Telit Wireless Solutions LM940 Guida

LM940

HW Design Guide

1VV0301352 Rev. 18 –2022-01-04

Telit Technical Documentation

LM940 Hardware Design Guide

1VV0301352 Rev. 18 Page 2of 75 2022-01-04

Not Subject to NDA

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

LM940 Hardware Design Guide

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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:

•

•

•

•

•

Alternatively, use:

LM940 Hardware Design Guide

1VV0301352 Rev. 18 Page 9of 75 2022-01-04

Not Subject to NDA

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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1VV0301352 Rev. 18 Page 10 of 75 2022-01-04

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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

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