Telit Wireless Solutions GE863-PY, GE863-QUAD manual General Design Rules, Noise Filtering

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GE863-QUAD

GE863-PY

1vv0300715 Rev. 1 - 19/09/06

8.3 General Design Rules

There are several configurations for the audio output path, but the various design requirements can be grouped into three different categories:

•handset earphone (low power, typically a handset)

•hands-free earphone (low power, typically a earphone)

•car kit speakerphone (high power, typically a speaker)

The three groups have different power requirements, usually the first two applications need only few mW of power, which can be directly drained from the GE863-QUAD / PY pads, provided a suited speaker is used. This direct connect design is the cheaper and simpler solution and will be suited for the most of the earphone design requirements. There's no need to decouple the output ear lines if a suited earpiece is connected. For the last group, the speakerphone, a power amplifier is required to raise the output power up to 5-10W required in a car cabin application.

All the designs shall comply with the following guidelines:

•Where possible use a bridged earphone circuitry, to achieve the maximum power output from the device.

•Keep the earphone traces on the PCB and wires as short as possible.

•If your application requires a single ended earpiece and you want a direct connection, then leave one of the two output lines open and use only the other referred to ground. Remember that in this case the power output is 4 times lower than the bridged circuit and may not be enough to ensure a good voice volume.

•Make sure that the earphone traces in the PCB don't cross or run parallel to noisy traces (especially the power line)

•The cable to the speaker shall be a twisted pair with both the lines floating for the bridged output type, shielded with the shield to ground for the single ended output type.

8.3.1 Noise Filtering

The I/O of the PCB should have a noise filter close to the connector, to filter the high frequency GSM noise. The filter can be a Π formed by 2 capacitor and a inductance, with the one capacitor of 39pF - 0603 case , and the other capacitor of 1nF - 0603; the inductance shall have a value of 39μH .

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Contents GE863-QUAD GE863-PY Hardware User Guide Contents 10.3 10.110.2 10.413.1 12.113.2 This document is relating to the following products Overview GE863 module connections PIN-OUTPin Signal Function Internal Type Pull up Pin Signal Function Internal Type Pins Layout Hardware Commands Turning on the GE863-QUAD/PYTurning OFF the GE863-QUAD/PY Turning off of the device can be done in two waysHardware Unconditional Reboot Hardware shutdownGE863-QUAD 1Power Supply Requirements Power SupplyGE863-QUAD/PY power requirements are 2General Design Rules Electrical design Guidelines1.2 + 12V input Source Power Supply Design Guidelines An example of linear regulator with 5V input isBattery Source Power Supply Design Guidelines An example of switching regulator with 12V input isBattery Charge control Circuitry Design Guidelines Thermal Design Guidelines Power Supply PCB layout Guidelines Antenna GSM Antenna RequirementsSerial Ports GSM Antenna installation GuidelinesGSM Antenna PCB line Guidelines Absolute Maximum Ratings -Not Functional Parameter Min Max Level Min Max17-28-36 Ground 45-48-50-56 Signals in the Uart connector on the EVK areNumber Pad Number 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 Car kit hands-free Microphone Paths Characteristic and RequirementsEcho canceller type Handset + 20dBThat means You can set GA= +20dB to use standard resistor valuesTIP environment consideration General Design Rules Other considerationsMicrophone Biasing Balanced Microphone BiasingUnbalanced Microphone Biasing GE863-QUAD Buffered Balanced Mic Microphone BufferingSample circuit can be Gain = RR604605 = RR607606 Buffer gain is given by the formulaBuffered Unbalanced Single Ended Microphone Freq . = 2π * R719* C726 2π * R711* C727 Buffer bandwidth at -3dB shall be 4KHzGE863-QUAD Output Lines Speaker Short descriptionOutput Lines Characteristics SW volume level step Number of SW volume stepsNoise Filtering Handset Earphone Design Hands-Free Earphone Low Power Design An example of internal Ear amplifier could beCar Kit Speakerphone Design Evaluation Kit for Telit Modules EVK2 Short Description2 EVK2 Audio Lines Characteristics @ 350mWData Integrity ESDSchematic SIM SupplyLayout Using a Gpio Pad as Output Using a Gpio Pad as InputGeneral Purpose I/O 10.3Using the Alarm Output GPIO6 Using the Buzzer Output GPIO7Description DAC and ADC section11.1DAC Converter Min Max UnitsEnabling DAC An AT command is available to use the DAC functionCommand is AT#DAC=enable,value Low Pass Filter ExampleInput Voltage range AD conversion Bits Resolution Using ADC Converter11.2ADC Converter Type Camera12.1Transchip Camera 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 Surface finishing Ni/Au for all test pads Lead-free AlloyRecommended foot print for the application Stencil Debug of the GE863 in ProductionPCB pad Design Solder paste 13.2.6 GE863-QUAD / PY Solder Reflow Following is the recommended solder reflow profileGE863-QUAD Packing System Section A-AModules orientation on tray Moisture Sensibility Conformity Assessment Issues Safety Recommandations 21/02/06 Document Change LogRevision Date Changes 19/09/06