HE920 Hardware User Guide
1vv0301014 Rev.9 – 2014-01-23
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved.
Page 6 of 84
5.2.1.
Electrical Design Guidelines ............................... 35
5.2.1.1.
+ 5V Input Source Power Supply Design Guidelines ........ 35
5.2.1.2.
+ 12V Input Source Power Supply Design Guidelines ....... 36
5.2.1.3.
Battery Source Power Supply Design Guidelines ........... 38
5.2.2.
Thermal Design Guidelines .................................. 39
5.2.3.
Power Supply PCB Layout Guidelines ......................... 40
6.
Antenna(s) .................................................. 42
6.1.
GSM/WCDMA Antenna Requirements ........................... 42
6.2.
GSM/WCDMA Antenna – PCB line Guidelines .................. 43
6.3.
GSM/WCDMA Antenna – Installation Guidelines .............. 44
6.4.
Antenna Diversity Requirements ........................... 44
6.5.
GPS/GNSS Antenna Requirements ............................ 45
6.5.1.
Combined GPS/GNSS Antenna .................................. 45
6.5.2.
Linear and Patch GPS/GNSS Antenna .......................... 45
6.5.3.
LNA and Front End Design Considerations .................... 45
6.5.4.
GPS/GNSS Antenna - PCB Line Guidelines ..................... 47
6.5.5.
GPS/GNSS Antenna – Installation Guidelines ................. 48
7.
Logic Level Specifications .................................. 49
7.1.
Reset Signal(Module Restart) ............................. 50
8.
USB Port .................................................... 51
9.
Serial Ports ................................................ 52
9.1.
Modem Serial Port 1 ...................................... 53
9.2.
Modem Serial Port 2 ...................................... 54
9.3.
RS232 Level Translation .................................. 54
10.
Audio Section Overview ...................................... 56
10.1.
Analog Audio ........................................... 56
10.2.
Digital Audio .......................................... 56
10.2.1.
CODEC Example ............................................ 56
11.
General Purpose I/O ......................................... 57
11.1.
Logic Level Specifications ............................. 58
11.2.
Using a GPIO Pad as Input .............................. 58
11.3.
Using a GPIO Pad as Output ............................. 59
11.4.
Using the Temperature Monitor Function ................. 60
