User Manual

GE863-PRO
3
Hardware User Guide
1vv0300773a Rev. 1 DRAFT - 24/04/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 3 of 82
7.2 RS232 level translation........................................................................................................ 42
8 Audio Section Overview ................................................................................................45
8.1 Microphone Paths Characteristic and Requirements............................................................ 46
8.2 General Design Rules.......................................................................................................... 49
8.3 Other considerations............................................................................................................ 49
8.4 Microphone Biasing ............................................................................................................. 50
8.4.1 Balanced Microphone Biasing ........................................................................................................50
8.4.2 Unbalanced Microphone Biasing....................................................................................................51
8.5 Microphone Buffering........................................................................................................... 53
8.5.1 Buffered Balanced Mic....................................................................................................................53
8.5.2 Buffered Unbalanced (Single Ended) Microphone .........................................................................55
9 OUTPUT LINES (Speaker)..............................................................................................58
9.1 Short description.................................................................................................................. 58
9.2 Output Lines Characteristics................................................................................................ 59
9.3 General Design Rules.......................................................................................................... 60
9.3.1 Noise Filtering.................................................................................................................................60
9.4 Handset Earphone Design................................................................................................... 61
9.5 Hands-Free Earphone (Low Power) Design......................................................................... 62
9.6 Car Kit Speakerphone Design.............................................................................................. 63
9.7 The Evaluation Kit for Telit GE863-PRO
3
Modules............................................................... 64
9.7.1 Short Description ............................................................................................................................64
10 General Purpose I/O.......................................................................................................65
10.1 Using a GPIO Pad as INPUT ........................................................................................... 66
10.2 Using a GPIO Pad as OUTPUT........................................................................................ 66
10.3 Using the RF Transmission Control GPIO7...................................................................... 66
10.4 Using the RFTXMON Output GPIO3................................................................................ 66
10.5 Using the Alarm Output.................................................................................................... 67
10.6 Using the Buzzer Output GPIO4....................................................................................... 67
10.7 Indication of network service availability........................................................................... 68
10.8 RTC Bypass out............................................................................................................... 69
10.9 VAUX1 power output........................................................................................................ 69
11 Mounting the GE863-PRO
3
on the Application Board.................................................70
11.1 General ............................................................................................................................ 70
11.1.1 Recommended footprint for the application....................................................................................71
11.1.2 Stencil .............................................................................................................................................72
11.1.3 PCB pad Design .............................................................................................................................72
11.1.4 Solder paste....................................................................................................................................73