User's Manual
Table Of Contents
- GC864 QUAD V2andGC864 DUAL V2Hardware User Guide
- APPLICABILITY TABLE
- 1 Introduction
- 2. Overview
- 3. GC864 Mechanical Dimensions
- 4. GC864-QUAD V2 / GC864-DUAL V2 Module Connections
- 5. Hardware Commands
- 6. Power Supply
- 7. Antenna
- 8. Logic Level Specifications
- 9. Serial Ports
- 10. Audio Section Overview
- 11. General Purpose I/O
- 11.1. GPIO Logic Levels
- 11.2. Using a GPIO Pad as INPUT
- 11.3. Using a GPIO Pad as OUTPUT
- 11.4. Using the RF Transmission Control GPIO4
- 11.5. Using the RFTXMON Output GPIO5
- 11.6. Using the Alarm Output GPIO6
- 11.7. Using the Buzzer Output GPIO7
- 11.8. Magnetic Buzzer Concepts
- 11.9. Using the Temperature Monitor Function
- 11.10. Indication of Network Service Availability
- 11.11. RTC Bypass Out
- 11.12. DAC Converter
- 11.13. ADC Converter
- 12. Assembly the GC864-QUAD V2 / GC864-DUAL V2 on the Board
- 13. Packing System
- 14. Conformity Assessment Issues
GC864 Hardware User Guide
1vv0300874 Rev.0 – 2010-01-25
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved. Page 43 of 64
10.2. Electrical Characteristics
TIP: Being the microphone circuitry the more noise sensitive, its design and layout
must be done with particular care. Both microphone paths are balanced and the OEM
circuitry must be balanced designed to reduce the common mode noise typically
generated on the ground plane. However the customer can use the unbalanced
circuitry for its particular application.
10.2.1. Input Lines Characteristics
“MIC_MT” and “MIC_HF” differential microphone paths
Line Coupling AC*
Line Type Balanced
Differential input voltage
1,03V
pp
@
Mic G=0dB
Gain steps 7
Gain increment 6dB per step
Coupling capacitor
100nF
Differential input resistance
50K
Input capacitance • 10pF
(*) WARNING : AC means that the signals from the microphone have to be
connected to input lines of the module through capacitors which value has to
be 100nF. Not respecting this constraint, the input stages will be damaged.
WARNING: when particular OEM application needs a
Single Ended Input
configuration, it is forbidden connecting the unused input directly to Ground,
but only through a 100nF capacitor. Don’t forget that the useful input signal will be
halved in
Single Ended
Input
configuration.