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GM862-GPS Hardware User Guide
1vv0300728 Rev. 0 - 27/04/06
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 2 of 55
Contents
1 Overview ...........................................................................................................................4
2 Hardware Commands ......................................................................................................5
2.1 Turning ON the GM862-GPS..................................................................................................5
2.2 Turning OFF the GM862-GPS ................................................................................................7
2.2.1 Hardware shutdown..........................................................................................................................7
2.2.2 Hardware Unconditional Reboot.......................................................................................................8
3 Power Supply .................................................................................................................10
3.1 Power Supply Requirements...............................................................................................10
3.2 General Design Rules ..........................................................................................................11
3.2.1 Electrical design Guidelines........................................................................................................... 11
3.2.1.1 + 5V input Source Power Supply Design Guidelines ................................................................ 11
3.2.1.2 + 12V input Source Power Supply Design Guidelines .............................................................. 13
3.2.1.3 Battery Source Power Supply Design Guidelines ..................................................................... 14
3.2.1.4 Battery Charge control Circuitry Design Guidelines .................................................................. 15
3.2.2 Thermal Design Guidelines ........................................................................................................... 17
3.2.3 Power Supply PCB layout Guidelines ........................................................................................... 18
4 Serial Ports .....................................................................................................................19
4.1 level translation ....................................................................................................................21
4.2 5V UART level translation....................................................................................................23
5 Audio Section Overview ................................................................................................25
5.1 Microphone paths characteristic and requirements .........................................................27
5.2 General Design Rules ..........................................................................................................30
5.3 Other considerations . .........................................................................................................30
5.4 Microphone Biasing .............................................................................................................31
5.4.1 Balanced Microphone biasing........................................................................................................ 31
5.4.2 Unbalanced Microphone biasing ...................................................................................................32
5.5 Microphone buffering...........................................................................................................34
5.5.1 Buffered Balanced Mic................................................................................................................... 34
5.5.2 Buffered Unbalanced (Single Ended) Microphone . ...................................................................... 36
6 OUTPUT LINES (Speaker)..............................................................................................39
6.1 Short description..................................................................................................................39
6.2 Output lines characteristics . .............................................................................................40
6.3 General Design rules............................................................................................................41