
PO
Power output
AI
Analog input
AO
Analog output
Power Supply
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
VBAT
42,43
PI
Main power supply of
module:
VBAT=3.3V~4.6V
VImax=4.6V
VImin=3.3V
VInorm=4.0V
Make sure that
supply
sufficient
current in a
transmitting
burst typically
rises to 1.6A.
VRTC
44
IO
Power supply for RTC when
VBAT is not supplied for the
system.
Charging for backup battery or
golden capacitor when the
VBAT is applied.
VImax=3.3V
VImin=1.5V
VInorm=2.8V
VOmax=3V
VOmin=2V
VOnorm=2.8V
IOmax=2mA
Iin≈10uA
If unused, keep
this pin open.
VDD_
EXT
24
PO
Supply 2.8V voltage for
external circuit.
VOmax=2.9V
VOmin=2.7V
VOnorm=2.8V
IOmax=20mA
1. If unused,
keep this pin
open.
2. Recommend
to add a
M26 Hardware Design
3.1.2. Pin Description
Table 3: IO Parameters Definition
Table 4: Pin Description
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GSM/GPRS Module Series
2.2~4.7uF
bypass
capacitor,
when using
this pin for
power supply.
GND
27,34
36,37
40,41
Ground
Turn on/off
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
PWRKEY
7
DI
Power on/off key. PWRKEY
should be pulled down for a
moment to turn on or turn off
the system.
VILmax=
0.1×VBAT
VIHmin=
0.6×VBAT
VIHmax=3.1V
Audio Interface
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
MICP
MICN
3,
4
AI
Positive and negative voice
input
Refer to Section 3.8
If unused, keep
these pins
open.
SPK1P
SPK1N
5,
6
AO
Channel 1 positive and
negative voice output
If unused, keep
these pins
open.
Support both
voice and
ringtone
output.
SPK2P
2
AO
Channel 2 voice output
AGND
1
Analog ground. Separate
ground connection for
external audio circuits.
If unused, keep
this pin open.
Network Status Indicator
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
NETLIGHT
16
DO
Network status indication
VOHmin=
0.85×VDD_EXT
VOLmax=
0.15×VDD_EXT
If unused,
keep this pin
open.
UART Port
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
M26 Hardware Design
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GSM/GPRS Module Series
TXD
18
DO
Transmit data
VILmin=0V
VILmax=
0.25×VDD_EXT
VIHmin=
0.75×VDD_EXT
VIHmax=
VDD_EXT+0.2
VOHmin=
0.85×VDD_EXT
VOLmax=
0.15×VDD_EXT
If only use
TXD, RXD and
GND to
communicate,
recommended
to keep other
pins open.
RXD
17
DI
Receive data
DTR
19
DI
Data terminal ready
RI
20
DO
Ring indication
DCD
21
DO
Data carrier detection
CTS
22
DO
Clear to send
RTS
23
DI
Request to send
Debug Port
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
DBG_
TXD
39
DO
Transmit data
Same as above
If unused,
keep these
pins open.
DBG_
RXD
38
DI
Receive data
Auxiliary Port
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
TXD_
AUX
29
DO
Transmit data
Same as above
If unused,
keep these
pins open.
RXD_
AUX
28
DI
Receive data
SIM Interface
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
SIM_ VDD
14
PO
Power supply for SIM card
The voltage can be
selected by software
automatically. Either
1.8V or 3.0V.
All signals of
SIM interface
should be
protected
against ESD
with a TVS
diode array.
Maximum
trace length is
200mm from
the module
pad to SIM
card holder.
SIM_ CLK
13
DO
SIM clock
VOLmax=
0.15×SIM_VDD
VOHmin=
0.85×SIM_VDD
SIM_ DATA
11
IO
SIM data
VILmax=
0.25×SIM_VDD
VIHmin=
0.75×SIM_VDD
VOLmax=
0.15×SIM_VDD
VOHmin=
0.85×SIM_VDD
M26 Hardware Design
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GSM/GPRS Module Series
SIM_ RST
12
DO
SIM reset
VOLmax=
0.15×SIM_VDD
VOHmin=
0.85×SIM_VDD
SIM_
GND
10 SIM ground
ADC
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
AVDD
8
PO
Reference voltage of
ADC circuit
VOmax=2.9V
VOmin=2.7V
VOnorm=2.8V
If unused,
keep this pin
open.
ADC0
9
AI
General purpose analog to
digital converter.
Voltage range:
0V to 2.8V
If unused,
keep this pin
open.
PCM
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
PCM_ CLK
30
DO
PCM clock
VILmin= 0V
VILmax=
0.25×VDD_EXT
VIHmin=
0.75×VDD_EXT
VIHmax=
VDD_EXT+0.2
VOHmin=
0.85×VDD_EXT
VOLmax=
0.15×VDD_EXT
If unused,
keep this pin
open.
PCM_
SYNC
31
DO
PCM frame
synchronization
PCM_
IN
32
DI
PCM data input
PCM_
OUT
33
DO
PCM data output
Antenna Interface
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
RF_
ANT
35
IO
GSM antenna pad
Impedance of 50Ω
BT_
ANT
26
IO
BT antenna pad
Impedance of 50Ω
If unused,
keep this pin
open.
Transmitting Signal Indication
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
RFTXMON
25
DO
Transmission signal
indication
VOHmin=
0.85×VDD_EXT
VOLmax=
If unused,
keep this pin
open.
M26 Hardware Design
M26_Hardware_Design Confidential / Released 20 / 80
GSM/GPRS Module Series
0.15×VDD_EXT
Other Interface
PIN Name
PIN No.
I/O
Description
DC Characteristics
Comment
RESERVED
15
Keep these
pins open.
Mode
Function
Normal Operation
GSM/GPRS
Sleep
After enabling sleep mode by AT+QSCLK=1, the module will
automatically enter into Sleep Mode if DTR is set to high level
and there is no interrupt (such as GPIO interrupt or data on
UART port). In this case, the current consumption of module
will reduce to the minimal level.
During Sleep Mode, the module can still receive paging
message and SMS from the system normally.
GSM IDLE
Software is active. The module has registered to the GSM
network, and the module is ready to send and receive GSM
data.
GSM TALK
GSM connection is ongoing. In this mode, the power
consumption is decided by the configuration of Power Control
Level (PCL), dynamic DTX control and the working RF band.
GPRS IDLE
The module is not registered to GPRS network. The module is
not reachable through GPRS channel.
GPRS
STANDBY
The module is registered to GPRS network, but no GPRS PDP
context is active. The SGSN knows the Routing Area where the
module is located at.
GPRS READY
The PDP context is active, but no data transfer is ongoing. The
module is ready to receive or send GPRS data. The SGSN
knows the cell where the module is located at.
GPRS DATA
There is GPRS data in transfer. In this mode, power
consumption is decided by the PCL, working RF band and
GPRS multi-slot configuration.
M26 Hardware Design
3.2. Operating Modes
The table below briefly summarizes the various operating modes in the following chapters.
Table 5: Overview of Operating Modes
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GSM/GPRS Module Series
Vdrop
4.615ms
577us
IBAT
VBAT
Burst:1.6A
POWER DOWN
Normal shutdown by sending the AT+QPOWD=1 command or using the
PWRKEY pin. The power management ASIC disconnects the power supply from
the base band part of the module, and only the power supply for the RTC is
remained. Software is not active. The UART interfaces are not accessible.
Operating voltage (connected to VBAT) remains applied.
Minimum
Functionality Mode
(without removing
power supply)
AT+CFUN command can set the module to a minimum functionality mode
without removing 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
disabled, but the UART port is still accessible. The power consumption in this
case is very low.
M26 Hardware Design
3.3. Power Supply
3.3.1. Power Features of Module
The power supply is one of the key issues in designing GSM terminals. Because of the 577us radio burst
in GSM every 4.615ms, power supply must be able to deliver high current peaks in a burst period. During
these peaks, drops on the supply voltage must not exceed minimum working voltage of module.
For the M26 module, the max current consumption could reach to 1.6A during a burst transmission. It will
cause a large voltage drop on the VBAT. In order to ensure stable operation of the module, it is
recommended that the max voltage drop during the burst transmission does not exceed 400mV.
Figure 3: Voltage Ripple during Transmitting
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GSM/GPRS Module Series
VBAT
C2C1
+
C3 C4
GND
100uF 100nF 10pF
0603
33pF
0603
M26 Hardware Design
3.3.2. Decrease Supply Voltage Drop
The power supply range of the module is 3.3V to 4.6V. Make sure that the input voltage will never drop
below 3.3V even in a burst transmission. If the power voltage drops below 3.3V, the module could turn off
automatically. For better power performance, it is recommended to place a 100uF tantalum capacitor with
low ESR (ESR=0.7Ω) and ceramic capacitor 100nF, 33pF and 10pF near the VBAT pin. The reference
circuit is illustrated in Figure 4.
The VBAT route should be wide enough to ensure that there is not too much voltage drop during burst
transmission. The width of trace should be no less than 2mm and the principle of the VBAT route is the
longer route, the wider trace.
3.3.3. Reference Design For Power Supply
The power design for the module is very important, since the performance of power supply for the module
largely depends on the power source. The power supply is capable of providing the sufficient current up to
2A at least. If the voltage drop between the input and output is not too high, it is suggested to use a LDO
as module’s power supply. If there is a big voltage difference between the input source and the desired
output (VBAT), a switcher power converter is recommended to use as a power supply.
The following figure shows a reference design for +5V input power source. The designed output for the
power supply is 4.0V and the maximum load current is 3A. In addition, in order to get a stable output
voltage, a zener diode is placed close to the pins of VBAT. As to the zener diode, it is suggested to use a
zener diode whose reverse zener voltage is 5.1V and dissipation power is more than 1 Watt.
Figure 4: Reference Circuit for the VBAT Input
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GSM/GPRS Module Series
DC_IN
C1
C2
MIC29302WU U1
IN OUT
EN
GND
ADJ
2 4
1
3
5
VBAT
100nF
C3
470uFC4100nF
R2
D1
124K
56K
R3
470uF
5.1V
R4
470R
MCU_POWER_ON/OFF
47K
4.7K
R5
R6
R1
51K
It is suggested to control the module’s main power supply (VBAT) via LDO enable pin to restart the
module when the module has become abnormal. Power switch circuit like P-channel MOSFET switch
circuit can also be used to control VBAT.
NOTE
M26 Hardware Design
Figure 5: Reference Circuit for Power Supply
3.3.4. Monitor Power Supply
The command ―AT+CBC‖ can be used to monitor the supply voltage of the module. The unit of the
displayed voltage is mV.
For details, please refer to the document [1].
3.4. Power On and Down Scenarios
3.4.1. Power On
The module can be turned on by driving the pin PWRKEY to a low level voltage. An open collector driver
circuit is suggested to control the PWRKEY. A simple reference circuit is illustrated as below.
M26_Hardware_Design Confidential / Released 24 / 80
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