Microphone Buffering | Telit Wireless Solutions GE863-QUAD guide

GE863-QUAD

GE863-PY

1vv0300715 Rev. 1 - 19/09/06

7.5 Microphone Buffering

As seen previously, a microphone shall be connected to the input pins of the GE863-QUAD / PY through a buffer amplifier that boosts the signal level to the required value.

Again the buffered microphone circuitry can be balanced or unbalanced: where possible it is always preferable a balanced solution. The buffering circuit shall be placed close to the microphone or close to the microphone wire connector.

7.5.1 Buffered Balanced Mic

A sample circuit can be:

+20dB

15K

270pFto

GE863

15K

270pF

This circuit has a gain of 10 times (+20 dB), and is therefore suited for the “Mic_MT “ input if you have

amicrophone with a sensitivity close to the suggested one (-45 dBVrms/Pa). If your microphone has a different sensitivity or if the buffer is connected to the “Mic_HF “ inputs , then a gain adjustment shall be done by changing resistors R604 and R606 ( if the required value is not a standard one , you can change R605 e R607 ) and as a consequence the capacitors C636 and C637 to maintain the bandwidth 150-4000Hz (at -3dB).

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Telit Wireless Solutions GE863-QUAD, GE863-PY manual Microphone Buffering, Buffered Balanced Mic, Sample circuit can be

Contents

GE863-QUAD GE863-PY Hardware User Guide Contents 10.4 10.110.2 10.3 12.1 13.113.2 This document is relating to the following products Overview PIN-OUT GE863 module connections Pin Signal Function Internal Type Pull up Pin Signal Function Internal Type Pins Layout Turning on the GE863-QUAD/PY Hardware Commands Turning off of the device can be done in two ways Turning OFF the GE863-QUAD/PY Hardware shutdown Hardware Unconditional Reboot GE863-QUAD Power Supply 1Power Supply RequirementsGE863-QUAD/PY power requirements are Electrical design Guidelines 2General Design Rules An example of linear regulator with 5V input is 1.2 + 12V input Source Power Supply Design Guidelines An example of switching regulator with 12V input is Battery Source Power Supply Design Guidelines Battery Charge control Circuitry Design Guidelines Thermal Design Guidelines Power Supply PCB layout Guidelines GSM Antenna Requirements Antenna GSM Antenna installation Guidelines Serial PortsGSM Antenna PCB line Guidelines Level Min Max Absolute Maximum Ratings -Not Functional Parameter Min Max Clear to Send Output from the GE863-QUAD/PY that Signals in the Uart connector on the EVK areNumber Pad Number 17-28-36 Ground 45-48-50-56 It is available on the following pins 2MODEM Serial Port 2 Python Debug3RS232 level translation An example of level translation circuitry of this kind is 5V Uart level translation GE863-QUAD Audio Section Overview GM863-GPS + 20dB Microphone Paths Characteristic and RequirementsEcho canceller type Handset Echo canceller type Car kit hands-free You can set GA= +20dB to use standard resistor values That means TIP environment consideration Other considerations General Design Rules Balanced Microphone Biasing Microphone Biasing Unbalanced Microphone Biasing GE863-QUAD Microphone Buffering Buffered Balanced MicSample circuit can be Buffer gain is given by the formula Gain = RR604605 = RR607606 Buffered Unbalanced Single Ended Microphone Buffer bandwidth at -3dB shall be 4KHz Freq . = 2π * R719* C726 2π * R711* C727 GE863-QUAD Short description Output Lines Speaker SW volume level step Number of SW volume steps Output Lines Characteristics Noise Filtering Handset Earphone Design An example of internal Ear amplifier could be Hands-Free Earphone Low Power Design Car Kit Speakerphone Design Short Description Evaluation Kit for Telit Modules EVK2 @ 350mW 2 EVK2 Audio Lines Characteristics ESD Data Integrity SIM Supply Schematic Layout Using a Gpio Pad as Input Using a Gpio Pad as OutputGeneral Purpose I/O Using the Buzzer Output GPIO7 10.3Using the Alarm Output GPIO6 Min Max Units DAC and ADC section11.1DAC Converter Description Low Pass Filter Example An AT command is available to use the DAC functionCommand is AT#DAC=enable,value Enabling DAC Using ADC Converter Input Voltage range AD conversion Bits Resolution11.2ADC Converter Sensitivity Lux Camera12.1Transchip Camera Type Camera Interface Connectors Camera Physical Detail & Connector Camera Socket Connector Camera Board Module Main Block Diagram for supported cameras Schematic Diagrams for supported camera Camera setting shown here are the defaults ones Example usage script for cameraTaking an reading a photo 13.2Module Finishing & Dimensions Mounting the GE863-QUAD / PY on the Application Board13.1General Lead-free Alloy Surface finishing Ni/Au for all test pads Recommended foot print for the application Debug of the GE863 in Production StencilPCB pad Design Solder paste Following is the recommended solder reflow profile 13.2.6 GE863-QUAD / PY Solder Reflow GE863-QUAD Section A-A Packing System Modules orientation on tray Moisture Sensibility Conformity Assessment Issues Safety Recommandations 19/09/06 Document Change LogRevision Date Changes 21/02/06