SimTech SIMCom SIM800C Supplement

SIM800C_Hardware_Design_V1.00

Smart Machine Smart Decision
SIM800C_Hardware_Design_V1.00 2 2014-10-30
Document Title
SIM800C Hardware Design
Version
V1.00
Date
2014-10-30
Status
Draft
Document Control ID
SIM800C_Hardware_Design_V1.00
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. 2014

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Contents
Version History............................................................................................................8
1. Introduction..........................................................................................................9
2. SIM800C Overview .............................................................................................9
2.1. SIM800C...............................................................................................................................9
2.2. SIM800C Key Features.........................................................................................................9
2.3. Operating Mode ..................................................................................................................11
2.4. Functional Diagram.............................................................................................................11
3. Package Information.........................................................................................13
3.1. Pin Out Diagram .................................................................................................................13
3.2. Pin Description....................................................................................................................14
3.3. Package Dimensions ...........................................................................................................15
4. Application Interface.........................................................................................17
4.1. Power Supply......................................................................................................................17
4.1.1. Power Supply Pin................................................................................................................................ 18
4.1.2. Monitoring Power Supply................................................................................................................... 19
4.2. Power on/down Scenarios...................................................................................................19
4.2.1. Power on SIM800C............................................................................................................................. 19
4.2.2. Power down SIM800C........................................................................................................................ 20
4.3. Power Saving Mode............................................................................................................22
4.3.1. Minimum Functionality Mode............................................................................................................ 22
4.3.2. Sleep Mode 1 (AT+CSCLK=1).......................................................................................................... 23
4.3.3. Wake Up SIM800C from Sleep Mode 1............................................................................................. 23
4.3.4. Sleep Mode 2 (AT+CSCLK=2).......................................................................................................... 23
4.3.5. Wake Up SIM800C from Sleep Mode 2............................................................................................. 23
4.4. Power Saving Mode............................................................................................................24
4.5. Serial Port and USB Interface.............................................................................................25
4.5.1 Function of Serial Port........................................................................................................................ 25
4.5.2 Serial Interfaces................................................................................................................................... 26
4.5.3 Debug Interface................................................................................................................................... 28
4.5.4 Software Upgrade................................................................................................................................ 29
4.6. UART1_RI Behaviors.........................................................................................................29
4.7. Audio Interfaces..................................................................................................................31
4.7.1. Speaker Interfaces Configuration........................................................................................................ 31
4.7.2. Microphone Interfaces Configuration................................................................................................. 32
4.7.3. Audio Electronic Characteristic .......................................................................................................... 32
4.7.4. TDD .................................................................................................................................................... 33
4.8. SIM Card Interface..............................................................................................................33
4.8.1. SIM Card Application ......................................................................................................................... 33

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4.8.2. SIM Card Design Guide...................................................................................................................... 34
4.8.3. Design Considerations for SIM Card Holder...................................................................................... 35
4.9. ADC....................................................................................................................................36
4.10. Network Status Indication...................................................................................................37
4.10.1. NETLIGHT Multiplexing Function................................................................................................. 38
4.11. Operating Status Indication.................................................................................................38
4.11.1. STATUS Multiplexing Function...................................................................................................... 38
4.12. RF Synchronization Signal .................................................................................................38
4.12.1. RF_SYNC Multiplexing Function................................................................................................... 39
4.13. Antenna Interface................................................................................................................39
4.13.1 GSM Antenna Interface................................................................................................................... 39
5. PCB Layout........................................................................................................41
5.1 Pin Assignment...................................................................................................................41
5.2 Principle of PCB Layout.....................................................................................................41
5.2.1 Antenna Interface................................................................................................................................ 42
5.2.2 Power Supply...................................................................................................................................... 42
5.2.3 SIM Card Interface.............................................................................................................................. 42
5.2.4 Audio Interface.................................................................................................................................... 42
5.2.5 Others.................................................................................................................................................. 42
6. Electrical, Reliability and Radio Characteristics...........................................43
6.1 Absolute Maximum Ratings ...............................................................................................43
6.2 Recommended Operating Conditions.................................................................................43
6.3 Digital Interface Characteristics..........................................................................................43
6.4 SIM Card Interface Characteristics.....................................................................................43
6.5 SIM_VDD Characteristics..................................................................................................44
6.6 VDD_EXT Characteristics..................................................................................................44
6.7 VRTC Characteristics .........................................................................................................44
6.8 Current Consumption (VBAT=4.0V).................................................................................44
6.9 Electro-Static Discharge......................................................................................................45
6.10 Radio Characteristics ..........................................................................................................46
6.10.1 Module RF Output Power................................................................................................................ 46
6.10.2 Module RF Receive Sensitivity....................................................................................................... 47
6.10.3 Module Operating Frequencies........................................................................................................ 47
7. Manufacturing ...................................................................................................48
7.1. Top and Bottom View of SIM800C....................................................................................48
7.2. Typical Solder Reflow Profile ............................................................................................48
7.3. The Moisture Sensitivity Level...........................................................................................49
7.4. Baking Requirements..........................................................................................................49
8. Appendix.............................................................................................................50
I. Related Documents .............................................................................................................50
II. Multiplexing Function.........................................................................................................51
III. Terms and Abbreviations ....................................................................................................51

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IV. Safety Caution.....................................................................................................................53

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Table Index
TABLE 1: MODULE INFORMATION .............................................................................................................................9
TABLE 2: SIM800C KEY FEATURES .............................................................................................................................9
TABLE 3: CODING SCHEMES AND MAXIMUM NET DATA RATES OVER AIR INTERFACE ............................10
TABLE 4: OVERVIEW OF OPERATING MODES........................................................................................................11
TABLE 5: PIN DESCRIPTION .......................................................................................................................................14
TABLE 6: RECOMMENDED ZENER DIODE ..............................................................................................................17
TABLE 7: THE CURRENT CONSUMPTION OF MINIMUM FUNCTIONALITY MODE (BS-PA-MFRMS=9)......23
TABLE 8: SERIAL PORT AND USB PIN DEFINITION...............................................................................................25
TABLE 9: SERIAL PORT CHARACTERISTICS...........................................................................................................25
TABLE 10: USB_VBUS OPERATION VOLTAGE ........................................................................................................28
TABLE 11: RI BEHAVIORS............................................................................................................................................29
TABLE 12: AUDIO INTERFACE DEFINITION............................................................................................................31
TABLE 13: PERFORMANCE OF AUDIO AMPLIFIER................................................................................................31
TABLE 14: MICROPHONE INPUT CHARACTERISTICS...........................................................................................32
TABLE 15: AUDIO OUTPUT CHARACTERISTICS....................................................................................................33
TABLE 16: SIM PIN DEFINITION.................................................................................................................................33
TABLE 17: PIN DESCRIPTION (MOLEX SIM CARD HOLDER) ..............................................................................35
TABLE 18: PIN DESCRIPTION (AMPHENOL SIM CARD HOLDER).......................................................................36
TABLE 19: PIN DEFINITION OF THE ADC.................................................................................................................36
TABLE 20: ADC SPECIFICATION ................................................................................................................................37
TABLE 21: PIN DEFINITION OF THE NETLIGHT .....................................................................................................37
TABLE 22: STATUS OF THE NETLIGHT PIN..............................................................................................................37
TABLE 23: NETLIGHT MULTIPLEXING FUNCTION................................................................................................38
TABLE 24: PIN DEFINITION OF THE STATUS...........................................................................................................38
TABLE 25: STATUS MULTIPLEXING FUNCTION.....................................................................................................38
TABLE 26: DEFINITION OF THE RF_SYNC PIN........................................................................................................38
TABLE 27: RF_SYNC MULTIPLEXING FUNCTION..................................................................................................39
TABLE 28: ABSOLUTE MAXIMUM RATINGS...........................................................................................................43
TABLE 29: RECOMMENDED OPERATING CONDITIONS.......................................................................................43
TABLE 30: DIGITAL INTERFACE CHARACTERISTICS...........................................................................................43
TABLE 31: SIM CARD INTERFACE CHARACTERISTICS........................................................................................43
TABLE 32: SIM_VDD CHARACTERISTICS................................................................................................................44
TABLE 33: VDD_EXT CHARACTERISTICS ...............................................................................................................44
TABLE 34: VRTC CHARACTERISTICS.......................................................................................................................44
TABLE 35: CURRENT CONSUMPTION ......................................................................................................................44
TABLE 36: THE ESD CHARACTERISTICS (TEMPERATURE: 25℃, HUMIDITY: 45 %).......................................45
TABLE 37: GSM850 AND EGSM900 CONDUCTED RF OUTPUT POWER..............................................................46
TABLE 38: DCS1800 AND PCS1900 CONDUCTED RF OUTPUT POWER...............................................................46
TABLE 39: CONDUCTED RF RECEIVE SENSITIVITY.............................................................................................47
TABLE 40: OPERATING FREQUENCIES.....................................................................................................................47
TABLE 41: MOISTURE SENSITIVITY LEVELAND FLOOR LIFE...........................................................................49
TABLE 42: BAKING REQUIREMENTS .......................................................................................................................49
TABLE 43: RELATED DOCUMENTS ...........................................................................................................................50
TABLE 44: MULTIPLEXING FUNCTION ....................................................................................................................51
TABLE 45: TERMS AND ABBREVIATIONS................................................................................................................51
TABLE 46: SAFETY CAUTION.....................................................................................................................................53

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Figure Index
FIGURE 1: SIM800C FUNCTIONAL DIAGRAM.........................................................................................................12
FIGURE 2: PIN ASSIGNMENT (TOP VIEW)................................................................................................................13
FIGURE 3: DIMENSIONS OF SIM800C (UNIT: MM) .................................................................................................15
FIGURE 4: RECOMMENDED PCB FOOTPRINT OUTLINE (UNIT: MM)................................................................16
FIGURE 5: REFERENCE CIRCUIT OF THE VBAT INPUT.........................................................................................17
FIGURE 6: REFERENCE CIRCUIT OF THE LDO POWER SUPPLY.........................................................................17
FIGURE 7: REFERENCE CIRCUIT OF THE DC-DC POWER SUPPLY.....................................................................18
FIGURE 8: VBAT VOLTAGE DROP DURING TRANSMIT BURST...........................................................................18
FIGURE 9: THE MINIMAL VBAT VOLTAGE REQUIREMENT AT VBAT DROP ....................................................19
FIGURE 10: POWERED ON/DOWN MODULE USING TRANSISTOR.....................................................................19
FIGURE 11: POWERED ON/DOWN MODULE USING BUTTON .............................................................................19
FIGURE 12: TIMING OF POWER ON MODULE.........................................................................................................20
FIGURE 13: TIMING OF POWER DOWN SIM800C BY PWRKEY ...........................................................................21
FIGURE 14: TIMING OF RESTART SIM800C..............................................................................................................22
FIGURE 15: RTC SUPPLY FROM CAPACITOR...........................................................................................................24
FIGURE 16: RTC SUPPLY FROM NON-CHARGEABLE BATTERY..........................................................................24
FIGURE 17: RTC SUPPLY FROM RECHARGEABLE BATTERY ..............................................................................24
FIGURE 18: CONNECTION OF THE SERIAL INTERFACES.....................................................................................26
FIGURE 19: RESISTOR MATCHING CIRCUIT ...........................................................................................................27
FIGURE 20 : DIODE ISOLATION CIRCUIT.................................................................................................................27
FIGURE 21: TX LEVEL MATCHING CIRCUIT ...........................................................................................................27
FIGURE 22: RX LEVEL MATCHING CIRCUIT...........................................................................................................28
FIGURE 23: USB REFERENCE CIRCUIT ....................................................................................................................28
FIGURE 24: CONNECTION FOR SOFTWARE UPGRADING AND DEBUGGING..................................................29
FIGURE 25: UART1_RI BEHAVIOUR OF VOICE CALLING AS ARECEIVER .......................................................30
FIGURE 26: UART1_RI BEHAVIOUR OF DATA CALLING ASA RECEIVER.........................................................30
FIGURE 27: UART1_RI BEHAVIOUR OF URC OR RECEIVE SMS..........................................................................30
FIGURE 28: UART1_RI BEHAVIOUR AS A CALLER.................................................................................................31
FIGURE 29: SPEAKER REFERENCE CIRCUIT ..........................................................................................................32
FIGURE 30: MICROPHONE REFERENCE CIRCUIT..................................................................................................32
FIGURE 31: REFERENCE CIRCUIT OF THE 8-PIN SIM CARD HOLDER...............................................................34
FIGURE 32: REFERENCE CIRCUIT OF THE 6-PIN SIM CARD HOLDER...............................................................34
FIGURE 33: MOLEX 91228 SIM CARD HOLDER.......................................................................................................35
FIGURE 34: AMPHENOL C707 10M006 512 SIM CARD HOLDER...........................................................................36
FIGURE 35: REFERENCE CIRCUIT OF NETLIGHT...................................................................................................37
FIGURE 36: RF_SYNC SIGNAL DURING TRANSMIT BURST ................................................................................39
FIGURE 37: GSM ANTENNA MATCHING CIRCUIT..................................................................................................39
FIGURE 38: GSM ANTENNA MATCHING CIRCUIT WITHOUT RF CONNECTOR ...............................................40
FIGURE 40: PIN ASSIGNMENT....................................................................................................................................41
FIGURE 41: TOPAND BOTTOM VIEW OF SIM800C ................................................................................................48
FIGURE 42: TYPICAL SOLDER REFLOW PROFILE OF LEAD-FREE PROCESSES..............................................48

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Version History
Date
Version
Description of change
Author
2014-10-30
1.00
Origin
Yanwu.wang;
Xiaobo.bai

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1. Introduction
This document describes SIM800C hardware interface in great detail. The document can help customer to
quickly understand SIM800C interface specifications, electrical and mechanical details. With the help of this
document and other SIM800C application notes, customer guide, customers can use SIM800C to design various
applications quickly.
2. SIM800C Overview
SIM800C is a quad-band GSM/GPRS module that works on frequencies GSM850MHz, EGSM900MHz,
DCS1800MHz and PCS1900MHz. SIM800C features GPRS multi-slot class 12/class10 (optional) and supports
the GPRS coding schemes CS-1, CS-2, CS-3 and CS-4.
With a tiny configuration of 17.6*15.7*2.3mm, SIM800C can meet almost all the space requirements in
customer applications, such as smart phone, PDA and other mobile devices.
SIM800C is a SMT package with 42 pads, and provides all hardware interfaces between the module and
customers’ boards.
One serial port and one full modem serial port;
One USB, the USB interface can debug, download software;
One audio channel which include a microphone input and a speaker output;
Programmable general purpose input and output;
One SIM card interface.
SIM800C is designed with power saving technique so that the current consumption is as low as 0.7mA in sleep
mode.
2.1. SIM800C
Table 1: Module information
SIM800C
GSM
850,900,1800 and 1900MHz
BT
Option
FLASH
24Mbit
RAM
32Mbit
2.2. SIM800C Key Features
Table 2: SIM800C key features
Feature
Implementation
Power supply
3.4V ~4.4V
Power saving
Typical power consumption in sleep mode is 0.7mA (AT+CFUN=0 )
Frequency bands
Quad-band: GSM 850, EGSM 900, DCS 1800, PCS 1900. SIM800C can
search the 4 frequency bands automatically. The frequency bands can also be
set by AT command “AT+CBAND”. For details, please refer to document [1].

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Compliant to GSM Phase 2/2+
Transmitting power
Class 4 (2W) at GSM 850 and EGSM 900
Class 1 (1W) at DCS 1800 and PCS 1900
GPRS connectivity
GPRS multi-slot class 12（default）
GPRS multi-slot class 1~12 (option)
Temperature range
Normal operation: -40°C ~ +85°C
Storage temperature -45°C ~ +90°C
Data GPRS
GPRS data downlink transfer: max. 85.6 kbps
GPRS data uplink transfer: max. 85.6 kbps
Coding scheme: CS-1, CS-2, CS-3 and CS-4
PAP protocol for PPP connect
Integrate the TCP/IP protocol.
Support Packet Broadcast Control Channel (PBCCH)
CSD transmission rates：2.4, 4.8, 9.6, 14.4 kbps
CSD
Support CSD transmission
USSD
Unstructured Supplementary Services Data (USSD) support
SMS
MT, MO, CB, Text and PDU mode
SMS storage: SIM card
SIM interface
Support SIM card: 1.8V, 3V
External antenna
Antenna pad
Audio features
Speech codec modes:
Half Rate (ETS 06.20)
Full Rate (ETS 06.10)
Enhanced Full Rate (ETS 06.50 / 06.60 / 06.80)
Adaptive multi rate (AMR)
Echo Cancellation
Noise Suppression
Serial port and
debug port
Serial port:
Default one Full modem serial port
1200bps to 460800bps
Can be used for AT commands or data stream
Support RTS/CTS hardware handshake and software ON/OFF flow control
Multiplex ability according to GSM 07.10 Multiplexer Protocol
Autobauding supports baud rate from 1200 bps to 115200bps
upgrading firmware
Debug port:
USB_DN and USB_DP
Can be used for debugging and upgrading firmware
Phonebook management
Support phonebook types: SM, FD, LD, RC, ON, MC
SIM application toolkit
GSM 11.14 Release 99
Physical characteristics
Size:17.6*15.7*2.3mm
Weight:1.3g
Firmware upgrade
Main serial port or USB port.(recommend to use USB port)
Table 3: Coding schemes and maximum net data rates over air interface

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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
2.3. Operating Mode
The table below summarizes the various operating modes of SIM800C.
Table 4: Overview of operating modes
Mode
Function
Normal
operation
GSM/GPRS
SLEEP
Module will automatically go into sleep mode if the conditions of sleep
mode are enabling 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.
GSM
IDLE
Software is active. Module is registered to the GSM network, and the
module is ready to communicate.
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 consumption 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 power down by sending AT command “AT+CPOWD=1”or using the PWRKEY.
The power management unit shuts down the power supply for the baseband part of the
module. Software is not active. The serial port is not accessible. Power supply (connected to
VBAT) remains applied.
Minimum
functionality
mode
AT command “AT+CFUN”can be used to set the module to a minimum functionality mode
without removing the power supply. In this mode, 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 mode is lower than normal
mode.
2.4. Functional Diagram
The following figure shows a functional diagram of SIM800C:
GSM baseband
GSM RF

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Antenna interface
Other interface
Analog base
band
Digital base
band
Power management unit
Radio
Frequency
Power
Supply
Analog Interface Digital Interface
UART
SIM
Audio
ADC
RF
USB
GPIO
BT
Figure 1: SIM800C functional diagram

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3. Package Information
3.1. Pin Out Diagram
UART1_DTR
USB_DP
VBAT
VBAT
ADC
UART1_RXD
PWRKEY
UART1_CTS
UART1_TXD
UART1_RTS
UART1_DCD
NETLIGHT
SIM_RSTSIM_CLK
SIM_DET SIM_DATA BT_ANT
UART2_TXD
SPKP
VRTC
MICP
MICN USB_VBUS
USB_DM
GSM_ANT
STATUS
SIM_VDD
UART2_RXD
GND
13
SPKN
UART1_RI
14 15 16 2117 18 19 20
22
23
24
25
26
27
28
29
30
31
32
33
37 36 35 34
1
42 41 40 39 38
5
4
2
3
6
11
10
9
8
7
12
VDD_EXT
GND
GND
GND
GND
GND
GND
GND
UART1_DTR
RF_SYNC
GND
GND
SIM800C
TOP VIEW
Figure 2: Pin assignment (Top view)

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3.2. Pin Description
Table 5: Pin description
Pin name
Pin number
I/O
Description
Comment
Power supply
VBAT
34,35
I
Power supply
VDD_EXT
40
O
2.8V power output
If these pins are unused,
keep open.
GND
8,13,19,21,27,30,
31,33,36,37
Ground
GND for VBAT recommend
to use 36,37pin
Power on/down
PWRKEY
39
I
PWRKEY should be pulled low at
least 1 second and then released to
power on/down the module.
Internally pulled up to
VBAT.
Audio interfaces
MICP
9
I
Differential audio input
If these pins are unused,
keep open.
MICN
10
SPKP
11
O
Differential audio output
SPKN
12
GPIO
NETLIGHT
41
O
Network status
STATUS
42
O
Power on status
Serial port
UART1_DTR
6
I
Data terminal ready
If these pins are unused,
keep open.
UART1_RI
7
O
Ring indicator
UART1_DCD
5
O
Data carrier detect
UART1_CTS
4
O
Request to send
UART1_RTS
3
I
Clear to send
UART1_TXD
1
O
Transmit data
UART1_RXD
2
I
Receive data
UART2_TXD
22
O
Transmit data
UART2_RXD
23
I
Receive data
Debug interface
USB_VBUS
24
I
Debug and download
If these pins are unused,
keep open.
USB_DP
25
I/O
USB_DN
26
I/O
ADC
ADC
38
I
10bit general analog to digital
converter
If these pins are unused,
keep open.
SIM card interface
SIM_VDD
18
O
Voltage supply for SIM card.
Support 1.8V or 3V SIM card
All signals of SIM interface
should be protected against

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SIM_DATA
15
I/O
SIM data input/output
ESD with a TVS diode
array.
SIM_CLK
16
O
SIM clock
SIM_RST
17
O
SIM reset
SIM_DET
14
I
SIM card detection
If these pins are unused,
keep open.
Antenna interface
GSM_ANT
32
I/O
Connect GSM antenna
BT_ANT
20
I/O
Connect Bluetooth antenna
Option, require sw supports
Synchronizing signal of RF
RF_SYNC
29
O
Synchronizing signal of RF
3.3. Package Dimensions
Figure 3: Dimensions of SIM800C (Unit: mm)

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Figure 4: Recommended PCB footprint outline (Unit: mm)

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4. Application Interface
4.1. Power Supply
The power supply range of SIM800C is from 3.4V to 4.4V. Recommended voltage is 4.0V. The transmitting
burst will cause voltage drop and the power supply must be able to provide sufficient current up to 2A. For the
VBAT input, a bypass capacitor (low ESR) such as a 100 µF is strongly recommended.
For the VBAT input, a 100uF Tantalum capacitor (CAlow ESR) and a 1uF~10uF Ceramics capacitor CBare
strongly recommended. Increase the 33pF and 10pF capacitors can effectively eliminate the high frequency
interference. A 5.1V/500mW Zener diode is strongly recommended, the diode can prevent chip from damaging
by the voltage surge. These capacitors and Zener diode should be placed as close as possible to SIM800C
VBAT pins.
VBAT
5.1V
500mW
CACB33pF 10pF
Figure 5: Reference circuit of the VBAT input
Table 6: Recommended zener diode
Vendor
Part number
Power(watts)
Packages
1
On semi
MMSZ5231BT1G
500mW
SOD123
2
Prisemi
PZ3D4V2H
500mW
SOD323
3
Vishay
MMSZ4689-V
500mW
SOD123
4
Crownpo
CDZ55C5V1SM
500mW
0805
The following figure is the reference design of +5V input power supply. The output power supply is 4.1V, thus a
linear regulator can be used.
Vin Vout
GND
FB
3
+
PWR_CTRL
R102
R101
VBAT
100K
43K
+C103
330uF
C104
100nF
U101 MIC29302
5
4
1
2
C101 C102
100uF 1uF
DC INPUT
R103
470R
On/Off
Figure 6: Reference circuit of the LDO power supply

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If there is a high drop-out between the input and the desired output (VBAT), a DC-DC power supply will be
preferable because of its better efficiency especially with the 2A peak current in burst mode of the module. The
following figure is the reference circuit.
FUSE Vin Vout
FB
U101
12
3
4
5
LM2596-ADJ
+
100uH
MBR360
L101
C101 +C102 D102 C103
R102
R101
FB101
330uF
VBAT
2.2K
1K
100uF 1uF
C104
100nF
270
DC INPUT
PWR_CTRL
GND
Ω
On/Off
Figure 7: Reference circuit of the DC-DC power supply
The single 3.7V Li-ion cell battery can be connected to SIM800C VBAT pins directly. But the Ni-Cd or Ni-MH
battery must be used carefully, since their maximum voltage can rise over the absolute maximum voltage of the
module and damage it.
When battery is used, the total impedance between battery and VBAT pins should be less than 150mΩ.
The following figure shows the VBAT voltage drop at the maximum power transmit phase, and the test condition
is as following:
VBAT=4.0V,
A VBAT bypass capacitor CA=100µF tantalum capacitor (ESR=0.7Ω),
Another VBAT bypass capacitor CB=1µF.
577us 4.615ms
Burst:2A
IVBAT
VBAT
Max:350mV
Figure 8: VBAT voltage drop during transmit burst
4.1.1. Power Supply Pin
Pin34 and Pin35 are VBAT input, Pin36 and Pin37 are GND of power supply, VRTC pin is power supply of the
RTC circuit in the module. VDD_EXT output 2.8V when module is in normal operation mode.
When designing the power supply in customer’s application, pay special attention to power losses. Ensure that
the input voltage never drops below 3.0V even when current consumption rises to 2A in the transmit burst. If the
power voltage drops below 3.0V, the module may be shut down automatically. The PCB traces from the VBAT
pins to the power supply must be wide enough (at least 60mil) to decrease voltage drops in the transmit burst.
The power IC and the bypass capacitor should be placed to the module as close as possible.

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SIM800C_Hardware_Design_V1.00 19 2014-10-30
VBAT
MIN:3.0V
Figure 9: The minimal VBAT voltage requirement at VBAT drop
Note: Hardware power down voltage is 3.0V.
4.1.2. Monitoring Power Supply
AT command “AT+CBC”can be used to monitor the VBAT voltage. For detail, please refer to document [1].
4.2. Power on/down Scenarios
4.2.1. Power on SIM800C
Customer can power on SIM800C by pulling down the PWRKEY pin for at least 1 second and release. This pin
is already pulled up to VBAT in the module internal, so external pull up is not necessary. Reference circuit is
shown as below.
4.7K
47K
Turn on/off
impulse
PWRKEY Power
on/down logic
R
VBAT
Module
1K
Figure 10: Powered on/down module using transistor
PWRKEY Power
on/down logic
R
VBAT
Module
1K
Figure 11: Powered on/down module using button
The power on timing is illustrated as in the following figure.

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SIM800C_Hardware_Design_V1.00 20 2014-10-30
VIL<0.7V
Undefind Active
1.2s
VBAT
PWRKEY
(INPUT)
t>3s
VDD_EXT
STATUS
t>1s
Serial port
T>1.4s
Figure 12: Timing of power on module
When power on procedure is completed, SIM800C will send following URC to indicate that the module is ready
to operate at fixed baud rate.
RDY
This URC does not appear when autobauding function is active.
Note: Customer can use AT command “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 port every time when SIM800C is powered on. For details, please refer to the chapter
“AT+IPR”in document [1].
4.2.2. Power down SIM800C
SIM800C will be powered down in the following situations：
Normal power down procedure: power down SIM800C by the PWRKEY pin.
Normal power down procedure: power down SIM800C byAT command “AT+CPOWD=1”.
Abnormal power down: over-voltage or under-voltage automatic power down.
Abnormal power down: over-temperature or under-temperature automatic power down.
4.2.2.1. Power down SIM800C by the PWRKEY Pin
Customer can power down SIM800C by pulling down the PWRKEY pin for at least 1 second and release. Please
refer to the power on circuit. The power down timing is illustrated in the following figure.