Neoway Neo_M660A User Manual

Neo_M660A GPRS Module

Hardware User Guide

Version 1.1

Neo_M660A GPRS Module Hardware User Guide

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No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Shenzhen Neoway Technology Co., Ltd.

is the trademark of Neoway Technology Co., Ltd.

All other trademarks and trade names mentioned in this document are the property of their respective holders.

Notice

This document is intended for system engineers (SEs), development engineers, and test engineers. The information in this document is subject to change without notice due to product version update or

other reasons. Every effort has been made in preparation of this document to ensure accuracy of the contents, but all

statements, information, and recommendations in this document do not constitute a warranty of any kind, express or implied.

Neoway provides customers complete technical support. If you have any question, please contact your account manager or email to the following email addresses:

Sales@neoway.com.cn Support@neoway.com.cn

Website: http://www.neoway.com.cn

Neo_M660A GPRS Module Hardware User Guide

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Revision Record

Issue

Changes

Revised By

Date

V1.0

Initial draft

Li Zhongqiu

2014-06

V1.1

Modified the definition of pin 53

Li Zhongqiu

2014-06

Neo_M660A GPRS Module Hardware User Guide

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Contents

About This Document ......................................................................................................... 1

1 Introduction to M660A ..................................................................................................... 1

1.1 Overview ..................................................................................................................................... 1

1.2 Block Diagram ............................................................................................................................ 1

1.3 Specifications .............................................................................................................................. 2

2 Pin Description and PCB Foot Print .............................................................................. 4

2.1 Specifications and Encapsulation ................................................................................................ 4

2.2 Pin Definition .............................................................................................................................. 5

2.3 PCB Foot Print ............................................................................................................................ 8

3 Interface Design................................................................................................................. 9

3.1 Power Supply and Switch Interfaces ........................................................................................... 9

3.1.1 VBAT ................................................................................................................................. 9

3.1.2 VDD_EXT ....................................................................................................................... 12

3.1.3 VRTC ............................................................................................................................... 12

3.1.4 Power On/Off Procedure .................................................................................................. 13

3.1.5 RESET .............................................................................................................................. 15

3.2 UART ........................................................................................................................................ 16

3.3 USB Interfaces .......................................................................................................................... 18

3.4 DTR and RING ......................................................................................................................... 19

3.4.1 DTR Pin ........................................................................................................................... 19

3.4.2 RING Signal Indicator...................................................................................................... 19

3.5 SIM Card Interface .................................................................................................................... 20

3.6 Running LED Indicator ............................................................................................................. 22

3.7 Audio Interface .......................................................................................................................... 23

3.8 RF Interface ............................................................................................................................... 25

3.8.1 RF Design and PCB Layout ............................................................................................. 25

3.8.2 Recommended RF Connection ......................................................................................... 26

4 Electric Features and Reliability................................................................................... 27

4.1 Electric Feature ......................................................................................................................... 27

4.2 Temperature ............................................................................................................................... 27

4.3 Current....................................................................................................................................... 28

4.4 ESD Protection .......................................................................................................................... 28

5 RF Features ....................................................................................................................... 30

5.1 Work Band ................................................................................................................................. 30

5.1.2 Transmitting Power .......................................................................................................... 30

5.1.3 Receiving Sensitivity ........................................................................................................ 31

6 Mounting the Module onto the Application Board.................................................. 32

7 Package .............................................................................................................................. 32

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8 Abbreviations ................................................................................................................... 33

Neo_M660A GPRS Module Hardware User Guide

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Table of Figures

Figure 2-1 Top view of the M660A module ............................................................................................ 4

Figure 2-2 PCB foot print recommended for M660A (unit: mm) ........................................................... 8

Figure 3-1 Current peaks and voltage drops ............................................................................................ 9

Figure 3-2 Reference design d for the power supply ............................................................................. 10

Figure 3-3 Reference design of power supply control ........................................................................... 10

Figure 3-4 Reference design of power supply controlled by p-MOSFET ..............................................11

Figure 3-5 Reference designs of separated power supply ...................................................................... 12

Figure 3-6 VRTC reference design ........................................................................................................ 13

Figure 3-7 Turning on procedure ........................................................................................................... 13

Figure 3-8 Turning off procedure .......................................................................................................... 14

Figure 3-9 Reference circuit for ON/OFF controlled by low level ........................................................ 14

Figure 3-10 Reference circuit for power-on controlled by high level .................................................... 15

Figure 3-11 Reset circuit with triode separating .................................................................................... 15

Figure 3-12 Signal connection between DCE and DTE ........................................................................ 16

Figure 3-13 Recommended communication circuit between 3.3V MCU and UART ........................... 17

Figure 3-14 Recommended communication circuit between 5V MCU and UART .............................. 17

Figure 3-15 USB circuit ........................................................................................................................ 18

Figure 3-16 RING indicator for incoming call ...................................................................................... 20

Figure 3-17 RING indicator for SMS .................................................................................................... 20

Figure 3-18 Reference design of SIM card interface ............................................................................. 21

Figure 3-19 Reference of SIM card socket ............................................................................................ 21

Figure 3-20 LED indicator directly driven by high level ....................................................................... 22

Figure 3-21 LED indicator driven by transistor ..................................................................................... 22

Figure 3-22 Reference design of MIC differential connections ............................................................. 23

Figure 3-23 Reference design for common audio input ........................................................................ 24

Figure 3-24 Reference design for receiver output ................................................................................. 24

Figure 3-25 Coupling capacitor interfacing ................................ ........................................................... 25

Figure 3-26 Reference design for antenna interface .............................................................................. 25

Figure 3-27 RF layout reference ............................................................................................................ 26

Figure 3-28 Encapsulation specifications of Murata RF connector ....................................................... 26

Figure 3-29 RF connections................................................................................................................... 26

Neo_M660A GPRS Module Hardware User Guide

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Table of Tables

Table 1-1 M660A specifications .............................................................................................................. 2

Table 2-1 M660A pin definition .............................................................................................................. 5

Table 3-1 Power supply and switch interface .......................................................................................... 9

Table 3-2 UART .................................................................................................................................... 16

Table 3-3 USB interface ........................................................................................................................ 18

Table 3-4 DTR and RING pins .............................................................................................................. 19

Table 3-5 SIM card interface ................................................................................................................. 20

Table 3-6 LED indicator ........................................................................................................................ 22

Table 3-7 Audio interface ...................................................................................................................... 23

Table 4-1 Electric feature of the module ............................................................................................... 27

Table 4-2 Temperature Feature ................................................................................................ .............. 27

Table 4-3 Current feature ....................................................................................................................... 28

Table 4-4 ESD feature of the module .................................................................................................... 29

Table 5-1 Work band ............................................................................................................................. 30

Table 5-2 Transmitting power (GSM850&EGSM900) ......................................................................... 30

Table 5-3 Transmitting power (DCS1800&PCS1900) .......................................................................... 30

Neo_M660A GPRS Module Hardware User Guide

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About This Document

This document defines the features, indicators, and test standards of the M660A module and provides reference for the hardware design of each interface. With Neo_M660A GPRS Module AT Command Set, this user guide can help you complete wireless communication application easily.

1 Introduction to M660A

M660A is a compact wireless GSM/GPRS module that supports downlink EDGE. It can provide functions of high-quality voice, SMS, and data services and is widely used in industrial and consumer fields.

1.1 Overview

Neoway M660A module adopts 68-pin LCC encapsulation and its dimensions are 24 mm x 24 mm x 2.6 mm, which can meet most customers' requirements. It provides customers the following hardware resources and features:

 UART interfaces, used for data communication, firmware updating and commissioning, and

supporting hardware flow control

 Audio interfaces, including one line of MIC input (differential) and one line of receiver output

(differential)

 10-bit ADC input, voltage ranging from 0 V to 2.8 V  One line of SIM card interface, compatible with 1.8 V and 3.0V SIM card  RING/LIGHT/DTR (sleep mode) functions  Time updating and timing power-on/off  Firmware updating via USB interface

1.2 Block Diagram

The M660A module consists of baseband controller, Flash ROM, RF section, application interfaces, etc. All sections coordinate with each other to provide such communication functions as GPRS data and voice.

The following figure shows the block diagram of M660A.

Neo_M660A GPRS Module Hardware User Guide

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VBAT

VRTC

Digital

Interface

USB

SIM

UART

ON/OFF

Power

Manager

RF transceiver

FLASH

Digital

Baseband

Analog

Baseband

26 MHz CrystalRF Front-end-module

Audio

Interface

MIC

SIM

PC

ADC

REC

1.3 Specifications

Table 1-1 M660A specifications

Specifications

Description

Band

GSM850/EGSM900/DCS1800/PCS1900 MHz dual-band/quad-band Supporting band locking

Sensitivity

< -107 dBm

Max. transmit power



GSM850/EGSM900 Class4(2W)



DCS1800/PCS1900 Class1(1W)

Protocol

Supporting GSM/GPRS Phase 2/2+

AT  GSM07.07



Extended AT commands

Audio

Supporting the following audio coding:



HR



FR



EFR



AMR

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Supporting echo suppression Supporting recording and DTMF check function

SMS  TEXT/PDU



Supporting SMS message receiving and sending and ring for new SMS messages



Supporting SMS message management: reading/deleting/storage/list

GPRS feature



GPRS CLASS 12



Max. theoretic uplink rate: 85.6 Kbit/s



Max. theoretic downlink rate: 85.6 Kbit/s



Built-in TCP/IP protocol, supporting multiple links



Supporting server and client modes

Circuit Switch Data



CSD



USSD

Supplementary service



Call forwarding



Call waiting



Call holding and multi-way calling

UART



Supporting hardware flow control, RTS and CTS controlled via AT commands



Supporting multiplexing



Supporting AT sending, data transmission, and software download



Supporting baudrate from 1200 bit/s to 115200 bit/s

RTC



Supporting real-time clock and time updating



Supporting timing power-on/off

CPU

ARM7-EJ@360MHz

Antenna feature

50 Ω impedance

Operating temperature

-40℃ to +85℃ Operating voltage

3.5 V to 4.3 V (3.9 V is recommended)

Peak current

Max 2.0 A

Idle current

18 mA

Current in sleep mode

< 2 mA (live network)

< 1 mA (instrument, DRX=9)

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2 Pin Description and PCB Foot Print

2.1 Specifications and Encapsulation

Specifications

M660A

Dimensions

24 mm x 24 mm x 2.6 mm (H x W x D)

Weight

2.6 g

Encapsulation

68-pin LGA

Figure 2-1 Top view of the M660A module

M660A

（TOP VIEW）

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16 17

34

33

32

31

30

29

28

27

26

25

24

23

22

21

20

19

18

51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

ON/OFF

GND

DTR

RING

NC

NC CTS RTS

UTXD

URXD

NC

VDD_EXT

RESET

GND

NC

SIM_RST

SIM_CLK

SIM_DATA

VSIM

GND

USB_DM

USB_DP

VRTC

ADC_IN

VBUS

NC

RECN

RECP

MICN

MICP

GND

NC NC NC NC NC GND GND NC NC NC NC NC GND NC NC NC NC

LIGHT

NC

GND

VBTA

VBAT

GND

GPRS_ANT

GND

NC

11

USB

NC

POWER GND

SIM

UART

AUDIO ADC ANT OTHERS

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2.2 Pin Definition

Table 2-1 M660A pin definition

Name

I/O

Function

Reset

Status

Level Feature

(V)

Remarks

Power Supply and Switch Interfaces

55, 56, 57

VBAT

P

Main power supply input

3.5 V to 4.3 V (3.9 V is recommended)

15

VDD_EXT

P

2.8 V power supply output

Supply power for IO level shifting circuit. Load capability: less than 50 mA

26

VRTC

P

RTC power supply

2.8 V, maximum output charging current 2 mA

2, 17, 18, 29, 39, 45, 46, 53, 54, 58, 59, 61-65

GND

P

Ground 1

ON/OFF

DI

ON/OFF control input

I/PU

0<VIL<0.6

2.1<VIH<VBAT

Low level pulse can change the ON/OFF state.

16

RESET

DI

Reset input

Internal 2.8V pull-up

Low level reset

Audio Interface

19

MICP

AI

Positive electrode of differential MIC output

Vpp≤200 mV 20

MICN

AI

Negative electrode of differential MIC output

21

RECP

AO

Positive electrode of differential receiver output

32 Ω receiver

driving output 22

RECN

AO

Negative electrode of differential receiver output

UART Interface

Neo_M660A GPRS Module Hardware User Guide

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7

CTS

DI

Clear to send

I/PU

0<VIL<0.6

2.1<VIH<3.1 0<VOL<0.42

2.38<VOH<2.8

With internal 47K resistors to respectively pull CTS and URXD up to 2.8 V

8

RTS

DO

Request to send

I/PU

9

UTXD

DO

UART data transmit

O/PU

10

URXD

DI

UART data receive

I/PU

SIM Card

30

VSIM

P

SIM card power supply output

0<VIL<0.25*VSI M

0.75*VSIM<V

IH

<VSIM 0<VOL<0.15*VS

IM

0.85*VSIM<V

OH

<VSIM

Compatible with

1.8/3.0 V SIM card

31

SIM_DATA

DI/O

SIM card data I/O

0<VIL<0.6

2.1<VIH<3.1 0<VOL<0.42

2.38<VOH<2.8

33

SIM_CLK

DO

SIM card clock output

32

SIM_RST

DO

SIM card reset output

LED Indicators

52

LIGHT

DO

Status LED

I/PD

2.8 V/4 mA output

Sleep Mode Controlling

3

DTR

DI

Sleep mode controlling input

I/PD

0<VIL<0.6

2.1<VIH<3.1 0<VOL<0.42

2.38<VOH<2.8

Low level by default

Used together with AT commands

SMS and Incoming Call Ring

4

RING

DO

Ring output

I/PD

0<VIL<0.6

2.1<VIH<3.1 0<VOL<0.42

2.38<VOH<2.8

Detect incoming SMS messages or calls

ADC Detecting

25

ADC_IN

AI

10-bit ADC input

Detectable voltage range: 0 V to 2.8 V

GPRS Antenna

60

GPRS_ANT

AI/O

GPRS antenna interface I/O

50 Ω impedance

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USB Interfaces

24

VBUS

AI

USB voltage test

27

USB_DP

DI/O

USB interface differential data cable

Complying with the USB1.1 standard

Used for firmware download

28

USB_DM

DI/O

Reserved Pins

5, 6, 11~14, 23, 34~38, 40~44, 47~51, 66~68

NC

Must be left disconnected.

Cannot connect to power supply or ground.

P: indicates power supply pins NC: indicates pins that are not supported and must not be connected DI: indicates digital signal input pins DO: indicates digital signal output pins I/PD: indicates digital signal input pins with pull-down I/PU: indicates digital signal input pins with pull-up AI: indicates analogy signal input pins AO: indicates analogy signal output pins

The maximum input voltage at all IO ports (including peak signal current) cannot exceed 3.1 V because the module uses a 2.8 V IO power system. In the application of the module, the IO output voltage from the

3.3 V power supply system of the external circuit might greatly overshoot 3.1 V due to the signal integrity design. In this situation, the IO pins of the module might be damaged if the IO signals are connected to the IO port on the 2.8-V system. To rectify this issue, take measures to match the level. For details, see the 3.2 UART.

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2.3 PCB Foot Print

LCC packaging is adopted to package the pins of the M660A module. Figure 2-2 shows the recommended PCB foot print.

Figure 2-2 PCB foot print recommended for M660A (unit: mm)

1.004.00

4.00

24.00

12.00

3.78

4.97

1.60

0.60

4.4

4.

4

2.4

1.30

3.03

Keepout Area A

Keepout Area B



No trace or copper is allowed in the keepout aera.

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3 Interface Design

3.1 Power Supply and Switch Interfaces

Table 3-1 Power supply and switch interface

Pin Name

I/O

Function

Remarks

VBAT

P

Main power supply input

3.5 V to 4.3 V (3.9 V is recommended)

VDD_EXT

P

2.8 V power supply output

Loading capability < 50 mA

VRTC

P

RTC power supply input

2.8 V, 2 mA at most

ON/OFF

DI

ON/OFF input

Triggered by low level

RESET

DI

Module reset input

Triggered by low level Keep more than 100 ms

3.1.1 VBAT

VBAT is the main power supply of the module. Its input voltage ranges from 3.5 V to 4.3 V and the preferable value is 3.9V. In addition to digital signals and analog signals, it supplies power for RF power

amplifier. The performance of VBAT is a critical path to module's performance and stability. The peak input current at

the VBAT pin can be up to 2 A when the signal is weak and the module works at the maximum transmitting power. The voltage will encounter a drop in such a situation. If the voltage drops lower than 3.5 V, the module might restart.

Figure 3-1 Current peaks and voltage drops

Keep above 3.5 V

3.5 V

0 ms

3.7 ms 7.4 ms 10.7 ms

T

2 A

Voltage

Input

current

3.9 V

Neo_M660A GPRS Module Hardware User Guide

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Figure 3-2 shows a recommended power supply design for the module.

Figure 3-2 Reference design d for the power supply

Power Supply GPRS Module

Close to the pin of the module

D1

C1 C2 C3 C4

VBAT

Current testing point

I_max

C5

In the circuit, you can use TVS at D1 to enhance the performance of the module during a burst. SMF5.0AG (Vrwm=5V&Pppm=200W) is recommended. A large bypass tantalum capacitor (220 μF or 100 μF) or aluminum capacitor (470 μF or 1000 μF) is expected at C1 to reduce voltage drops during bursts together with C2 (10 μF capacitor). In addition, you need to add 0.1 μF, 100 pF, and 33 pF filter capacitors to enhance the stability of the power supply.

A controllable power supply is preferable if used in harsh conditions. The module might fail to reset in remote or unattended applications, or in an environment with great electromagnetic interference (EMI). If you adapt 5 V power supply, you can use the EN pin on the LDO or DC/DC chipset to control the switch of the power supply as shown in Figure 3-3.

MIC29302WU in the following figure is an LDO, which can output 3 A current.

Figure 3-3 Reference design of power supply control

VCC_IN_5V

GPRS_EN

VBAT

100 uF

TAN

0.1 uF

TVS

5V

0.1 uF

470 uF

TAN

EN

VIN

VOUT

ADJ

MIC29302WU

10K

4.75K

2

1

6

4

5

3

The alternative way is to use a p-MOSFET to control the module's power supply, as shown in Figure 3-4. When the external MCU detects the exceptions such as no response from the module or the disconnection of GPRS, power off/on can rectify the module exceptions.

Neo_M660A GPRS Module Hardware User Guide

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Figure 3-4 Reference design of power supply controlled by p-MOSFET

VCC_IN_3.9V

VBAT

10K

100K

33 pF

10 uF

GPRS_EN

2K

10K

0.1 uF

Q1

R4

C1

C2

C4

C5

C7

R1

R2

10 uF 0.1 uF

R3

Q2

TVS

5V

470 uF

C3

C6

100pF

S

G

D

In Figure 3-4, the module is powered on when GPRS_EN is set to high level. Q2 is added to eliminate the need for a high enough voltage level of the host GPIO. In case that the GPIO

can output a high voltage greater than VCC_IN_3.9V - |V

GS(th)

|, where V

GS(th)

is the Gate Threshold Voltage,

Q2 is not needed. Reference components:



Q1 can be IRML6401 or Rds(on) p-MOSFET which has higher withstand voltage and drain current.



Q2: a common NPN transistor, e.g. MMBT3904; or a digital NPN transistor, e.g. DTC123. If digital transistor is used, delete R1 and R2.



C3: 470 μF tantalum capacitor rated at 6.3 V; or 1000 μF aluminum capacitor. If lithium battery is used to supply power, C3 can be 220 μF tantalum capacitor.

Protection

Place a TVS diode (V

RWM

=5 V) on the VBAT power supply to ground, especially in automobile applications. For some stable power supplies, zener diodes can decrease the power supply overshoot. MMSZ5231B1T1G from ONSEMI and PZ3D4V2 from Prisemi are options.

Trace

The trace width of primary loop lines for VBAT on PCB must be able to support the safe transmission of 2A current and ensure no obvious loop voltage decrease. Therefore, the trace width of VBAT loop line is required at least 2 mm and the ground should be as complete as possible.

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Separating

As shown in Figure 3-1, the GPRS module works in burst mode that generates voltage drops on power supply. And furthermore this results in a 217 Hz TDD noise through power (One of the way generating noise. Another way is through RF radiation). Analog parts, especially the audio circuits, are subjected to this noise, known as a "buzz noise" in GSM systems. To prevent other parts from being affected, it's better to use separated power supplies. The module shall be supplied by an independent power, like a DC/DC or LDO. See Figure 3-5.

DC/DC or LDO should output rated peak current larger than 2 A. The inductor used in Reference Design (b) should be a power inductor and have a very low resistance. 10

μH with average current ability greater than 1.2 A and low DC resistance is recommended.

Figure 3-5 Reference designs of separated power supply

Other circuit

DC-DC/LDO

GPRS

module

DC-DC/LDO

Power

Input

Other circuitDC-DC/LDO

GPRS

module

Power

Input

10 uH

Reference Design (a) Reference Design (b)

EMC Considerations

Place transient overvoltage protection components like TVS diode on power supply, to absorb the power surges. SMAJ5.0A/C could be a choice.

Never use a diode to make the drop voltage between a higher input and module power. Otherwise, Neoway will not provide warranty for product issues caused by this. In this situation, the diode will obviously decrease the module performances, or result in unexpected restarts, due to the forward voltage of diode will vary greatly in different temperature and current.

3.1.2 VDD_EXT

It is recommended that VDD_EXT is only used for interface level shifting. VDD_EXT can output 2.8 V and 50 mA. It stops output after the module is shut down.

3.1.3 VRTC

VRTC is the external power supply pin of RTC inside the module. It can be connected to external battery or supercapacitor. When VBAT works properly, VRTC outputs 2.8 V and maximum 2 mA and can be connected to battery or supercapacitor to charge. When VBAT is disconnected, the module can discharge the battery or capacitor to supply power for RTC circuit in short time. Leave this pin disconnected if not used.

0 shows the reference design of the VRTC power supply.

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Figure 3-6 VRTC reference design

Backup

battery

GPRS Module

RTC

Circuit

Capacitor

VRTC

3.1.4 Power On/Off Procedure

Prior to turning on the module, power on the host MCU and finish the UART initialization. Otherwise conflictions may occur during initialization, due to unstable conditions.

ON/OFF is a low level pulse active input, used to turn on or off the module.

Turning on the Module

While the module is off, power on the module, drive the ON/OFF pin to ground for at least 1.2 second and then release. The module starts. After the module is started up, keep the ON/OFF pin at high level. The UART port will send an unsolicited message (MODEM:STARTUP), indicating the powering on of the module and can respond to the AT commands.

When you design your program, you can use the unsolicited message (MODEM:STARTUP) to check whether the module is started or reset improperly.

Figure 3-7 shows the procedure of powering on the module.

Figure 3-7 Turning on procedure

VBAT

ON/OFF

VDD_EXT

UART

1.2s

3s

300 ms

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Turning off the Module

While the module is on, drive the ON/OFF pin to ground for at least 500 ms and then release. The module will detach to network and 2 seconds later it will shut down. Then shut down the main power supply. Figure 3-8 shows the procedure of turning off the module. Another approach to turn off the module is using AT commands. For details, see Neo_M660A GPRS Module AT Command Set.

Figure 3-8 Turning off procedure

VBAT

ON/OFF

VDD_EXT

UART

2 s

500 ms

Figure 3-9 shows a reference circuit for ON/OFF control with inverted control logic.

Figure 3-9 Reference circuit for ON/OFF controlled by low level

GPRS Module

ON/OFF

TVS

S 1

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Figure 3-10 Reference circuit for power-on controlled by high level

USER_ON

GPRS Module

ON/OFF

4.7K

47K

R1

R2

In Figure 3-10, high level takes effect for ON/OFF on the user side (USER_ON). R1 and R2 can be adjusted according to the driving capability of the USER_ON pin. Use a common NPN transistor, e.g. MMBT3904; or a digital NPN transistor, e.g. DTC123. If digital transistor is used, delete R1 and R2.



Level abnormalities at interfaces connected to the external MCU, especially the UART port, might affect the power on procedure of the module. For example, when a module is turned on, the IO ports of the MCU are still in output status because they have not been initialized completely. The module might fails to start if the UTXD signal (output pin) is forced to pull up or down.



The better way to rescue the module from abnormal condition, is to apply a power OFF-ON procedure, rather than using the ON/OFF control signal. In fact ON/OFF signal is software-dependent.

3.1.5 RESET

Pull the RESET signal to low level for more than 100 ms to reset the module. A pull-up resistor is internally included and the typical high level is 2.8 V. The RESET pin can be left disconnected if not used. A triode has been used in the internal RESET circuit. Please refer to Figure 3-11.

Figure 3-11 Reset circuit with triode separating

Reset

Circuit

R1

R2

2.8V

RESET

GPRS Module

Neo_M660A GPRS Module Hardware User Guide

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3.2 UART

Table 3-2 UART

Pin Name

I/O

Function Description

Remarks

RTS

DO

Request to send

CTS

DI

Clear to send

URXD

DI

UART data receive

UTXD

DO

UART data transmit

UART is used for AT commands, data sending/receiving, firmware updating, etc. Figure 3-12 shows the signal connection between the module (DCE) and the terminal (DTE).

Figure 3-12 Signal connection between DCE and DTE

DCE

URXD

UTXD

CTS

RTS

DTE

UTXD

URXD

RTS

CTS

The UART of M660A works at 2.8 V CMOS logic level. The voltages for input high level should not exceed 3.1 V. Supported baud rates range from 300 bit/s to 921600 bit/s and the default rate is 115200 bit/s. For more details about baudrate, see Neo_M660A GPRS Module Hardware User Guide.

If the UART is interfacing with an MCU that has 3.3 V logic levels, resistors should be connected in series with the signals.

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Figure 3-13 Recommended communication circuit between 3.3V MCU and UART

VDD_EXT

0.1 uF

47K

RB521S

200 Ω

33 pF

MCU_UTXD

MCU_URXD

Module_URXD

Module_UTXD

In Figure 3-13, 100 pF filter capacitor should be placed near the receive pin of the module. Resistor (200 Ω to 470 Ω) and capacitor (100 pF to 470 pF) can be selected based on the tested signal wave. Great serial resistance and filter capacity will decrease the signal level significantly, resulting in undesired signal wave distortion and the low adaptable UART communication baudrate. RB521S-30TE-61, RB521SM-30GJT2R, and LRB521S-30T1G are recommended for separating diode.

When the external MCU adopts 5 V IO system, level shifting is required for both UART receive and transmit. Figure 3-14 shows a reference circuit design.

Figure 3-14 Recommended communication circuit between 5V MCU and UART

OUTPUT

VCC_IN VDD_EXT

4.7K 10K

INPUT

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INPUT is connected to TXD of the MCU and VCC_IN is connected to the 5 V power supply of the external MCU. OUTPUT is connected to RXD of the module. If the circuit is far away from the VDD_EXT pin, add a 0.1 μF decoupling capacitor to VDD_EXT.

Level shifting between RXD of the MCU and TXD of the module can be designed in the similar way. The pull-up resistor R3 ranges from 4.7 K to 10 K; R2 ranges from 2 K to 10 K. Resistors are selected based

on the voltage of the power supply and UART baudrate. You can select resistors with great resistance to reduce the power consumption when the power supply has great voltage or the baudrate is low. But, the resistance will affect the quality of the square wave. In addition, the circuit performance is affected by the signal traces during PCB layout.

It is recommended that you choose a high-speed NPN transistor because the Q1 switch rate will affect the wave quality after level shifting. MMBT3904 or MMBT2222 is recommended.

Avoid data produced at UART when the module is turned on. You are advised to send data to the UART 3 seconds after the module is turned on so that the module would not respond wrongly.

3.3 USB Interfaces

Table 3-3 USB interface

Pin Name

I/O

Function

Remarks

VBUS

AI

USB voltage check

4.3 V < VBUS < 7 V, typical value: 5 V

USB_DP

DIO

Positive signal of USB data

USB_DM

DIO

Negative signal of USB data

For M660A modules, you can download firmware through USB interfaces. Before download the firmware, connect the USB interface to a computer and power on the module. A dedicated download tool is required.

Figure 3-15 shows the recommended connection between the module and a computer.

Figure 3-15 USB circuit

GPRS Module

VBUS

USB_DM

USB_DP

GND

PC

UTXD

URXD

RTS

CTS

VBUS

USB_DM

USB_DP

GND

20 Ω

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Parallel a 1 μF filter capacitor on VBUS and place it as close to the pin as possible. You must also add TVS to the VBUS power cable. Use TVS diodes with a capacity of lower than 12 pF for protection on the data cables of USB_DP and USB_DM and adopt Differential Signal trace for USB_DP and USB_DM and ensure complete ground for separation.

USB interface is used only for software download.

3.4 DTR and RING

Table 3-4 DTR and RING pins

Pin Name

I/O

Function

Remarks

DTR

DI

Signal for controlling sleep mode

Low level by default Left disconnected if not used

RING

DO

Ring output

Left disconnected if not used

3.4.1 DTR Pin

Generally DTR is used to control sleep mode together with AT commands. For details, see Neo_M660A GPRS Module AT Command Set. Based on the setting of the selected mode, pulling DTR low will bring the

module into sleep mode if the module is idle. In this mode, the idle current is less than 2 mA, depending on the DRX setting of network.

In sleep mode, the module can respond to the incoming call, SMS, and GPRS data. The host MCU can also control the module to exit sleep mode by controlling DTR.

Process of entering the sleep mode:

1. Keep DTR high level in normal working mode. Activate the sleep mode by using the

AT+ENPWRSAVE=1 command.

2. Pull DTR low, and the module will enter sleep mode, but only after process and pending data

finished.

3. In the sleep mode, the external MCP can pull DTR high so that the module will exit from sleep mode

actively. Then the module can transmit data and initiate calls. After processing is finished, pull DTR low again to take the module back to sleep mode.

4. In sleep mode, the module can be woken up by the events of incoming voice call, received data, or

SMS. Meanwhile the module will send out the unsolicited messages through the UART. Upon receipt of the unsolicited messages, the host MCU should pull DTR high firstly, otherwise the

module will resume sleep mode in two minutes after the service processing. And then the host MCU can process the voice call, received data, or SMS. After processing is finished, pull DTR low again to put the module into sleep mode.

3.4.2 RING Signal Indicator



Calling: Once a voice call is coming, UART output "RING" character strings and meanwhile the RING pin outputs 250 ms low pulses at 4s period. After the call is answered, the high level restores.

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Figure 3-16 RING indicator for incoming call

4 s

250 ms



SMS: Upon receipt of SMS, the module outputs one 600 ms low pulse.

Figure 3-17 RING indicator for SMS

600 ms

3.5 SIM Card Interface

Table 3-5 SIM card interface

Pin Name

I/O

Function Description

Remarks

VSIM

P

SIM card power supply output

1.8/3.0V

SIM_CLK

DO

SIM card clock output

SIM_RST

DO

SIM card reset output

SIM_DATA

DI/O

SIM card data IO

With internal pull-up resistor

M660A supports 3.0 V and 1.8 V SIM cards. VSIM supplies power for SIM card at Max. 30 mA. SIM_DATA is pulled up by an internal resistor. You do not have to add and external pull-up resistor in your

design. SIM_CLK can work at several frequencies at 3.25 MHz typically. SIM card is sensitive to GSM TDD noise

and RF interference. So, the PCB design should meet the following requirements:



The antenna especially build-in antenna should be installed a long distance away from the SIM card and SIM card traces.



The PCB traces of SIM should be as short as possible and shielded with GND copper.

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Figure 3-18 Reference design of SIM card interface

20 Ω

1 uF

SIM_DATA

SIM_CLK

SIM_RST

VSIM

GPRS Module

CLK RST

VCC

GND

SIM Card

DATA

VPP

ESD protectors, such as ESD diodes (lower than 33 pF) or ESD varistors, are recommended on the SIM signals, especially in automotive electronics or other applications with badly ESD. In other applications, replace ESD diodes with 27 pF to 33 pF grounding capacitors. The ESD diodes or small capacitors should be close to the SIM card pin on the socket.

If you use 6-pin SIM card sockets, MCP-C713(H2.8) is recommended. Figure 3-19 shows its encapsulation.

Figure 3-19 Reference of SIM card socket

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3.6 Running LED Indicator

Table 3-6 LED indicator

Pin Name

I/O

Function

Remarks

LIGHT

DO

Indicates running status

2.8 V output, max. 4 mA

When the module is running, the LED indicator is driven by the LIGHT pin to indicate different module status with its various blink behaviors. For how to set the LED indicator, see Neo_M660A GPRS Module AT Command Set.

LIGHT can output 4 mA current and 2.8 V high level, therefore the LED can be directly connected to this pin with a resistor in series. For better luminance, drive the LED with a transistor instead.

Figure 3-20 LED indicator directly driven by high level

LIGHT

GPRS

Module

1K

Figure 3-21 LED indicator driven by transistor

LIGHT

GPRS Module

10K

VCC

470 Ω

4.7K

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3.7 Audio Interface

Table 3-7 Audio interface

Pin Name

I/O

Function

Remarks

MICP

AI

Positive electrode of MIC output

Vpp≤200 mV MICN

AI

Negative electrode of MIC output

RECP

AO

Positive electrode of receiver output

32Ω receiver driving output RECN

AO

Negative electrode of receiver output

M660A supports two lines of audio interfaces. You can switch the audio channels and adjust the volume via AT commands. For details, see Neo_M660A GPRS AT Command Set.

Figure 3-22 shows a reference audio interface design. The peak voltage routed to MICP/MICN should not exceed 200 mV AC. AGC circuit is integrated inside the module. Electret microphone is suited.

The module can meet the requirements of common handsets with AGC and volume control.

Figure 3-22 Reference design of MIC differential connections

GPRS Module

33 pF

MIC

33 pF

100 pF

MICN

MICP

In Figure 3-23, a bias voltage for microphone is provided through MICP and MICN. But if an amplifier is used between the microphone and module, capacitors like C1 and C2, should be placed between the outputs of amplifier and module, to block the bias voltage.

For a peak voltage greater than 200 mV AC, an attenuation circuit comprised of R1-R4 should be used.

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Figure 3-23 Reference design for common audio input

GPRS Module

33 pF

MICN

MICP

MIC_BIAS

Baseband

Circuit

2.2 uF

R6

2.2 KΩ

R5

2.2 kΩ

C1

C2

User's

Circuit

R1

R3

R2

R4

In Figure 3-22 and Figure 3-23, the audio input circuits are designed to meet the requirements for small audio signal, far away from interference source and masking PCB routing by ground.

Figure 3-24 shows a reference design for the receiver interface, which can drive a 32 Ω receiver directly.

Figure 3-24 Reference design for receiver output

GPRS Module

33 pF

Receiver@32Ω

33 pF

100 pF

RECN

RECP

If an external amplifier is used for driving the speakers, coupling capacitors of 2.2 μF to 4.7 μF should be used to block the DC voltage, as shown in Figure 3-25.

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Figure 3-25 Coupling capacitor interfacing

GPRS Module

RECN

RECP

C1

C2

User's

Circuit

3.8 RF Interface

3.8.1 RF Design and PCB Layout

GPRS_ANT is the antenna interface of the module. A 50 Ω antenna is required. VSWR ranges from 1.0 to

1.5. The antenna should be well matched to achieve best performance. It should be installed far away from high speed logic circuits, DC/DC power, or any other strong disturbing sources.

For multiple-layer PCB, the trace between the antenna pad of module and the antenna connector, should

have a 50 Ω characteristic impedance, and be as short as possible. The trace should be surrounded by ground

copper. Place plenty of via holes to connect this ground copper to main ground plane, at the copper edge. If the trace between the module and connector has to be longer than 10 mm, or built-in antenna is used, a

π-type matching circuit should be added, as shown in Figure 3-26. The types and values of C1, L1, and L2 should be verified by testing using network analyzer instrument. If the characteristic impedance is well matched, and VSWR requirement is met, just use a 0 Ω resistor for C1 and leave L1, L2 un-installed.

Avoid any other traces crossing the antenna trace on neighboring layer.

Figure 3-26 Reference design for antenna interface

GPRS Module

ANT

C1

GPRS_ANT

L2

L1

On two-layer boards which cannot control resistance properly, the RF route should be as short (less than 10 mm) and smooth as possible and at a width of 0.5 mm; the RF is 0.5 mm away from the ground.

Figure 3-27 shows a two-layer board application. The RF is connected to GSC RF connector through traces on PCB, which is connected to the antenna via cable.

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Figure 3-27 RF layout reference

The RF traces are wide 0.5 mm; leave space at least 0.5 mm between the coppers. Drill enough grounding holes.

Ensure that the ground pins on both sides of the antenna are grounded completely and they form a complete circle with grounding copper.

ESD protection is built in module. For special ESD protection, an ESD diode can be placed close to the antenna. But ensure using a low junction capacitance ESD diode. The junction capacitance should be less than 0.5 pF, otherwise the RF signal will be attenuated. RCLAMP0521P from Semtech, or ESD5V3U1U from Infineon, can be used here.

On the PCB, keep the RF signals and RF components away from high-speed circuits, power supplies, transformers, great inductors, the clock circuit of single-chip host, etc.

3.8.2 Recommended RF Connection

If you adopts RF cables for connections, the GSC RF connector MM9329-2700RA1 from Murata is recommended. Figure 3-28 shows the encapsulation specifications.

Figure 3-28 Encapsulation specifications of Murata RF connector

RF cable can also be connected to the module by soldering. In this manner, you must ensure proper soldering in case of damage that lowers RF performance. Figure 3-29 shows the pictures of these two connections.

Figure 3-29 RF connections

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4 Electric Features and Reliability

4.1 Electric Feature

Table 4-1 Electric feature of the module

Parameter

Minimum Value

Typical Value

Maximum Value

VBAT Vin

3.5 V

3.9 V

4.3 V

Iin / /

2 A

VBUS

4.3 V

5 V

7 V

VDD_EXT Vout

/

2.8 V

/

Iout / /

50 mA

DIO

Vout

2.3 V

2.8 V

3.1 V

Iout / /

4 mA

Vin

-0.3 V

0 V

0.6 V

Iin / /

22.5 μA

If the voltage is too low, the module might fail to start. If the voltage is too high or there is a voltage burst during the startup, the module might be damaged permanently.

If you use LDO or DC-DC to supply power for the module, ensure that it output at least 2 A current.

4.2 Temperature

Table 4-2 Temperature Feature

Module Status

Minimum Value

Typical Value

Maximum Value

Working

-40℃

25℃

85℃

Storage

-45℃

90℃

If the module works in temperature exceeding the thresholds, its RF performance (e.g. frequency deviation or phase deviation) might be worse but it can still work properly.

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4.3 Current

Table 4-3 Current feature

Parameter

Testing Conditions

Testing Result

(Average Current)

Testing voltage

3.9 V Agilent power supply

/

Idle mode

Set the instrument and power on the module.

18 mA

Off leakage current

Power on the module or use AT command to shut the module down.

60 μA

Average network searching current

Set the instrument. Start the module. Wait until the module registers the

instrument.

60 mA

Sleep mode

On a live network, the module registers the network and then enters the sleep mode.

1.8 mA Set the instrument properly (DRX=9)

992 μA

Voice service

Maximum power level in full rate mode

GSM850

210 mA

EGSM900

200 mA

DCS1800

135 mA

PCS1900

140 mA

GPRS class 12

4TX,1RX(4Up/1Down)

GSM850

425 mA

EGSM900

422 mA

DCS1800

260 mA

PCS1900

275 mA

1TX,4RX(1Up/4Down)

GSM850

200 mA

EGSM900

185 mA

DCS1800

155 mA

PCS1900

140 mA

The data in the above table is typical values obtained during tests in lab. It might be a little bit different caused by the difference of the module hardware. Also, the test results might be various due to different setting or testing methods.

4.4 ESD Protection

Electronics need to pass sever ESD tests. The following table shows the ESD capability of key pins of our module. It is recommended that you add ESD protection to those pins in accordance to the application to ensure your product quality when designing your products.

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Humility: 45% Temperature: 25℃

Table 4-4 ESD feature of the module

Testing Point

Contact Discharge

Air Discharge

VBAT

±8KV

±15KV

GND

±8KV

±15KV

ANT

±8KV

±15KV

Cover

±8KV

±15KV

RXD/TXD

±4KV

±8KV

USB

±4KV

±8KV

MIC/ REC

±4KV

±8KV

Others

±4KV

±8KV

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5 RF Features

5.1 Work Band

Table 5-1 Work band

Work Band

Uplink

Downlink

GSM850

824~849MHz

869~894MHz

EGSM900

880~915MHz

925~960MHz

DCS1800

1710~1785MHz

1805~1880MHz

PCS1900

1850~1910MHz

1930~1990MHz

5.1.2 Transmitting Power

Table 5-2 Transmitting power (GSM850&EGSM900)

PCL

Transmitting Power

Threshold Range

5

33 dBm

±2 dBm

6

31 dBm

±3 dBm

7

29 dBm

±3 dBm

8

27 dBm

±3 dBm

9

25 dBm

±3 dBm

10

23 dBm

±3 dBm

11

21 dBm

±3 dBm

12

19 dBm

±3 dBm

13

17 dBm

±3 dBm

14

15 dBm

±3 dBm

15

13 dBm

±5 dBm

16

11 dBm

±5 dBm

17

9 dBm

±5 dBm

18

7 dBm

±5 dBm

19

5 dBm

±5 dBm

Table 5-3 Transmitting power (DCS1800&PCS1900)

PCL

Transmitting Power

Threshold Range

0

30 dBm

±2 dBm

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1

28 dBm

±3 dBm

2

26 dBm

±3 dBm

3

24 dBm

±3 dBm

4

22 dBm

±3 dBm

5

20 dBm

±3 dBm

6

18 dBm

±3 dBm

7

16 dBm

±3 dBm

8

14 dBm

±3 dBm

9

12 dBm

±3 dBm

10

10 dBm

±4 Bm

11

8 dBm

±4 Bm

12

6 dBm

±4 Bm

13

4 dBm

±4 dBm

14

2 dBm

±5 dBm

15

0 dBm

±5 dBm

5.1.3 Receiving Sensitivity

Band

Typical

GSM800&EGSM900

<-107 dBm

DCS1800&PCS1900

<-107 dBm

The data in the above tables is obtained by connecting the module to RF test instrument (e..g. CMU200, CWM500, or Agilent8960) in lab tests. It is for reference only.

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6 Mounting the Module onto the Application Board

M660A is compatible with industrial standard reflow profile for lead-free SMT process. The reflow profile is process dependent, so the following recommendation is just a start point guideline:



Only one flow is supported.



Quality of the solder joint depends on the solder volume. Minimum of 0.15 mm stencil thickness is recommended.



Use bigger aperture size of the stencil than actual pad size.



Use a low-residue, no-clean type solder paste.

7 Package

M660Amodules are packaged in sealed bags on delivery to guarantee a long shelf life. Package the modules again in case of opening for any reasons.

If exposed in air for more than 48 hours at conditions not worse than 30°C/60% RH, a baking procedure should be done before SMT. Or, if the indication card shows humidity greater than 20%, the baking procedure is also required.

The baking should last for at least 12 hours at 90℃.

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8 Abbreviations

ADC

Analog-Digital Converter

AFC

Automatic Frequency Control

AGC

Automatic Gain Control

AMR

Acknowledged multirate (speech coder)

CSD

Circuit Switched Data

CPU

Central Processing Unit

DAI

Digital Audio interface

DAC

Digital-to-Analog Converter

DCE

Data Communication Equipment

DSP

Digital Signal Processor

DTE

Data Terminal Equipment

DTMF

Dual Tone Multi-Frequency

DTR

Data Terminal Ready

EFR

Enhanced Full Rate

EGSM

Enhanced GSM

EMC

Electromagnetic Compatibility

EMI

Electro Magnetic Interference

ESD

Electronic Static Discharge

ETS

European Telecommunication Standard

FDMA

Frequency Division Multiple Access

FR

Full Rate

GPRS

General Packet Radio Service

GSM

Global Standard for Mobile Communications

HR

Half Rate

IC

Integrated Circuit

IMEI

International Mobile Equipment Identity

LCD

Liquid Crystal Display

LED

Light Emitting Diode

MS

Mobile Station

PCB

Printed Circuit Board

PCS

Personal Communication System

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RAM

Random Access Memory

RF

Radio Frequency

ROM

Read-only Memory

RMS

Root Mean Square

RTC

Real Time Clock

SIM

Subscriber Identification Module

SMS

Short Message Service

SRAM

Static Random Access Memory

TA

Terminal adapter

TDMA

Time Division Multiple Access

UART

Universal asynchronous receiver-transmitter

VSWR

Voltage Standing Wave Ratio

Neoway Neo_M660A User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual