Telit Communications GM862-QUAD Manuale di installazione
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 1 of 69
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Telit Communications S.p.A. 2005
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 2 of 69
Contents
1OVERVIEW 4
2HARDWARE COMMANDS 5
2.1 Turning ON the GM862-QUAD 5
2.2 Turning OFF the GM862-QUAD 7
2.2.1.1 Hardware shutdown 7
2.2.1.2 Hardware Unconditional Reset 7
3POWER SUPPLY 9
3.1 Power Supply Requirements 9
3.2 General Design Rules 9
3.2.1 Electrical design Guidelines 10
3.2.1.1 + 5V input Source Power Supply Design Guidelines 10
3.2.1.2 + 12V input Source Power Supply Design Guidelines 11
3.2.1.3 Battery Source Power Supply Design Guidelines 12
3.2.1.4 Battery Charge control Circuitry Design Guidelines 12
3.2.2 Thermal Design Guidelines 14
3.2.3 Power Supply PCB layout Guidelines 15
4SERIAL PORT 17
4.1 RS232 level translation 19
4.2 5V UART level translation 21
5MICROPHONE 23
5.1 Microphone line Characteristic and requirements 23
5.2 General Design Rules 26
5.3 Microphone Biasing 26
5.3.1 Balanced Microphone biasing 27
5.3.2 Unbalanced Microphone biasing 28
5.4 Microphone buffering 29
5.4.1 Buffered Balanced Mic. 29
5.4.2 Buffered Unbalanced (Single Ended) Mic. 31
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 3 of 69
6SPEAKER 34
6.1 Speaker lines characteristics and requirements 34
6.2 General Design rules 36
6.2.1 Noise Filtering 36
6.3 Handset earphone design 36
6.4 Hands Free earphone (low power) design 38
6.5 Car Kit speakerphone design 38
7GENERAL PURPOSE I/O 40
7.1 Using a GPIO pin as INPUT 40
7.2 Using a GPIO pin as OUTPUT 40
7.3 Using the Alarm Output GPIO6 41
7.4 Using the Buzzer Output GPIO7 41
8CAMERA 42
8.1 Agilent Camera 42
8.1.1 Camera interface connectors 42
8.1.2 EVB for camera support 44
8.2 Camera Transchip 45
8.2.1 Camera interface connectors 45
8.2.2 EVB for Agilent and Transchip camera support 47
8.2.3 Block Diagram for supported cameras 48
8.2.4 Schematic Diagrams for supported cameras 49
8.2.5 Example usage script for camera 51
9DOCUMENT CHANGE LOG 52
10 ANNEX A - EVK SCHEMATICS 53
11 ANNEX B - CAMERA EVB SCHEMATICS 65
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 4 of 69
1 Overview
The aim of this document is the description of some hardware solutions useful for developing a
product with the Telit GM862-QUAD/-QUAD-PY modules.
In this document all the basic functions of a mobile phone will be taken into account; for each one
of them a proper hardware solution will be suggested and eventually the wrong solutions and
common errors to be avoided will be evidenced. Obviously this document can not embrace the
whole hardware solutions and products that may be designed. The wrong solutions to be avoided
shall be considered as mandatory, while the suggested hardware configurations shall not be
considered mandatory, instead the information given shall be used as a guide and a starting point for
properly developing your product with the Telit GM862-QUAD/-QUAD-PY modules. For further
hardware details that may not be explained in this document refer to the GM862-QUAD/-QUAD-
PY Product Description document where all the hardware information is reported.
NOTE: In this document all the hardware solution are referenced to the GM862-QUAD.
As a general rule, since all the product line GM862-QUAD, GM862-QUAD-PY is pin to pin
hardware compatible, all these solutions apply also to the GM862-QUAD-PY.
NOTE
The information presented in this document is believed to be accurate and reliable. However, no responsibility is
assumed by DAI Telecom for its use, nor any infringement of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any patent rights of DAI Telecom other than for
circuitry embodied in Telit products. This document is subject to change without notice.
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 5 of 69
2 Hardware Commands
2.1 Turning ON the GM862-QUAD
To turn on the GM862-QUAD the pin ON# must be tied low for at least 1 second and then released.
The maximum current that can be drained from the ON# pin is 0,1 mA.
A simple circuit to do it is:
NOTE: don't use any pull up resistor on the ON# line, it is internally pulled up. Using pull up resistor
may bring to latch up problems on the GM862-QUAD power regulator and improper power on/off of the
module. The line ON# must be connected only in open collector configuration.
NOTE: In this document all the lines that are inverted, hence have active low signals are labeled with a
name that ends with a "#" or with a bar over the name.
TIP: To check if power has raised it is possible to monitor the START line, when this line goes high the
module is powered on, but before it remains on the device needs other 900 ms for software startup.
Hence check the PWRCTL line and 900 ms after its transition to high it is possible to release the ON#
pin.
ON#
Power ON impulse
GND
R1
R2
Q1
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 6 of 69
For example:
1- Let's assume you need to drive the ON# pin with a totem pole output of a +3/5 V microcontroller
(uP_OUT1):
2- Let's assume you need to drive the ON# pin directly with an ON/OFF button:
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 7 of 69
2.2 Turning OFF the GM862-QUAD
The turning off of the device can be done in three ways:
• by software command (see GM862-QUAD Software User Guide)
• by hardware shutdown
• by hardware unconditional shutdown
When the device is shut down by software command or by hardware shutdown, it issues to the
network a detach request that informs the network that the device will not be reachable any more.
The hardware unconditional shutdown does not issue this request and shuts down immediately the
device.
The hardware unconditional shutdown must not be used during normal operation of the device
since it does not detach the device from the network. It shall be kept as an emergency exit
procedure to be done in the rare case that the device gets stucked waiting for some network or SIM
responses.
If device does not respond to a command in the timeout window, retry issuing the command and if
still no response is received a hardware unconditional shutdown shall be issued and then a restart.
2.2.1.1 Hardware shutdown
To turn OFF the GM862-QUAD the pin ON# must be tied low for at least 1 second and then
released.
The same circuitry and timing for the power on shall be used.
The device shuts down after the release of the ON# pin.
TIP: To check if the device has powered off, the hardware line PWRCTL should be monitored. When
PWRCTL goes low, the device has powered off.
2.2.1.2 Hardware Unconditional Reset
To unconditionally turn OFF the GM862-QUAD the pin RESET# must be tied low for at least 200
milliseconds and then released.
The maximum current that can be drained from the ON# pin is 0,15 mA.
A simple circuit to do it is:
RESET#
Unconditional Power OFF
impulse
GND
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 8 of 69
NOTE: don't use any pull up resistor on the RESET# line nor any totem pole digital output. Using pull
up resistor may bring to latch up problems on the GM862-QUAD power regulator and improper
functioning of the module. The line RESET# must be connected only in open collector configuration.
TIP: The unconditional hardware reset should be always implemented on the boards and software
should use it as an emergency exit procedure.
For example:
1- Let's assume you need to drive the RESET# pin with a totem pole output of a +3/5 V
microcontroller (uP_OUT2):
Unconditional Reset
impulse
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 9 of 69
3 Power Supply
The power supply circuitry and board layout are the most important part in the full product design
and they strongly reflect on the product overall performances, hence read carefully the requirements
and the guidelines that will follow for a proper design.
3.1Power Supply Requirements
The GM862-QUAD power requirements are:
• Nominal Supply Voltage: 3.8 V
• Max Supply Voltage: 4.2 V
• Supply voltage range: 3.4 V - 4.2 V
• Max Peak current consumption (impulsive): 1.9 A
• Max Average current consumption during transmission (rms): 350 mA
• Average current during Power Saving: ≈4 mA
• Average current during idle (Power Saving disabled) ≈17 mA
The GSM system is made in a way that the RF transmission is not continuous, else it is packed into
bursts at a base frequency of about 216 Hz, the relative current peaks can be as high as about 2A.
Therefore the power supply has to be designed in order to withstand with these current peaks
without big voltage drops; this means that both the electrical design and the board layout must be
designed for this current flow.
If the layout of the PCB is not well designed a strong noise floor is generated on the ground and the
supply; this will reflect on all the audio paths producing an audible annoying noise at 216 Hz; if the
voltage drop during the peak current absorption is too much, then the device may even shutdown as
a consequence of the supply voltage drop.
TIP: The electrical design for the Power supply should be made ensuring it will be capable of a peak
current output of at least 2 A.
3.2 General Design Rules
The principal guidelines for the Power Supply Design embrace three different design steps:
- the electrical design
- the thermal design.
- the PCB layout.
Telit GM862-QUAD/-QUAD-PY
Hardware User Guide
1vv0300692, Rev. ISSUE#0, - 04/10/2005
Reproduction forbidden without DAI Telecom written authorization – All Right reserved – Right of modification reserved page 10 of 69
3.2.1 Electrical design Guidelines
The electrical design of the power supply depends strongly from the power source where this power
is drained. We will distinguish them into three categories:
• +5V input (typically PC internal regulator output)
• +12V input (typically automotive)
• Battery
3.2.1.1 + 5V input Source Power Supply Design Guidelines
• The desired output for the power supply is 3.8V, hence there's not a big difference between the
input source and the desired output and a linear regulator can be used. A switching power
supply will not be suited because of the low drop out requirements.
• When using a linear regulator, a proper heat sink shall be provided in order to dissipate the
power generated.
• A Bypass low ESR capacitor of adequate capacity must be provided in order to cut the current
absorption peaks close to the GM862-QUAD, a 100μF tantalum capacitor is usually suited.
• Make sure the low ESR capacitor on the power supply output (usually a tantalum one) is rated
at least 10V.
• A protection diode should be inserted close to the power input, in order to save the GM862-
QUAD from power polarity inversion.
An example of linear regulator with 5V input is:
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