Telit Wireless Solutions GE863-QUAD, GE863-PY manual Car Kit Speakerphone Design

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GE863-QUAD

GE863-PY

1vv0300715 Rev. 1 - 19/09/06

8.6 Car Kit Speakerphone Design

For the car kit speaker phone function the power output requirement is usually at least 4W, therefore an amplifier is needed to boost the GE863-QUAD / PY output.

The design of the amplifier shall comply with the following guidelines:

•The input to the amplifier MUST be taken from the “Ear_HF” audio path of the GE863-QUAD / PY, because of its echo canceller parameters suited to a car cabin use.

•The amplifier shall have a gain of 30-40 times (29-32 dB) to provide the desired output power of 5- 10W with the signal from the GE863-QUAD / PY “Ear_HF” audio output lines.

•If the amplifier has a fixed gain then it can be adjusted to the desired value by reducing the input signal with a resistor divider network.

•The amplifier shall have a mute control to be used while not in conversation. This results in two benefits: eliminating the background noise when not in conversation and saving power.

•The power to the amplifier should be decoupled as much as possible from the GE863-QUAD / PY power supply, by either keeping separate wires and placing bypass capacitors of adequate value close to the amplifier power input pads.

•The biasing voltage of the amplifier shall be stabilized with a low ESR (e.g. a tantalum) capacitor of adequate value.

NOTE: The GE863-QUAD / PY audio path connected to the car kit hands-free amplifier MUST be “Ear_HF” one, otherwise the echo cancellation will not be done due to the difference in the echo canceller characteristics of the GE863-QUAD / PY internal audio path from the external audio path.

Example of car kit amplifier schematic.

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Contents GE863-QUAD GE863-PY Hardware User Guide Contents 10.2 10.110.3 10.413.1 12.113.2 This document is relating to the following products Overview PIN-OUT GE863 module connectionsPin Signal Function Internal Type Pull up Pin Signal Function Internal Type Pins Layout Turning on the GE863-QUAD/PY Hardware CommandsTurning off of the device can be done in two ways Turning OFF the GE863-QUAD/PYHardware shutdown Hardware Unconditional RebootGE863-QUAD 1Power Supply Requirements Power SupplyGE863-QUAD/PY power requirements are Electrical design Guidelines 2General Design RulesAn example of linear regulator with 5V input is 1.2 + 12V input Source Power Supply Design GuidelinesAn example of switching regulator with 12V input is Battery Source Power Supply Design GuidelinesBattery Charge control Circuitry Design Guidelines Thermal Design Guidelines Power Supply PCB layout Guidelines GSM Antenna Requirements AntennaSerial Ports GSM Antenna installation GuidelinesGSM Antenna PCB line Guidelines Level Min Max Absolute Maximum Ratings -Not Functional Parameter Min MaxNumber Pad Number Signals in the Uart connector on the EVK are17-28-36 Ground 45-48-50-56 Clear to Send Output from the GE863-QUAD/PY that2MODEM Serial Port 2 Python Debug It is available on the following pins3RS232 level translation An example of level translation circuitry of this kind is 5V Uart level translation GE863-QUAD Audio Section Overview GM863-GPS Echo canceller type Handset Microphone Paths Characteristic and RequirementsEcho canceller type Car kit hands-free + 20dBYou can set GA= +20dB to use standard resistor values That meansTIP environment consideration Other considerations General Design RulesBalanced Microphone Biasing Microphone BiasingUnbalanced Microphone Biasing GE863-QUAD Buffered Balanced Mic Microphone BufferingSample circuit can be Buffer gain is given by the formula Gain = RR604605 = RR607606Buffered Unbalanced Single Ended Microphone Buffer bandwidth at -3dB shall be 4KHz Freq . = 2π * R719* C726 2π * R711* C727GE863-QUAD Short description Output Lines SpeakerSW volume level step Number of SW volume steps Output Lines CharacteristicsNoise Filtering Handset Earphone Design An example of internal Ear amplifier could be Hands-Free Earphone Low Power DesignCar Kit Speakerphone Design Short Description Evaluation Kit for Telit Modules EVK2@ 350mW 2 EVK2 Audio Lines CharacteristicsESD Data IntegritySIM Supply SchematicLayout Using a Gpio Pad as Output Using a Gpio Pad as InputGeneral Purpose I/O Using the Buzzer Output GPIO7 10.3Using the Alarm Output GPIO611.1DAC Converter DAC and ADC sectionDescription Min Max UnitsCommand is AT#DAC=enable,value An AT command is available to use the DAC functionEnabling DAC Low Pass Filter ExampleInput Voltage range AD conversion Bits Resolution Using ADC Converter11.2ADC Converter 12.1Transchip Camera CameraType Sensitivity LuxCamera Interface Connectors Camera Physical Detail & Connector Camera Socket Connector Camera Board Module Main Block Diagram for supported cameras Schematic Diagrams for supported camera Example usage script for camera Camera setting shown here are the defaults onesTaking an reading a photo Mounting the GE863-QUAD / PY on the Application Board 13.2Module Finishing & Dimensions13.1General Lead-free Alloy Surface finishing Ni/Au for all test padsRecommended foot print for the application Stencil Debug of the GE863 in ProductionPCB pad Design Solder paste Following is the recommended solder reflow profile 13.2.6 GE863-QUAD / PY Solder ReflowGE863-QUAD Section A-A Packing SystemModules orientation on tray Moisture Sensibility Conformity Assessment Issues Safety Recommandations Revision Date Changes Document Change Log21/02/06 19/09/06