Sierra Wireless AirPrime XA1110 Guide

AirPrime XA1110 and XM1110
Hardware Design Guide
41111116
Rev 3.0

Hardware Design Guide
Rev 3.0 Aug.19 2 41111116
Important
Notice
Due to the nature of wireless communications, transmission and reception of data
can never be guaranteed. Data may be delayed, corrupted (i.e., have errors) or be
totally lost. Although significant delays or losses of data are rare when wireless
devices such as the Sierra Wireless modem are used in a normal manner with a
well-constructed network, the Sierra Wireless modem should not be used in
situations where failure to transmit or receive data could result in damage of any
kind to the user or any other party, including but not limited to personal injury,
death, or loss of property. Sierra Wireless accepts no responsibility for damages
of any kind resulting from delays or errors in data transmitted or received using
the Sierra Wireless modem, or for failure of the Sierra Wireless modem to
transmit or receive such data.
Safety and
Hazards
Do not operate the Sierra Wireless modem in areas where blasting is in progress,
where explosive atmospheres may be present, near medical equipment, near life
support equipment, or any equipment which may be susceptible to any form of
radio interference. In such areas, the Sierra Wireless modem MUST BE
POWERED OFF. The Sierra Wireless modem can transmit signals that could
interfere with this equipment.
Do not operate the Sierra Wireless modem in any aircraft, whether the aircraft is
on the ground or in flight. In aircraft, the Sierra Wireless modem MUST BE
POWERED OFF. When operating, the Sierra Wireless modem can transmit
signals that could interfere with various onboard systems.
Note: Some airlines may permit the use of cellular phones while the aircraft is on the
ground and the door is open. Sierra Wireless modems may be used at this time.
The driver or operator of any vehicle should not operate the Sierra Wireless
modem while in control of a vehicle. Doing so will detract from the driver or
operator's control and operation of that vehicle. In some states and provinces,
operating such communications devices while in control of a vehicle is an offence.
Limitation of
Liability
The information in this manual is subject to change without notice and does not
represent a commitment on the part of Sierra Wireless. SIERRA WIRELESS AND
ITS AFFILIATES SPECIFICALLY DISCLAIM LIABILITY FOR ANY AND ALL
DIRECT, INDIRECT, SPECIAL, GENERAL, INCIDENTAL, CONSEQUENTIAL,
PUNITIVE OR EXEMPLARY DAMAGES INCLUDING, BUT NOT LIMITED TO,
LOSS OF PROFITS OR REVENUE OR ANTICIPATED PROFITS OR REVENUE
ARISING OUT OF THE USE OR INABILITY TO USE ANY SIERRA WIRELESS
PRODUCT, EVEN IF SIERRA WIRELESS AND/OR ITS AFFILIATES HAS BEEN
ADVISED OF THE POSSIBILITY OF SUCH DAMAGES OR THEY ARE
FORESEEABLE OR FOR CLAIMS BY ANY THIRD PARTY.
Notwithstanding the foregoing, in no event shall Sierra Wireless and/or its
affiliates aggregate liability arising under or in connection with the Sierra Wireless
product, regardless of the number of events, occurrences, or claims giving rise to
liability, be in excess of the price paid by the purchaser for the Sierra Wireless
product.

Preface
Rev 3.0 Aug.19 3 41111116
Patents This product may contain technology developed by or for Sierra Wireless Inc. This
product includes technology licensed from QUALCOMM®. This product is
manufactured or sold by Sierra Wireless Inc. or its affiliates under one or more
patents licensed from MMP Portfolio Licensing.
Copyright © 2019 Sierra Wireless. All rights reserved.
Trademarks Sierra Wireless®, AirPrime®, AirLink®, AirVantage®and the Sierra Wireless logo
are registered trademarks of Sierra Wireless.
Windows®and Windows Vista®are registered trademarks of Microsoft
Corporation.
Macintosh®and Mac OS X®are registered trademarks of Apple Inc., registered in
the U.S. and other countries.
QUALCOMM®is a registered trademark of QUALCOMM Incorporated. Used
under license.
Other trademarks are the property of their respective owners.
Contact
Information
Revision
History
Sales information and technical
support, including warranty and returns
Web: sierrawireless.com/company/contact-us/
Global toll-free number: 1-877-687-7795
6:00 am to 5:00 pm PST
Corporate and product information Web: sierrawireless.com
Revision
number
Release date Changes
1June 23, 2017 Initial draft in SWI template.
2January 19, 2018 Updates throughout, changed title.
3.0 August 13, 2019 Removed obsolete module variants.

Rev 3.0 Aug.19 4 41111116
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Precautions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
General Rules for Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Circuit Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
VBACKUP Backup Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
UART / I2C/ SPI Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Antenna Compliance Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1PPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.8V Boost to 3.3V Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Layout Guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Layout Underneath the GNSS Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Keep XA1110 Far Away from High Profile or Metal-Canned Components . . . . . 19
Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Trace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Ground Segmentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Ground Plane for XA1110 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Thermal Profile for SMD Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SMT Reflow Soldering Temperature Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
SMT Solder Mask. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Manual Soldering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
How to Check the Working Status of the GPS Module . . . . . . . . . . . . . . . . . . . . . . . 24
Super Capacitor Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
About Super Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
How to Calculate the Backup Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
50 Ω Antenna Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Contents
Rev 3.0 Aug.19 5 41111116
UART to RS232 Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
UART to USB Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
How to Efficiently Transfer 1PPS Through Extended Distances. . . . . . . . . . . . . . . 29
1pps Delay Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
The Delay Time Caused by the Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Calculating the Delay Time in Respect to the Communication Cable Length . . . . . . 31
Waveform Rising Time Caused by OP-amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Recommended OP-amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Voltage Degradation of Communication Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Reflow Soldering Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Other Cautionary Notes on the Reflow-Soldering Process . . . . . . . . . . . . . . . . . . . . 35
Manual Soldering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Soldering Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Rev 3.0 Aug.19 6 41111116
1
1: Introduction
This document provides design guidelines for the following modules:
•Stand Alone GNSS module XM1110
Figure 1-1: XM1110 Multi-GNSS Module
•Integrated Patch Antenna Module: XA1110
Figure 1-2: XA1110
Precautions
Please read carefully before you start
If you use the GNSS receiver inside buildings, tunnels, or beside any huge objects,
the GNSS signals might be cut-off or weakened. Please do not assume the receiver
has malfunctioned.
This document provides the necessary guidelines for a successful system design
using GNSS modules. For detailed module specifications, please refer to the
corresponding datasheet of the GNSS module.
The GNSS module is an electrostatic sensitive device, please DO NOT touch the
GPS module directly. Follow ESD safety rules when handling.
When using the device for the first time, it is strongly recommended that you test the
device outdoors with open sky for at least 10 to 15 minutes to ensure that full
ephemeris data is received.

Rev 3.0 Aug.19 7 41111116
2
2: General Rules for Design
This section provides rules to obtain the best performance when using the GNSS
module.
Circuit Design
Power Supply
A clean and stable power supply is required for the GNSS modules to perform
optimally. An unstable power source will significantly impact GNSS performance. To
achieve high-quality performance, the VCC ripple must be controlled under 50mVpp.
Additional considerations to stabilize power supply include:
1. Adding a ferrite bead, power choke, or low pass filter for power noise reduction.
2. Adding a linear regulator (LDO) is rather than a switched DC/DC power supplier
in the ripple.
3. Using enough decoupling capacitors with the VCC for stable voltage.
Figure 2-1: Power Design for the GNSS Module
VBACKUP Backup Battery
The GNSS module has a built-in charging circuit which charges the rechargeable coin
battery.
It’s recommended that the module be provided with backup power (e.g. Li-Ion
rechargeable coin battery, super capacitor). See Figure 2-2 for a reference design.
For information on the super capacitor reference design, please refer to Super
Capacitor Design.
Backup power is needed to maintain RTC operation and retain Ephemeris data in
flash memory which helps the module get quicker TTFF and acquire PVT (Position,
Velocity, Time) information.

Hardware Design Guide
Rev 3.0 Aug.19 8 41111116
If VBACKUP isn’t connected to any coin battery, the GNSS module will execute a
cold start each time it’s restarted.
Figure 2-2: Rechargeable coin battery with VBACKUP
UART / I2C/ SPI Serial Interface
UART 0 (RX/TX)
1. UART is the TTL level interface that carries the baud rate ranging from 4800
bps to 115200 bps.
2. Placing a damping resistor on the RX and TX of the GNSS module could limit
the interference from the host MCU or high speed digital logics. Fine tuning
the damping resistor is required to efficiently suppress interference. The
damping resistor is a wire-wound component and may function as a choke
coil.
3. Don’t connect diode(s) to RX/TX as it will decrease the signal driving
capability which might adversely affect the RX/TX signal level. In some cases
no data output will occur.
4. If RS232 logic-level is needed, a level shifter should be used. For more infor-
mation please refer to UART to RS232 Interface.
5. If USB logic-level is needed please refer to the UART to USB Interface design
guidelines.
I2C (SCL/SDA)
1. The I2C interface is usually connected to external devices. MT3333 supports
only slave mode (default slave address is 0x10). MT3333 has 256 bytes of
URAM mode and an 8-byte FIFO mode for transmitting and receiving data.
The bit rate is up to 400 kb/s for fast mode. In addition, MT3333 supports a
manual or automatic indicator for data transfer in the slave mode. Device
addresses in slave mode are programmable.
2. A pull-up resistor must be added for the I2C bus:

General Rules for Design
Rev 3.0 Aug.19 9 41111116
Figure 2-3: Addition of Pull-up Resistor
SPI (CS/CLK/MISO/MOSI)
1. The serial peripheral interface port manages the communication between the
digital BB and external devices. The MT3333 supports only slave mode. The
slave has a 4 byte-register mode or URAM mode. In URAM mode, the size of
the transmitted and received data is 256 bytes. The clock phase and clock
polarity are selectable. The MT3333 supports a manual or automatic indicator
for data transfer in slave mode. The bit rate is up to 700kb/s.
Antenna Compliance Design
The GNSS antenna is the receiving part of the device that acquires weak GNSS
signals from the sky. A common solution is to use a ceramic patch antenna
because of its small form factor and low cost. There are two types of antennas:
passive and active.
A passive antenna, is a standalone component without a signal amplifier such as
an LNA. Patch antennas and chip antennas are the most commonly used passive
antennas with GNSS modules. When using an external passive antenna, ensure
that it is correctly fine-tuned for the specific module to ensure best possible signal
strength.
An Active antenna is a standalone external antenna that comes with an integrated
LNA. These antennas provide higher gain and better performance than that of a
passive antenna. An example of an active antenna includes Patch Antenna with
RF Cable and Integrated LNA.
Antenna should be chosen according to radiation efficiency, radiation pattern,
gain, bandwidth, form factor, and cost. Make sure the ground plane is sufficient
for the antenna to ensure best performance.

Hardware Design Guide
Rev 3.0 Aug.19 10 41111116
Designing an External Passive Patch Antenna with
GNSS module
1. In general, a 50Ω patch antenna will work well with the GNSS module. The
antenna can be connected to the Antenna IN pin with a 50Ω impedance
trace.
2. Please keep the patch antenna far away from noise sources such as the
switching power supply and high speed digital logic and radar wave guide.
3. The 50Ω trace should be kept as short as possible to reduce the chance of
picking up noise from the air and PCB. A simple direct-line trace is
recommended.
4. If needed, a matching circuit can be placed between the patch antenna and
the GNSS module. The matching circuit design should be discussed with the
module and patch antenna manufacturer.
5. For 50Ω matching, please refer to 50 Ω Antenna Matching.
Figure 2-4: PCB Trace Design for Antenna Impedance Matching
Selecting an Active Antenna Architecture for the
GNSS Module
An external active antenna requires DC power in order to work properly. A typical
method is to feed DC into the RF trace. The external antenna then extracts the
DC from the RF trace. Thus the RF trace transports both the RF signal and DC
power. An RF choke coil couples the DC power to the RF trace to perform this
method.
Support two architectures for this as shown below in Figure 2-5 and Figure 2-6.
•Mode1: The power supply needs to be externally provided and is connected
directly to the external antenna via a choke coil. See Table 2-1.
Note: Choke Coil for reference: LQG15HS33NJ02D (Murata)
•Mode2: The power supply for the external antenna needs to be externally fed
into the module from the VCC pin directly and the antenna connected to the
EX_ANT pin.

General Rules for Design
Rev 3.0 Aug.19 11 41111116
Figure 2-5: Mode 1 (External Choke Coil)
Figure 2-6: Mode 2 (Internal Choke Coil)
Table 2-1: Modes
XM1110 XA1110
Mode 1 (via the VANT)
(External Choke Coil) 
Mode 2 (from the VCC)
(Internal Choke Coil) 

Hardware Design Guide
Rev 3.0 Aug.19 12 41111116
Designing a Chip Antenna with GNSS Module
It’s recommended to consult chip antenna vendors for more specific design
guidelines. Below references are for chip antennas from Pulse and Unictron.
1. Pulse Antenna
Figure 2-7: Pulse Schematic Design
Figure 2-8: Pulse PCB Layout
Check antenna datasheet before tuning RF to match the component footprint
(such as: C27, C28). You can base this on PCB size and housing to tune for an
optimal value and meet the GNSS’s frequency to get good reception.
Pulse web site:
www.pulseeng.com/antennas
Note: C27, C28’s values are still based on your actual trace to tune it.
2. Unictron Antenna

General Rules for Design
Rev 3.0 Aug.19 13 41111116
Figure 2-9: Unictron Schematic
Figure 2-10: Unictron PCB
Check the antenna datasheet before tuning RF to match the component footprint
(such as: C26, C27, C28, C29, C30). You can tune based on PCB size and
housing to tune for an optimal value in order to meet the GNSS’s frequency and
for good reception.
Unictron web site: http://www.unictron.com/index/
Note: The values for C26,C27,C28,C29, and C30 are tuned based on your trace.
External Antenna of Specification
When selecting your external antenna, refer to the specification shown in
Table 2-2 and Table 2-3 below.
Table 2-2: GPS/GLONASS External Antenna
Characteristic Specification
Polarization Right-hand circular polarized
Frequency Received 1.575GHz~1.615GHz

Hardware Design Guide
Rev 3.0 Aug.19 14 41111116
1PPS
1PPS signal is an output pulse signal used for timing applications. Its electrical
characteristics are:
•Low Voltage level: 0~0.4V
•High Voltage level: 2.8~3.1V
•Period: 1s
•Accuracy (jitter):±20ns
•100ms pulse width duration
Power Supply 3.3V
DC Current 5mA<IDC<11mA at 3.3V
Total Gain 27±3dB
Output VSWR 2.0
Impendence 50Ω
Noise Figure 2dB
Table 2-3: Beidou/GPS External Antenna
Characteristic Specification
Polarization Right-hand circular polarized
Frequency Received 1.561GHz~1.575GHz
Power Supply 3.3V
DC Current 3mA<IDC<30mA at 3.3V
Total Gain 27±1dB
Output VSWR 2.0
Impendence 50Ω
Noise Figure 1.5dB
Table 2-2: GPS/GLONASS External Antenna (Continued)
Characteristic Specification

General Rules for Design
Rev 3.0 Aug.19 15 41111116
Figure 2-11: 1PPS signal and its pulse width with 100ms duration
Free run 1PPS Output Before 3D_FIX
The Sierra Wireless standard GNSS module outputs 1PPS signal after the
module obtains a 3D_FIX. This is a factory default setting.
Cable Delay Compensation
In some cases, a long-distance connection (~300m) may be needed. For a timing
application, the cable length is critical. For more information on 1PPS signal
transmission delay please refer to How to Efficiently Transfer 1PPS Through
Extended Distances.
LED Indicator for 1PPS Signal
For 1PPS LED indication, you may connect an LED indicator with a 330ohm
resistor in series.
Figure 2-12: 1PPS Signal Design for IO

Hardware Design Guide
Rev 3.0 Aug.19 16 41111116
1.8V Boost to 3.3V Application
If you want to use the 3.3V’s GNSS module in a 1.8V system there are two
considerations: power supply translation and signal level shift. For power supply
translation, you can use a boost circuit which can boost 1.8V to 3.3V (refer to
Figure 2-13 below).
TPS61097A-33 is the TI’s boost IC which can support boost functionality. In its
application C1 and C2 need to use 10uF and L1 is 10uH. It can support
approximately 100mA of output. For information about the capacitor and
inductor’s placement, refer to the application note on the TI web site:
http://www.ti.com/lit/ds/symlink/tps61097a-33.pdf.
Figure 2-13: Application Schematic for TI Boost IC
Figure 2-14: Output Voltage vs Output Current

General Rules for Design
Rev 3.0 Aug.19 17 41111116
For signal level shift, when your host system is 1.8V and the Sierra Wireless
module is 3.3V, the host system can control the Sierra Wireless module by using
a signal level shift circuit (refer to Figure 2-15 below). R1 to R4’s values are
default values. In your design, you can adjust their values to achieve control. The
2N7002L can select low RDS(On) to reduce power consumption through a
voltage drop.
Figure 2-15: Signal Level Shift Circuit
Layout Guidelines
Please follow the layout guidelines during the design process.
Layout Underneath the GNSS Module
In general, GNSS modules have high receiving sensitivity at around -165dBm.
During hardware integration, try to avoid noise or harmonics in the following
bands to prevent unnecessary reception degradation:
•Beidou 1561.098MHz ±2.046MHz and GPS 1572.42MHz±2MHz
•GLONASS 1598.0625~1605.375MHz
Modern GNSS positioning products include many components such as an LCD
screen, MCU, high speed digital signal (access memory card), and an RF system
(i.e. Cellular module, BT, Wi-Fi, DVB-T). Keep these components away from the
GNSS module to avoid noise interference, otherwise it may result in poor GNSS
RF reception.
For XM1110
Don’t leave any trace or mark underneath the GNSS module as indicated by the
circled area in figure Figure 2-16 below.

Hardware Design Guide
Rev 3.0 Aug.19 18 41111116
Figure 2-16: GNSS Module with a Clean GND Plane
Don’t place any trace such as I2C (SCL/SDA), SPI (CLK/MISO/MOSI), UART (TX/
RX) underneath the GNSS module, otherwise it will cause a sensitivity decrease.
For XA1110
To avoid the interference, place many vias on the two sides of the RF trace which
goes from the module to the SMA/RF connector on your system PCB as
illustrated in Figure 2-17 below.
Don’t place any high-speed traces such as I2C (SCL/SDA), SPI (CLK/MISO/
MOSI), UART (TX/RX) underneath the GNSS module.
Figure 2-17: GNSS Antenna Module with Clear GND Plane

General Rules for Design
Rev 3.0 Aug.19 19 41111116
Keep XA1110 Far Away from High Profile or
Metal-Canned Components
It’s good practice to place the GNSS module far away from any high-profile
components especially those enclosed in metal cases such as the E-CAP, coin
battery, and Pin Header. The antenna field pattern can be affected, and pattern
distortion can occur. At worst, this will decrease the GNSS signal up to ~10dB.
Figure 2-18: First Example of Bad and Good GNSS Module Placement
Figure 2-19: Second Example of Bad and Good GNSS Module Placement
Figure 2-20: Third Example of Bad and Good GNSS Module Placement

Hardware Design Guide
Rev 3.0 Aug.19 20 41111116
Figure 2-21: Example of Bad GPS Module Placement (Patch Antenna Close to a High-Profile Metal
Case Component) and Good Placement
Placement
•Place the decoupling capacitors for the VCC close to the GNSS module.
•Place the damping resistors for TX/RX close to GNSS module.
Do not place the GNSS module:
•in proximity to high-speed digital processing circuitry
•in proximity to high-current switching power circuitry
•in proximity to clock sources circuitry
Trace
1. The USB differential signals should be traced closely and be of equal length
for better noise immunity and minimum radiation.
2. Apply a 50 ohm impedance RF trace for correct impedance matching.
3. Any right angle turn in trace routing should be done with two 135 degree
turns or an arc turn.
Figure 2-22: Examples of turns in trace routing
It is better to have an independent trace of the power source for all components: