Telit Wireless Solutions LM940 Guide

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LM940
HW Design Guide
1VV0301352 Rev. 18 –2022-01-04
Telit Technical Documentation

LM940 Hardware Design Guide
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APPLICABILITY TABLE
PRODUCTS
LM940 1.0
LM940 2.0
Note: The main difference between LM940 HW Versions 1.0 and 2.0
is the pin-out. The two versions are slightly different in terms of
POWER ON/OFF control.
For more details. refer to the chapter 3. Pins Allocation and 6. Digital
Section

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CONTENTS
APPLICABILITY TABLE 2
CONTENTS 3
1. INTRODUCTION 8
Scope 8
Audience 8
Contact Information, Support 8
Symbol Conventions 10
Related Documents 10
2. GENERAL PRODUCT DESCRIPTION 11
Overview 11
Product Variants and Frequency Bands 11
2.2.1. RF Bands per Regional Variant 11
2.2.1.1. Generic Image Frequency Bands and CA Combinations 11
2.2.1.2. AT and T Image Frequency Bands and CA Combinations 12
2.2.1.3. Verizon Image Frequency Bands and CA Combinations 12
2.2.1.4. Sprint Image Frequency Bands and CA Combinations 12
Target Market 13
Main Features 13
Block Diagram 14
TX Output Power 14
RX Sensitivity 15
GNSS Receiver Specifications 15
Mechanical Specifications 16
2.9.1. Dimensions 16
2.9.2. Weight 16
Environmental Requirements 17
2.10.1. Temperature Range 17
2.10.2. RoHS Compliance 17
3. PINS ALLOCATION 18
Pin-Out 18

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3.1.1. LM940 1.0 Pin-Out 18
3.1.2. LM940 2.0 Pin-Out 20
LM940 Signals That Must Be Connected 23
Pin Layout 24
4. POWER SUPPLY 26
Power Supply Requirements 26
Power Consumption 26
General Design Rules 27
4.3.1. Electrical Design Guidelines 27
4.3.1.1. + 5V Input Source Power Supply –Design Guidelines 27
4.3.2. Thermal Design Guidelines 27
4.3.3. Power Supply PCB Layout Guidelines 28
RTC 29
Reference Voltage 29
Internal LDO for GNSS Bias 30
5. ELECTRICAL SPECIFICATIONS 31
Absolute Maximum Ratings –Not Operational 31
Recommended Operating Conditions 31
6. DIGITAL SECTION 32
Logic Levels 32
6.1.1. 1.8V Pins –Absolute Maximum Ratings 32
6.1.2. 1.8V Standard GPIOs 32
6.1.3. 1.8V SIM Card Pins 33
6.1.4. 2.85V Pins –Absolute Maximum Ratings 33
6.1.5. SIM Card [email protected] 33
Power On 33
6.2.1. Initialization and Activation State 34
Power Off 35
6.3.1. Graceful Shutdown 35
6.3.1.1. Graceful Shutdown by AT Command 35
6.3.2. Fast Shutdown 36

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6.3.2.1. Fast Shutdown by AT Command 36
6.3.2.2. Fast Shutdown by GPIO 37
6.3.3. Unconditional Shutdown (Support Only on LM940 2.0) 38
Reset 39
6.4.1. Graceful Reset 40
6.4.2. Unconditional Hardware Reset 40
Dying Gasp 41
Communication Ports 41
6.6.1. USB Interface 42
6.6.2. SIM Interface 44
6.6.2.1. SIM Schematic Example 45
6.6.3. Control Signals 46
6.6.3.1. W_DISABLE_N 46
6.6.3.2. WAN_LED_N 46
6.6.4. General Purpose I/O 47
6.6.4.1. Using a GPIO Pin as Input 47
6.6.4.2. Using a GPIO Pin as Output 48
6.6.4.3. Dedicated I/O 48
6.6.5. I2C –Inter-Integrated Circuit 49
Using the Temperature Monitor Function 49
7. RF SECTION 50
Antenna Requirements 50
Main Antenna Requirements 50
Antenna Diversity Requirements 50
GNSS Receiver 51
7.4.1. GNSS RF Front End Design 51
Antenna Connection 52
7.5.1. Antenna Connector 52
7.5.2. Antenna Cable 53
7.5.3. Antenna Installation Guidelines 54
8. MECHANICAL DESIGN 55
General 55

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Finishing and Dimensions 55
Drawing 55
9. APPLICATION GUIDE 56
Debug of the LM940 Module in Production 56
Bypass Capacitor on Power Supplies 56
EMC Recommendations 57
10. PACKAGING 59
Tray 59
11. CONFORMITY ASSESTMENT ISSUES 61
Approval Summary 61
RED Approval 61
11.2.1. RED Declaration of Conformity 61
FCC Certificates 61
IC Certificates 61
FCC/IC Regulatory Notices 61
RED Regulatory Notices 64
12. REFERENCE TABLE OF RF BANDS CHARACTERISTICS 66
13. PRODUCT AND SAFETY INFORMATION 68
Copyrights and Other Notices 68
13.1.1. Copyrights 68
13.1.2. Computer Software Copyrights 68
Usage and Disclosure Restrictions 69
13.2.1. License Agreements 69
13.2.2. Copyrighted Materials 69
13.2.3. High Risk Materials 69
13.2.4. Trademarks 70
13.2.5. 3rd Party Rights 70
13.2.6. Waiver of Liability 70
Safety Recommendations 71
14. GLOSSARY 72

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15. DOCUMENT HISTORY 73

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1. INTRODUCTION
Scope
This document introduces the Telit LM940 module and presents possible and
recommended hardware solutions for developing a product based on the LM940 module.
All the features and solutions detailed in this document are applicable to all LM940
variants, where “LM940” refers to the variants listed in the Applicability Table.
If a specific feature is applicable to a specific product only, it will be clearly marked.
Note: LM940 refers to all modules listed in the Applicability Table.
This document takes into account all the basic functions of a wireless module; a valid
hardware solution is suggested for each function, and incorrect solutions and common
errors to be avoided are pointed out.
Obviously, this document cannot embrace every hardware solution or every product that
can be designed. Where the suggested hardware configurations need not be considered
mandatory, the information given should be used as a guide and a starting point for
properly developing a product using the Telit LM940 module.
Note: The integration of the WCDMA/HSPA+/LTE LM940 cellular
module within a user application must be carried out according to the
design rules described in this manual.
Audience
This document is intended for Telit customers, especially system integrators, about to
implement their applications using the Telit LM940 module.
Contact Information, Support
For general contact, technical support services, technical questions and report of
documentation errors contact Telit Technical Support at:
• TS[email protected]
• TS[email protected]
• TS[email protected]
• TS[email protected]
• TS[email protected]
Alternatively, use:

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https://www.telit.com/contact-us
For detailed information about where you can buy the Telit modules or for
recommendations on accessories and components visit:
https://www.telit.com
Our aim is to make this guide as helpful as possible. Keep us informed of your comments
and suggestions for improvements.
Telit appreciates the user feedback on our information.

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Symbol Conventions
Danger: This information MUST be followed or catastrophic
equipment failure or personal injury may occur.
Warning: Alerts the user on important steps about the module
integration.
Note/Tip: Provides advice and suggestions that may be useful when
integrating the module.
Electro-static Discharge: Notifies the user to take proper grounding
precautions before handling the product.
Table 1: Symbol Conventions
All dates are in ISO 8601 format, that is YYYY-MM-DD.
Related Documents
•LM940 SW User Guide, 1VV0301343
•LM940 AT Commands Reference Guide, 80545ST10791A
•Generic EVB HW User Guide, 1VV0301249
•LM940 Interface Board HW User Guide, 1VV0301384
•SIM Integration Design Guide Application Note Rev10, 80000NT10001A
•Antenna Detection Application Note, 80000NT10002A