Thermal guidelines XE922-3gr - Telit: IoT Solutions Provider

80504NT11473A Rev.0.1 2016-11-03

THERMAL GUIDELINES XE922-3GR

THERMAL GUIDELINES XE922-3GR 80504NT11473A Rev.0.1 • 2016-11-03 2 of 17

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APPLICABILITY TABLE

PRODUCTS HE922-3GR and WE922-3GR



SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE

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These Specifications are general guidelines pertaining to product selection and application and may not

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Copyright © Telit Communications PLC.



CONTENTS

1 Introduction 6

1.1 Scope 6

1.2 Audience 6

1.3 Contact Information, Support 6

1.4 Text Conventions 7

1.5 Related Documents 7

2 Thermal guidelines 8

2.1 Overview 8

2.2 Hardware guidelines 9

Module to application board connection 9

Module top connection 11

2.3 Software thermal management 13

Software thermal management 13

Thermal probes 13

Throttling configuration 15

3 Document History 16



1 INTRODUCTION

1.1 Scope

This document contains information about power dissipation of the xE922-3GR series modules and

gives recommendations to optimize the thermal design of the application board.

1.2 Audience

This document is intended to PCB layout engineers and Thermal design engineer.

1.3 Contact Information, Support

For general contact, technical support services, technical questions, to report documentation errors and

to order manuals, contact Telit’s Technical Support Center (TTSC) at:

[email protected] if located in North America

For other regions, Collabnet Telit web portal can be used at https://teamforge.telit.com (account can be

asked at [email protected])

Alternatively, use:

http://www.telit.com/en/products/technical-support-center/contact.php

For detailed information about where you can buy the Telit modules or for recommendations on

accessories and components visit:

http://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 feedback from the users of our information.

mailto:[email protected]

https://teamforge.telit.com/

mailto:[email protected]

http://www.telit.com/en/products/technical-support-center/contact.php

http://www.telit.com/



1.4 Text Conventions

Danger – This information MUST be followed or catastrophic equipment failure

or bodily injury may occur.

Caution or Warning – Alerts the user to important points about integrating the

module, if these points are not followed, the module and end user equipment

may fail or malfunction.

Tip or Information – Provides advice and suggestions that may be useful when

integrating the module.

All dates are in ISO 8601 format, i.e. YYYY-MM-DD.

1.5 Related Documents

● 1VV0301272 xE922-3GR Hardware User Guide



2 THERMAL GUIDELINES

2.1 Overview

A good thermal design is expected to provide intended performance at desired real world workloads

while maintaining acceptable temperatures for the internal components. This needs to be done with

mindful tradeoffs between cost, industrial design, structural and thermal requirements. It needs to be

robust enough not to require performance throttling under normal operating conditions. The goal is to

conduct as much heat as possible in order to obtain the best processors speeds for the maximum

possible time.

The following figure is showing a full thermal solution. The xE922-3GR modules have been designed to

optimize the heat transfer in both the top and bottom directions. Software and hardware guidelines are

provided in order to conduct the heat from the module to the external environment and to avoid the

module to reach its critical temperature zone in which it will automatically reboot. This last event is

indeed to be avoided in the final application but allows the system to recover without hardware damages.

The following sections are helping the customer to design the requested solution.

Figure 1 Thermal solution

The extended temperature version of the xE922-3GR is specifying a maximum

operating temperature of 85°C for the case temperature (Tcase) at a maximum

power consumption of 3.3 Watts.



2.2 Hardware guidelines

The xE922-3GR modules have been designed to optimize the heat transfer in both the top and bottom

directions. The two following sections are indicating best practices to make use of these optimizations

to obtain a good hardware thermal solution at system level.

Module to application board connection

The xE922-3GR module PCB has been designed to conduct the heat from the most consuming IC

directly to the ground layers of the module PCB. The large number of ground contact pads on the

backside of the module are available for the final customer to conduct this heat to the application board.

Figure 2 is showing the ground pads repartitions of the xE922-3GR modules.

Figure 2: ground pad position (yellow marks) – top view

It is highly recommended that the application board is having as many thermal ground vias as possible

located right under the module so that the heat can be most effectively transferred to the backside and

spread over a large copper area. The Telit test board has been designed with more than 300 all- through

vias. The repartition of the vias has been optimized regarding the location of the internal components

as depicted in Table 1 and Figure 3.

ZONE NUMBER OF VIAS

3G Power amplifier (3G PA) 20

2G Power amplifier (2G PA) 36

Digital BaseBand (SoC) 86

Analog RF + PMU (PMIC) 50

Ground area in the middle of the module

100

Table 1 : Number of vias of Telit test board



Figure 3 : test board bottom layer with thermal vias indications – top view

The bottom layer of the Telit test board is also including a full copper area plane about the size of the

module to help the mounting of a heatsink or for the connection to the chassis via a pedestal.

Figure 4 : bottom layer of the test board – heat conduction with housing

The layers stack-up of the Telit test board is also provided on Figure 5 for customer reference.



Figure 5 : layers stack-up of test board

This board configuration has shown strong heat conduction capability during all thermal tests carried by

Telit. Customer is strongly advised to follow those previous guidelines for its own application board

design. The use of metal heatsink - as part of the housing - directly attached to the ground plane on the

backside of the application PCB is also strongly recommended. Indeed, this implies to use thermal

grease or thermal gap pad in between the board and the housing to ensure a good thermal conduction.

On the application board, any other heat-generating components shall be placed far away (3 - 4 cm)

from the module.

Module top connection

The digital and analog baseband components of the xE922-3GR modules are presenting a good thermal

path to the top of their respective package. Therefore, thermal gap filler material has been added

between those components and the module shield to make use of this thermal path.

During Telit thermal measurements a heatsink with a thermal resistance of 6 K/W was mounted on the

shield of the module with conductive epoxy glue. The overall benefit was a 4°C decrease of the internal

temperature of the module.

In case the module is enclosed in a chassis, it is recommended to add thermal gap pad between the

shield and the enclosure to maintain a good thermal path. This is especially true if the module has to

operate in extreme temperature conditions (more than 60°C) for a power consumption of 3.3 Watts.



Figure 6 : heat sink mounted on xE922-3GR module – heat conduction on top and bottom of the housing



2.3 Software thermal management

xE922-3GR modules are based on Intel® Atom x3 chipset and need Intel firmware to deliver user

experience to the customer. The firmware delivered by Intel is embedding thermal management

software based on internal thermal sensors. The following sections are presenting a brief overview of

the behavior of this software and are indicating how to access the thermal sensors. This latest part could

help you during your thermal evaluation.

Software thermal management

Software and firmware algorithms allow mitigating excessive heat generated by the system components

to keep system temperatures within specified limits. It utilizes thermal sensing hardware to monitor

temperatures within the device. The results are tuning the performances and/or power control

mechanisms in system components to reduce heat dissipation.

Intel chipset firmware is provided with thermal management capabilities. This is part of the iTUX

application that will configure the hardware resources performances regarding the measurement results

coming from the thermal sensors available.

Figure 7 iTUX Intel Thermal Management overview

Thermal probes

Each modules provides seven thermal sensors.

There are six on-die sensors embedded in the Digital Baseband (DBB) and Analog RF+PMU:

● sensors for the physical core (Coretemp0, Coretemp1, Coretemp3)

● 1 sensor for the modem SPCU (Coretemp4)

● 1 sensor for the graphical GPU (Coretemp5).

● 1 sensor in the Analog RF+PMU (PMICtemp).

One sensor connected to a Thermistor in the module PCB (skin0/systemp).



Figure 8 : sensors locations in the module

The real-time value of the sensors could be monitored by reading the content of the following files (X=0..8):

/sys/class/thermal/thermal_zoneX/type

/sys/class/thermal/thermal_zoneX/temp

The scaling frequencies of the CPU could also be monitored by similar files (Y=0..3):

/sys/devices/system/cpu/cpuY/topology/core_id

/sys/devices/system/cpu/cpuY/cpufreq/scaling_cur_freq

/sys/devices/system/cpu/cpuY/cpufreq/cpuinfo_cur_freq

The following script is used to monitor the internal sensors. It needs to be uploaded to the module filesystem (for instance in /data/test/) and it runs using the sh and nohup shell commands.

#!/bin/bash header="%s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s %s\n" printf "$header" "scan" "," "coretemp0" "," "coretemp1" "," "coretemp3" "," "coretemp4" "," "coretemp5" "," "bat" "," "pmictemp" "," “battemp " "," “systemp" "," "cpufrequency0" "," "cpufrequency1" "," "cpufrequency2" "," "cpufrequency3" >/data/test/thermaltest.txt SCAN=0; while true; do THERMAL_0=$(</sys/class/thermal/thermal_zone0/temp) THERMAL_1=$(</sys/class/thermal/thermal_zone1/temp) THERMAL_2=$(</sys/class/thermal/thermal_zone2/temp) THERMAL_3=$(</sys/class/thermal/thermal_zone3/temp) THERMAL_4=$(</sys/class/thermal/thermal_zone4/temp) THERMAL_5=$(</sys/class/thermal/thermal_zone5/temp) THERMAL_6=$(</sys/class/thermal/thermal_zone6/temp) THERMAL_7=$(</sys/class/thermal/thermal_zone7/temp) THERMAL_8=$(</sys/class/thermal/thermal_zone8/temp) FREQ_0=$(</sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq) FREQ_1=$(</sys/devices/system/cpu/cpu1/cpufreq/scaling_cur_freq) FREQ_2=$(</sys/devices/system/cpu/cpu2/cpufreq/scaling_cur_freq) FREQ_3=$(</sys/devices/system/cpu/cpu3/cpufreq/scaling_cur_freq)



echo $SCAN, $THERMAL_0, $THERMAL_1, $THERMAL_2, $THERMAL_3, $THERMAL_4, $THERMAL_5, $THERMAL_6, $THERMAL_7, $((FREQ_0/1000)), $((FREQ_1/1000)), $((FREQ_2/1000)), $((FREQ_3/1000)) sleep 1; ((SCAN++)) done >>/data/test/thermaltest.txt

During prototyping of the final application, it is recommended to monitor the

skin0/systemp temperature. This value must never exceed 90°C in the worst

condition. This is not part of the iTUX software.

Throttling configuration

The digital Baseband and the analog RF+PMU dies temperature are constantly monitored by the

firmware and are already configured to shut-down the module if the measured temperature is too close

to their maximum junction temperature. The table below is describing the throttling behavior regarding

the readings of the thermal sensors.

Zone Throttling behavior

Normal Warning Alert Critical

CPU (coretemp0) < 65 °C 65 to 90 °C 90 to 105 °C > 110 °C

1160 MHz 900 MHz 728 MHz Shut down

GPU (coretemp5) < 85 °C 85 to 95 °C 95 to 105 °C > 110 °C

600 MHz 416 MHz 312 MHz 208 MHz

skin0 / System < 85 °C 85 to 95 °C 95 to 105 °C > 110 °C

1160 MHz 900 MHz 728 MHz 416 MHz

Table 2 : default throttling configuration



3 DOCUMENT HISTORY

Revision Date Changes

0 2016-10-21 First issue

0.1 2016-11-03 Minor typo fixes

Mod. 0809 2015-02 Rev.6