Hardware Guide
Table Of Contents
- Introduction
- 2. Overview
- 3. GE865 Mechanical Dimensions
- 4. GE865 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. Indication of network service availability
- 11.9. RTC Bypass out
- 11.10. External SIM Holder Implementation
- 12. DAC and ADC section
- 13. Mounting the GE865 on your Board
- 14. Packing system
- 15. Conformity Assessment Issues
- 17. Document History
GE865 Hardware User Guide
1vv0300799 Rev.15– 2012-04-23
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 51 of 77
10.1. 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 particular application.
10.1.1. Input Lines
“MIC 1” differential microphone path
Line Coupling AC*
Line Type Balanced
Coupling capacitor ≥ 100nF
Differential input resistance 50kΩ
Differential input voltage ≤ 1,03V
pp
@ MicG=0dB
(*) 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 capacitor which
value has to be ≥ 100nF..
Don’t forget that in Single Ended configuration the useful input signal will be halved.