Page 1
Abstract
This document describes the features and specifications of u-blox LEA-M8S and LEA-M8T modules.
www.u-blox.com
UBX-15030060 - R06
LEA-M8S / LEA-M8T
u-blox M8 concurrent GNSS modules
Hardware integration manual
Page 2
LEA-M8S / LEA-M8T - Hardware integration manual
Title
LEA-M8S / LEA-M8T
Subtitle
u-blox M8 concurrent GNSS modules
Document type
Hardware integration manual
Document number
UBX-15030060
Revision and date
R06
5-May-2020
Document status
Production information
Product status
Corresponding content status
In Development /
Prototype
Objective Specification
Target values. Revised and supplementary data will be published later.
Engineering Sample
Advance Information
Data based on early testing. Revised and supplementary data will be published later.
Initial Production
Early Production Information
Data from product verification. Revised and supplementary data may be published later.
Mass Production /
End of Life
Production Information
Document contains the final product specification.
Product name
Type number
Firmware version
PCN reference
LEA-M8S
LEA-M8S-0-10
ROM SPG 3.01
UBX-16012752
LEA-M8T
LEA-M8T-0-10
Flash FW 3.01 TIM 1.10
UBX-16004907
LEA-M8T
LEA-M8T-1-00
Flash FW 3.01 TIM 1.11
u-blox or third parties may hold intellectual property rights in the products, names, logos and designs included in this
document. Copying, reproduction, modification or disclosure to third parties of this document or any part thereof is only
permitted with the express written permission of u-blox.
The information contained herein is provided “as is” and u-blox assumes no liability for its use. No warranty, either express or
implied, is given, including but not limited to, with respect to the accuracy, correctness, reliability and fitness for a particular
purpose of the information. This document may be revised by u-blox at any time without notice. For the most recent
documents, visit www.u-blox.com.
Copyright © u-blox AG.
Document information
This document applies to the following products:
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Contents
Document information ................................................................................................................................ 2
Contents .......................................................................................................................................................... 3
1 Hardware description ........................................................................................................................... 5
1.1 Overview ........................................................................................................................................................ 5
1.2 Configuration ............................................................................................................................................... 5
1.3 Connecting power ....................................................................................................................................... 5
1.3.1 VCC: Main supply voltage ................................................................................................................. 5
1.3.2 V_BCKP: Backup supply voltage ...................................................................................................... 5
1.3.3 VDD_USB: USB interface power supply ......................................................................................... 6
1.3.4 VCC_RF: Output voltage RF section ............................................................................................... 6
1.3.5 V_ANT: Antenna supply .................................................................................................................... 6
1.4 Interfaces ...................................................................................................................................................... 6
1.4.1 UART ..................................................................................................................................................... 6
1.4.2 USB ........................................................................................................................................................ 6
1.4.3 Display data channel (DDC) .............................................................................................................. 7
1.4.4 SPI (LEA-M8T only) ............................................................................................................................ 7
1.4.5 TX_READY ............................................................................................................................................ 8
1.5 I/O pins ........................................................................................................................................................... 8
1.5.1 RESET_N: Reset .................................................................................................................................. 8
1.5.2 EXTINT: External interrupt ............................................................................................................... 8
1.5.3 SAFEBOOT_N ...................................................................................................................................... 8
1.5.4 D_SEL: Interface select (LEA-M8T only) ........................................................................................ 9
1.5.5 Antenna open circuit detection (ANT_DET_N) ............................................................................. 9
1.5.6 TIMEPULSE.......................................................................................................................................... 9
1.5.7 TIMEPULSE 2 (LEA-M8T only) ........................................................................................................ 9
1.6 Electromagnetic interference on I/O lines ............................................................................................. 9
2 Design ..................................................................................................................................................... 11
2.1 Pin description ...........................................................................................................................................11
2.1.1 Pin name changes.............................................................................................................................12
2.2 Minimal design...........................................................................................................................................13
2.3 Footprint and paste mask .......................................................................................................................13
2.4 Antenna .......................................................................................................................................................14
2.4.1 Antenna design with passive antenna .........................................................................................14
2.4.2 Active antenna design .....................................................................................................................15
2.4.3 Power and short detection antenna supervisor .........................................................................17
2.4.4 Power, short and open detection antenna supervisor ..............................................................18
2.5 Layout design-in: Thermal management .............................................................................................19
3 Migration to u-blox M8 modules .................................................................................................... 20
3.1 Migrating u-blox 6 designs to u-blox M8 module ...............................................................................20
3.2 Hardware migration LEA-6N -> LEA-M8S ...........................................................................................20
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3.3 Hardware migration LEA-6T -> LEA-M8T ...........................................................................................21
3.4 Software migration ...................................................................................................................................21
4 Product handling ................................................................................................................................. 22
4.1 Packaging, shipping, storage and moisture preconditioning ..........................................................22
4.2 Soldering .....................................................................................................................................................22
4.3 EOS/ESD/EMI precautions ......................................................................................................................25
4.4 Applications with cellular modules ........................................................................................................28
Appendix ....................................................................................................................................................... 30
A Glossary ................................................................................................................................................. 30
B Recommended parts ......................................................................................................................... 30
Related documents ................................................................................................................................... 32
Revision history .......................................................................................................................................... 32
Contact .......................................................................................................................................................... 33
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1 Hardware description
1.1 Overview
LEA-M8S and LEA-M8T are concurrent GNSS positioning modules featuring the high performance
u-blox M8 positioning engine. They are easy to integrate and combine exceptional positioning
performance with highly flexible power, design, and connectivity options. SMT pads allow fully
automated assembly with standard pick-and-place and reflow-soldering equipment for cost-efficient,
high-volume production enabling short time-to-market.
☞ For specific product features, see LEA-M8S Data sheet [1] and NEO / LEA-M8T Data sheet [2].
☞ To determine which u-blox product best meets your needs, see the product selector tables on the
u-blox website.
1.2 Configuration
The configuration settings can be modified using UBX protocol configuration messages, for more
information see the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification [3]. The
modified settings remain effective until power-down or reset. If these settings have been stored in
Battery Backed RAM (BBR), the modified configuration will be retained, as long as the backup battery
supply is not interrupted.
1.3 Connecting power
The LEA-M8S and LEA-M8T positioning modules have up to three power supply pins: VCC, V_BCKP
and VDD_USB.
1.3.1 VCC: Main supply voltage
The VCC pin provides the main supply voltage. During operation, the current drawn by the module can
vary by some orders of magnitude, especially if enabling low-power operation modes. For this reason,
it is important that the supply circuitry is able to support the peak power for a short time (see the
LEA-M8S Data sheet [1] and the NEO / LEA-M8T Data sheet Error! Reference source not found. for
etailed specifications).
☞ When switching from backup mode to normal operation or at start-up, the LEA-M8S and LEA-
M8T modules must charge the internal capacitors in the core domain. In certain situations, this
can result in a significant current draw. For low-power applications using power save and backup
modes, it is important that the power supply or low ESR capacitors at the module input can deliver
this current/charge.
☞ Use a proper GND concept. Do not use any resistors or coils in the power line.
1.3.2 V_BCKP: Backup supply voltage
If the module supply has a power failure, the V_BCKP pin supplies the real-time clock (RTC) and
battery-backed RAM (BBR). Use of valid time and the GNSS orbit data at start-up will improve the
GNSS performance, that is, it enables hot and warm starts. If no backup battery is connected, the
module performs a cold start at power-up.
☞ Avoid high resistance on the V_BCKP line: During the switch from main supply to backup supply,
a short current adjustment peak can cause high voltage drop on the pin with possible
malfunctions.
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☞ If no backup supply voltage is available, connect the V_BCKP pin to VCC.
☞ As long as the LEA-M8S and LEA-M8T modules are supplied via the VCC, the backup battery is
disconnected from the RTC and the BBR to avoid unnecessary battery drain (see Figure 1). In this
case, VCC supplies power to the RTC and BBR.
Figure 1: Backup battery and voltage (for exact pin orientation, see the LEA-M8S Data sheet [1] and the NEO/LEA-M8T Data
sheet [2]
1.3.3 VDD_USB: USB interface power supply
VDD_USB supplies the USB interface. If the USB interface is not used, the VDD_USB pin must be
connected to GND. For more information about correctly handling the VDD_USB pin, see section 1.4.
1.3.4 VCC_RF: Output voltage RF section
The VCC_RF pin can supply an active antenna or external LNA. For more information, see section 2.4.
1.3.5 V_ANT: Antenna supply
The V_ANT pin is available to provide antenna bias voltage to supply an optional external active
antenna. For more information, see section 2.4.
☞ If not used, connect the V_ANT pin to GND.
1.4 Interfaces
1.4.1 UART
The LEA-M8S and LEA-M8T positioning modules include a universal asynchronous receiver
transmitter (UART) serial interface RXD/TXD, which supports configurable baud rates. The baud
rates supported are specified in the LEA-M8S Data sheet [1] and the NEO / LEA-M8T Data sheet [2]
The signal output and input levels are 0 V to VCC. An interface based on RS232 standard levels
(+/- 12 V) can be implemented using level shifters such as Maxim MAX3232. Hardware handshake
signals and synchronous operation are not supported.
1.4.2 USB
A USB version 2.0 FS (full speed, 12 Mb/s) compatible interface is available for communication as an
alternative to the UART. The USB_DP integrates a pull-up resistor to signal a full-speed device to the
host. The VDD_USB pin supplies the USB interface.
u-blox provides Microsoft® certified USB drivers for Windows Vista, Windows 7, Windows 8 and
Windows 10 operating systems. These drivers are available at our website at www.u-blox.com.
USB external components
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Module
VDD_USB
LDO
VDD_USB
R4
USB_DP
USB_DM
R5
C24 C23
D2
VBUS
DP
DM
GND
USB
Device Connector
U1
EN R11
EN
Name
Component
Function
Comments
U1
LDO
Regulates VBUS (4.4 … 5.25 V) down
to a voltage of 3.3 V.
Almost no current requirement (~1 mA).
C23,
C24
Capacitors
Required according to the specification of LDO U1.
D2
Protection diodes
Protect circuit from overvoltage /
ESD when connecting.
Use low capacitance ESD protection such as ST
Microelectronics USBLC6-2.
R4, R5
Serial termination
resistors
Establish a full-speed driver
impedance of 28 … 44
A value of 27 is recommended.
R11
Resistor
100 k is recommended for USB self-powered setup.
For bus-powered setup, R11 can be ignored.
The USB interface requires some external components to implement the physical characteristics
required by the USB 2.0 specification. These external components are shown in Figure 2 and listed in
Table 1. To comply with USB specifications, VBUS must be connected through an LDO (U1) to pin
VDD_USB on the module.
The USB device is self-powered, the power supply (VCC) can be turned off and the digital block is not
powered. In this case, since VBUS is still available, the USB host still receives the signal indicating that
the device is present and ready to communicate. This should be avoided by disabling the LDO (U1)
using the enable signal (EN) of the VCC-LDO or the output of a voltage supervisor. Depending on the
characteristics of the LDO (U1), it is recommended to add a pull-down resistor (R11) at its output to
ensure VDD_USB is not floating if the LDO (U1) is disabled or the USB cable is not connected, that is,
VBUS is not supplied.
☞ USB bus powered is not supported.
Figure 2: USB interface
Table 1: Summary of USB external components
1.4.3 Display data channel (DDC)
An I2C-compatible display data channel (DDC) interface is available for serial communication with an
external host CPU. The interface only supports operation in slave mode (master mode is not
supported). The DDC protocol and electrical interface are fully compatible with the fast mode of the
I2C industry standard. DDC pins SDA and SCL have internal pull-up resistors.
For more information about the DDC implementation, see the u-blox 8 / u-blox M8 Receiver
Description Including Protocol Specification [3]. For bandwidth information, see the LEA-M8S Data
sheet [1] and the NEO / LEA-M8T Data sheet [2]. For timing parameters, consult the I2C-bus
specification [6].
☞ The u-blox M8 DDC interface supports serial communication with most u-blox cellular modules.
See the specification of the applicable cellular module to confirm compatibility.
1.4.4 SPI (LEA-M8T only)
An SPI interface is available for communication to a host CPU.
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☞ SPI is not available in the default configuration because its pins are shared with the UART and DDC
interfaces. The SPI interface can be enabled by connecting D_SEL to ground. For speed and clock
frequency, see the NEO / LEA-M8T Data sheet [2].
1.4.5 TX_READY
The TX_READY function is used to indicate when the receiver has data to transmit. A listener can wait
on the TX_READY signal instead of polling the DDC or SPI interfaces. The UBX-CFG-PRT message lets
you configure the polarity and the number of bytes in the buffer before the TX_READY signal goes
active. The TX_READY function can be mapped to TXD (PIO 06). The TX_READY function is disabled
by default.
☞ The TX_READY functionality can be enabled and configured by AT commands sent to the u-blox
cellular module supporting the feature. For more information, see the GPS Implementation and
Aiding Features in u-blox Wireless Modules [7].
1.5 I/O pins
1.5.1 RESET_N: Reset
Driving RESET_N low activates a hardware reset of the system. Use this pin only to reset the module.
Do not use RESET_N to turn the module on and off, since the reset state increases power
consumption. With LEA-M8S and LEA-M8T module RESET_N is an input only.
☞ The RTC time is also reset (but not BBR).
1.5.2 EXTINT: External interrupt
EXTINT0 and EXTINT1 are external interrupt pins with fixed input voltage thresholds with respect to
VCC (see the LEA-M8S Data sheet [1] and the NEO / LEA-M8T Data sheet [2] for more information).
They can be used for wake-up functions in power save mode and for aiding. Leave open if unused.
The EXTINT0 pin can also be configured as a generic PIO (PIO13).
The EXTINT1 pin can also be configured as an active antenna open circuit detection function
(ANT_DET_N). For further information see sections 1.5.5 and 2.4.4.
Power control
The power control feature allows overriding the automatic active/inactive cycle of power save mode.
The state of the receiver can be controlled through the EXTINT0 and EXTINT1 pin. The receiver can
also be forced OFF using EXTINT0 and EXTINT1 when power save mode is not active.
Frequency aiding
The EXTINT0 and EXTINT1 pins can be used to supply time or frequency aiding data to the receiver.
For time aiding, hardware time synchronization can be achieved by connecting an accurate time pulse
to the EXTINT0 pin.
Frequency aiding can be implemented by connecting a periodic rectangular signal with a frequency up
to 500 kHz and arbitrary duty cycle (low/high phase duration must not be shorter than 50 ns) to the
EXTINT0 pin. Provide the applied frequency value to the receiver using UBX messages.
1.5.3 SAFEBOOT_N
The SAFEBOOT_N pin is for future service, updates and reconfiguration.
☞ Do not pull low during reset.
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1.5.4 D_SEL: Interface select (LEA-M8T only)
The D_SEL pin selects the available interfaces. SPI cannot be used simultaneously with UART/DDC.
If open, UART and DDC are available. If pulled low, the SPI interface is available. See the NEO / LEAM8T Data sheet [2].
1.5.5 Antenna open circuit detection (ANT_DET_N)
ANT_DET_N on EXTINT1 PIO14 is an input pin used to report whether an external circuit has detected
an external antenna or not.
"low" = Antenna detected (antenna consumes current)
"high" = Antenna not detected (no current drawn). This functionality is by default disabled.
For more information, see section 2.4.4.
Antenna supervision is configurable using message UBX-CFG-ANT.
☞ Refer to the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification Error!
eference source not found. for information about further settings.
1.5.6 TIMEPULSE
A configurable time pulse signal is available on LEA-M8S and LEA-M8T. By default, the time pulse
signal is configured to one pulse per second. For more information, see the u-blox 8 / u-blox M8
Receiver Description Including Protocol Specification [3].
1.5.7 TIMEPULSE 2 (LEA-M8T only)
A configurable TIMEPULSE2 signal is available on LEA-M8T module only. For more information see
the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification [3].
1.6 Electromagnetic interference on I/O lines
Any I/O signal line with a length greater than approximately 3 mm can act as an antenna and may pick
up arbitrary RF signals, transferring them as noise into the GNSS receiver. This specifically applies to
unshielded lines, in which the corresponding GND layer is remote or missing entirely, and to lines close
to the edges of the printed circuit board.
If, for example, a cellular signal radiates into an unshielded high-impedance line, it is possible to
generate noise in the order of volts and not only distort receiver operation but also damage it
permanently. On the other hand, noise generated at the I/O pins will emit from unshielded I/O lines.
Receiver performance may be degraded if this noise is coupled to the GNSS antenna (see Figure 18).
To avoid interference by improperly shielded lines, it is recommended to use resistors (e.g. R>20 ),
ferrite beads (for example, BLM15HD102SN1) or inductors (for example, LQG15HS47NJ02) on the
I/O lines in series. Choose these components with care because they will also affect the signal rise
times.
Figure 3 shows an example of EMI protection measures on the RX/TX line using a ferrite bead. More
information can be found in section 4.3.
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Figure 3: EMI Precautions
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Function
Pin
No.
I/O
Description
Remarks
Power
VCC 6 I
Supply voltage
Provide clean and stable supply.
GND
7, 13, 14,
15, 17
-
Ground
Assure a good GND connection to all GND pins of
the module.
VCC_OUT
8 O Output voltage (VCC)
Leave open if not used.
V_BCKP
11 I Backup supply voltage
It is recommended to connect a backup supply
voltage to V_BCKP in order to enable warm and
hot start features on the positioning modules.
Otherwise, connect to VCC.
VDD_USB
24 I USB power supply
To use the USB interface connect this pin to 3.0 –
3.6 V.
If no USB serial port used connect to GND.
Antenna
RF_IN
16
I
GNSS signal input from
antenna
Use a controlled impedance transmission line of
50 to connect to RF_IN.
VCC_RF
18
O
Output voltage RF
section
Can be used to power external LNA or an external
active antenna (VCC_RF connected to V_ANT
with 10 ). The max power consumption of the
antenna must not exceed the data sheet
specification of the module. Leave open if not
used.
V_ANT
19 I Antenna bias voltage
Connect to GND (or leave open) if passive antenna
is used. If an active antenna is used, add a 10
resistor in front of V_ANT input to the antenna
bias voltage or VCC_RF.
EXTINT1
20 I Ext. interrupt
Ext. interrupt pin. Int. pull-up resistor to VCC. Can
be configured as open circuit detection
(ANT_DET_N). Leave open if not used.
UART
TXD 3
(LEA-M8S)
TXD / SPI MISO
(LEA-M8T)
O
TXD Serial port TXD
O
TXD
SPI MISO
Serial port TXD if D_SEL =1 (or open)
SPI MISO if D_SEL = 0
RXD 4
(LEA-M8S)
RXD / SPI MOSI
(LEA-M8T)
I
RXD Serial port if RXD
I
RXD
SPI MOSI
Serial port if RXD D_SEL =1 (or open)
SPI MOSI if D_SEL = 0
USB
USB_DM
25
I/O
USB I/O line
USB2.0 bidirectional communication pin. Leave
open if unused. For implementations, see section
1.4.
USB_DP
26
I/O
USB I/O line
System
RESET_N
10 I Hardware Reset
(Active Low)
Leave open if not used. Do not drive high.
TIMEPULSE
28 O Timepulse 1
Configurable timepulse 1 signal (one pulse per
second by default). Leave open if not used.
TP2/SAFEBOOT_
N
(LEA-M8T)
SAFEBOOT_N
(LEA-M8S)
12
I/O
Safeboot_N / Timepulse
2
Configurable timepulse signal. Must not be held
LO during start-up.
I/O
Safeboot_N
Must not be held LO during start-up.
EXTINT0 / PIO13
27
I /
(O)
Ext. interrupt / PIO13
Ext. interrupt pin. Int. pull-up resistor to VCC.
Leave open if unused. The pin can also be used as
a generic PIO (PIO13).
2 Design
2.1 Pin description
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Function
Pin
No.
I/O
Description
Remarks
SDA 1
(LEA-M8S)
SDA /SPI CS_N
(LEA-M8T)
I/O
SDA
DDC data
I/O
SDA
SPI CS_N
DDC data if D_SEL =1 (or open)
SPI chip select if D_SEL = 0
SCL 2
(LEA-M8S)
SCL / SPI CLK
(LEA-M8T)
I/O
SCL
DDC clock
I/O
SCL
SPI CLK
DDC clock if D_SEL =1 (or open)
SPI clock if D_SEL = 0
RESERVED 5
(LEA-M8S)
D_SEL
(LEA-M8T)
I
Reserved
Leave open
I
Interface select
D_SEL = 0 -> SPI, D_SEL =1 (or open) -> DDC
Reserved
9, 21, 22,
23
-
Reserved
Leave open
No
Previous name
New name
3
TxD (LEA-M8S)
TXD 3 TxD (LEA-M8T)
TXD / SPI MISO
4
RxD (LEA-M8S)
RXD
4
RxD (LEA-M8T)
RXD / SPI MOSI
12
Reserved (LEA-M8S)
SAFEBOOT_N
20
AADET_N
EXTINT1
Table 2: Pinout LEA-M8S / LEA-M8T
2.1.1 Pin name changes
Selected pin names have been updated to agree with a common naming convention across u-blox
modules. The pins have not changed their operation and are the same physical hardware but with
updated names. The table below lists the pins that have changed their name along with their old and
new names.
Table 3: Pin name changes
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2.2 Minimal design
This is a minimal setup for a GNSS receiver with a LEA-M8S and LEA-M8T module:
Passive antenna used
No backup battery
UART for communication
Figure 4: LEA-M8S / LEA-M8T passive antenna design
☞ For active antenna design, see section 2.4.
2.3 Footprint and paste mask
Figure 5 describes the footprint and provides recommendations for the paste mask for the LEA-M8S
and LEA-M8T modules. These are recommendations only and not specifications. Note that the
copper and solder masks have the same size and position.
To improve the wetting of the half vias, reduce the amount of solder paste under the module and
increase the volume outside of the module by defining the dimensions of the paste mask to form a Tshape (or equivalent) extending beyond the copper mask. For the stencil thickness, see Figure 6.
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17.0 mm [669 mil]
22.4 mm [881.9 mil]
1.0 mm
[39 mil]
0.8 mm
[31.5 mil]
2.45 mm
[96.5 mil]
1.1 mm
[43 mil]
3.0 mm
[118 mil]
2.15 mm
[84.5 mil]
0.8 mm
[31.5 mil]
Figure 5: LEA-M8S and LEA-M8T footprint
Figure 6: LEA-M8S and LEA-M8T paste mask
2.4 Antenna
☞ For exact pin orientation in any design, see the LEA-M8S Data sheet [1] and the NEO / LEA-M8T
Data sheet [2].
☞ For recommended parts, see Appendix B.
2.4.1 Antenna design with passive antenna
A design using a passive antenna requires more attention to the layout of the RF section. Typically, a
passive antenna is located near electronic components; therefore, take care to reduce electrical noise
that may interfere with the antenna performance. Passive antennas do not require a DC bias voltage
and can be directly connected to the RF input pin RF_IN. Sometimes they may also need a passive
matching network to match the impedance to 50 .
☞ Use an antenna that has sufficient bandwidth to receive all GNSS constellations. For
recommended parts, see Appendix B.
Minimal setup with a good patch antenna
Figure 7 shows a minimal setup for a design with a good GNSS patch antenna.
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Figure 7: Module design with passive antenna
Setup for best performance with passive antenna
Figure 8 shows a design using an external LNA to increase the sensitivity for best performance with
passive antenna.
Figure 8: Module design with passive antenna and an external LNA
The VCC_RF output can be used to supply the LNA with a filtered supply voltage.
☞ A standard GNSS LNA has enough bandwidth to amplify GPS / Galileo / GLONASS and BeiDou
signals.
2.4.2 Active antenna design
Active antennas have an integrated low-noise amplifier. Active antennas require a power supply that
will contribute to the total GNSS system power consumption budget with additional 5 to 20 mA
typically.
If the customers do not want to make use of the internal antenna supervisor and the supply voltage
of the LEA-M8S and LEA-M8T module matches the supply voltage of the antenna (for example, 3.0
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V), they can use the filtered supply voltage VCC_RF output to supply the antenna (see Figure 9). This
design is used for modules in combination with active antenna.
In case of different supply voltage, use a filtered external supply, see Figure 10.
Active antenna design using VCC_RF pin to supply the active antenna
Figure 9: Active antenna design, external supply from VCC_RF
Active antenna design powered from external supply
Figure 10 shows a design with a direct externally powered active antenna.
This circuit has to be used if the active antenna has a different supply voltage than the VCC_RF (for
example, if a 5 V active antenna is used).
Figure 10: Active antenna design, direct external supply
☞ In case VCC_RF voltage does not match with the antenna supply voltage, use a filtered external
supply as shown in Figure 10.
Antenna design with active antenna using antenna supervisor
An active antenna supervisor provides the means to check the antenna for open and short circuits
and to shut off the antenna supply if a short circuit is detected. The antenna supervisor is configured
using serial port UBX binary protocol message. Once enabled, the active antenna supervisor produces
status messages, reporting in NMEA and/or UBX binary protocol.
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Abbreviation
Description
AC
Active antenna control enabled
SD
Short circuit detection Enabled
OD
Open circuit detection enabled
PDoS
Short circuit power down logic enabled
SR
Automatic recovery from short state
The current active antenna status can be determined by polling the UBX-MON-HW monitor
command. If an antenna is connected, the initial state after power-up is “Active Antenna OK.”
The module firmware supports an active antenna supervisor circuit, which is connected to the
ANT_DET_N pin. For an example of an open circuit detection circuit, see Figure 13.
"high" = Antenna detected (antenna consumes current)
"low" = Antenna not detected (no current drawn)
Status reporting
At startup, and on every change of the antenna supervisor configuration, the LEA-M8S module will
output an NMEA ($GPTXT) or UBX (INF-NOTICE) message with the internal status of the antenna
supervisor (disabled, short detection only, enabled).
Table 4: Active antenna supervisor message on startup (UBX binary protocol)
☞ To activate the antenna supervisor, use the UBX-CFG-ANT message. For further information,
refer to the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification [3].
Similar to the antenna supervisor configuration, the status of the antenna supervisor will be reported
in an NMEA ($GPTXT) or UBX (INF-NOTICE) message at start-up and on every change.
2.4.3 Power and short detection antenna supervisor
If a suitably dimensioned R_BIAS series resistor is placed in front of the V_ANT pin, a short circuit can
be detected in the antenna supply. The detection happens inside the u-blox M8 module, after which
the antenna supply voltage will be immediately shut down. Afterwards, periodic attempts to reestablish antenna power are made by default.
An internal switch (under control of the receiver) can turn off the supply to the external antenna
whenever it is not needed. This feature helps to reduce power consumption in power save mode.
☞ To configure the antenna supervisor, use the UBX-CFG-ANT message. For further information,
see the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification [3].
⚠ Short circuits on the antenna input without limitation (R_BIAS) of the current can result in
permanent damage to the receiver! Therefore, it is mandatory to implement an R_BIAS in all risk
applications, such as in situations where the antenna can be disconnected by the end-user or the
antenna cables are long.
☞ In case VCC_RF voltage does not match with the antenna supply voltage, use a filtered external
supply as shown in Figure 12.
Supply from VCC_RF
Figure 11 shows an active antenna supplied from the LEA-M8S / LEA-M8T module.
LEA-M8S module includes a built in antenna bias supply for nominal 3 V antennas enabled by linking
the filtered VCC_RF supply output pin to the V_ANT antenna supply input pin with a 10 Ohm resistor
in series. The module then controls the power supply to the antenna, applying power whenever the
receiver is active and removing power during power-save idle times and if a short-circuit is detected.
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Short-circuit is detected if the voltage at the antenna supply falls close to zero and is indicated as an
alarm in message MON-HW.
Figure 11: Module design with active antenna, internal supply from VCC_RF
External supply
Figure 12 shows an externally powered active antenna design.
Since the external bias voltage is fed into the most sensitive part of the receiver (the RF input), this
supply should be free of noise. Usually, low frequency analog noise is less critical than digital noise of
spurious frequencies with harmonics up to the GPS/QZSS band of 1.575 GHz, GLONASS band of
1.602 GHz and BeiDou band at 1.561 GHz. Therefore, it is not recommended to use digital supply nets
to feed the V_ANT pin.
Figure 12: Module design with active antenna, external supply
2.4.4 Power, short and open detection antenna supervisor
Optionally the ANT_DET_N pin may be reassigned to antenna supervision, allowing an external circuit
to indicate to the module that the antenna is open-circuit. This condition is reported by the module in
message MON-HW. Calculate the threshold current using Equation 1.
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RFVcc
Rbias
RR
R
I _
32
2
Figure 13: Schematic of open circuit detection
Equation 1: Calculation of threshold current for open circuit detection
☞ If the antenna supply voltage is not derived from VCC_RF, do not exceed the maximum voltage
rating of ANT_DET_N.
2.5 Layout design-in: Thermal management
During design-in do not place the module near sources of heating or cooling. The receiver oscillator is
sensitive to sudden changes in ambient temperature which can adversely impact satellite signal
tracking. Sources can include co-located power devices, cooling fans or thermal conduction via the
PCB. Take into account the following questions when designing in the module.
Is the receiver placed away from heat sources?
Is the receiver placed away from air-cooling sources?
Is the receiver shielded by a cover/case to prevent the effects of air currents and rapid
environmental temperature changes?
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Pin
LEA-6N
LEA-M8S
Remarks for migration
Pin name
Typical assignment
Pin name
Typical assignment
1
SDA
DDC data
SDA
DDC data
No difference
2
SCL
DDC clock
SCL
DDC clock
No difference
3
TxD
Serial port
TXD
Serial port
No difference
4
RxD
Serial port
RXD
Serial port
No difference
5
NC
Not connected
Reserved
Not connected
No difference
6
VCC
Supply voltage
VCC
Supply voltage
No difference
7
GND
Ground (digital)
GND
Ground (digital)
No difference
8
VCC_OUT
Output voltage
VCC_OUT
Output voltage
No difference
9
NC
Not connected
Reserved
Not connected
No difference
10
RESET_N
External reset
RESET_N
External reset
No difference
11
V_BCKP
Backup voltage supply
V_BCKP
Backup voltage supply
If this was connected to
GND on u-blox 6 module,
OK to do the same in M8.
12
Reserved
SAFEBOOT_N,
Do not drive low
SAFEBOOT_N
Do not drive low
No difference
13
GND
Ground
GND
Ground
No difference
14
GND
Ground
GND
Ground
No difference
15
GND
Ground
GND
Ground
No difference
16
RF_IN
GNSS signal input
RF_IN
GNSS signal input
No difference
17
GND
Ground
GND
Ground
No difference
18
VCC_RF
Output voltage RF section
VCC_RF
Output voltage RF section
No difference
19
V_ANT
Antenna bias voltage
V_ANT
Antenna bias voltage
No difference
20
AADET_N
Active antenna detect
EXTINT1
Active antenna detect
No difference
21
Reserved
Not connected
Reserved
Not connected
No difference
22
Reserved
Not connected
Reserved
Not connected
No difference
23
Reserved
Not connected
Reserved
Not connected
No difference
24
VDD_USB
USB supply
VDD_USB
USB supply
No difference
25
USB_DM
USB data
USB_DM
USB data
No difference
26
USB_DP
USB data
USB_DP
USB data
No difference
3 Migration to u-blox M8 modules
3.1 Migrating u-blox 6 designs to u-blox M8 module
u-blox is committed to ensuring that products in the same form factor are backwards compatible over
several technology generations. The utmost care has been taken to ensure there is no negative
impact on function or performance and to make u-blox M8 modules as fully compatible with previous
generation modules as possible. If using BeiDou, check the bandwidth of the external RF components
and the antenna. For information about power consumption, see the LEA-M8S Data sheet [1] and the
NEO / LEA-M8T Data sheet [2]. It is highly advisable that customers consider a design review with the
u-blox support team to ensure the compatibility of key functionalities.
☞ Selected pin names have been updated to agree with a common naming convention across u-blox
modules. The pins have not changed their operation and are the same physical hardware but with
updated names.
3.2 Hardware migration LEA-6N -> LEA-M8S
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27
EXTINT0
External interrupt pin
EXTINT0
External interrupt pin
No difference
28
TIMEPULSE
Timepulse (1PPS)
TIMEPULSE
Time pulse 1
No difference
Pin
LEA-6T
LEA-M8T
Remarks for migration
Pin name
Typical assignment
Pin name
Typical assignment
1
SDA
DDC data
SDA / SPI CS_N
DDC data
No difference
2
SCL
DDC clock
SCL / SPI CLK
DDC clock
No difference
3
TxD
Serial port
TXD / SPI MISO
Serial port
No difference
4
RxD
Serial port
RXD / SPI MOSI
Serial port
No difference
5
NC
Not connected
D_SEL
D_SEL =1 (or open)
Do not drive low
6
VCC
Supply voltage
VCC
Supply voltage
No difference
7
GND
Ground (digital)
GND
Ground (digital)
No difference
8
VCC_OUT
Output voltage
VCC_OUT
Output voltage
No difference
9
TIMEPULSE2
2nd Time pulse
Not Connected
Reserved
Time pulse 2 is now
available on pin 12
(TP2/SAFEBOOT_N)
10
RESET_N
External reset
RESET_N
External reset
No difference
11
V_BCKP
Backup voltage supply
V_BCKP
Backup voltage supply
If this was connected to
GND on u-blox 6 module,
OK to do the same in M8.
12
Reserved
Safeboot_N
TP2/SAFEBOOT
_N
Safeboot_N /Time pulse 2
Must not be held LO
during start-up.
13
GND
Ground
GND
Ground
No difference
14
GND
Ground
GND
Ground
No difference
15
GND
Ground
GND
Ground
No difference
16
RF_IN
GNSS signal input
RF_IN
GNSS signal input
No difference
17
GND
Ground
GND
Ground
No difference
18
VCC_RF
Output voltage RF section
VCC_RF
Output voltage RF section
No difference
19
V_ANT
Antenna bias voltage
V_ANT
Antenna bias voltage
No difference
20
AADET_N
Active antenna detect
EXTINT1
External interrupt pin/
Active antenna detect
21
Reserved
Not connected
Reserved
Not connected
No difference
22
Reserved
Not connected
Reserved
Not connected
No difference
23
Reserved
Not connected
Reserved
Not connected
No difference
24
VDD_USB
USB supply
VDD_USB
USB supply
No difference
25
USB_DM
USB data
USB_DM
USB data
No difference
26
USB_DP
USB data
USB_DP
USB data
No difference
27
EXTINT0
External interrupt pin
EXTINT0
External interrupt pin
No difference
28
TIMEPULSE1
Time pulse (1PPS)
TIMEPULSE1
Time pulse (1PPS)
No difference
Table 5: Pin-out comparison LEA-6N vs. LEA-M8S
3.3 Hardware migration LEA-6T -> LEA-M8T
Table 6: Pin-out comparison LEA-6T vs. LEA-M8T
3.4 Software migration
☞ For overall description of the module software operation, see the u-blox 8 / u-blox M8 Receiver
Description Including Protocol Specification [3]. For migration, see the u-blox M8 FW SPG3.01
Migration Guide [8].
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4 Product handling
4.1 Packaging, shipping, storage and moisture preconditioning
For information pertaining to reels and tapes, moisture sensitivity levels (MSL), shipment and storage
information, as well as drying for preconditioning see the LEA-M8S Data sheet [1] and NEO / LEAM8T Data sheet [2].
Population of modules
☞ When populating the modules, make sure that the pick and place machine is aligned to the copper
pins of the module and not on the module edge.
4.2 Soldering
Soldering paste
Use of “No Clean” soldering paste is strongly recommended, as it does not require cleaning after the
soldering process has taken place. The paste given in the example below meets these criteria.
Soldering paste: OM338 SAC405 / Nr.143714 (Cookson Electronics)
Alloy specification: Sn 95.5/ Ag 4/ Cu 0.5 (95.5% tin/ 4% silver/ 0.5% copper)
Melting temperature: 217 °C
Stencil thickness: See Figure 6.
The final choice of the soldering paste depends on the approved manufacturing procedures.
The paste-mask geometry for applying soldering paste must meet the recommendations.
☞ The quality of the solder joints on the connectors (’half vias’) must meet the appropriate IPC
specification.
Reflow soldering
A convection-type soldering oven is highly recommended over the infrared-type radiation oven.
Convection-heated ovens allow precise control of the temperature, and all parts will heat up evenly,
regardless of material properties, thickness of components and surface color.
As a reference, see the IPC-7530 Guidelines for temperature profiling for mass soldering (reflow and
wave) processes, published in 2001.
Preheat phase
During the initial heating of component leads and balls, residual humidity will be dried out. Note that
this preheat phase will not replace prior baking procedures.
Temperature rise rate: max 3 °C/s. If the temperature rise is too rapid in the preheat phase it may
cause excessive slumping.
Time: 60 – 120 s. If the preheat is insufficient, rather large solder balls tend to generate.
Conversely, if performed excessively, fine balls and large balls will generate in clusters.
End temperature: 150 – 200 °C. If the temperature is too low, non-melting tends to be caused in
areas containing large heat capacity.
Heating/ Reflow phase
The temperature rises above the liquidus temperature of 217 °C. Avoid a sudden rise in temperature
as the slump of the paste could become worse.
Limit time above 217 °C liquidus temperature: 40 – 60 s
Peak reflow temperature: 245 °C
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Cooling phase
A controlled cooling avoids negative metallurgical effects of the solder (the solder becomes more
brittle) and possible mechanical tensions in the products. Controlled cooling helps to achieve bright
solder fillets with good shape and low contact angle.
Temperature fall rate: max 4 °C/s
☞ To avoid falling off, place the u-blox M8 GNSS module on the topside of the motherboard during
soldering.
The final soldering temperature chosen at the factory depends on additional external factors such as
choice of soldering paste, size, thickness and properties of the baseboard. Exceeding the maximum
soldering temperature in the recommended soldering profile may permanently damage the module.
Figure 14: Recommended soldering profile
☞ u-blox M8 modules must not be soldered with a damp heat process.
Optical inspection
After soldering the u-blox M8 module, consider an optical inspection step to check whether:
The module is properly aligned and centered over the pads.
All pads are properly soldered.
No excess solder has created contacts to neighboring pads, or possibly to pad stacks and vias
nearby.
Cleaning
In general, cleaning the populated modules is strongly discouraged. Residues underneath the
modules cannot be easily removed with a washing process.
Cleaning with water will lead to capillary effects where water is absorbed into the gap between the
baseboard and the module. The combination of residues of soldering flux and encapsulated water
leads to short circuits or resistor-like interconnections between neighboring pads.
Cleaning with alcohol or other organic solvents can result in soldering flux residues flooding into
the two housings, areas that are not accessible for post-wash inspections. The solvent will also
damage the sticker and the ink-jet printed text.
Ultrasonic cleaning will permanently damage the module, in particular the quartz oscillators.
The best approach is to use a “no clean” soldering paste and eliminate the cleaning step after the
soldering.
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Repeated reflow soldering
Only single reflow soldering processes are recommended for boards populated with u-blox M8
modules. To avoid upside down orientation during the second reflow cycle, the M8 modules should not
be submitted to two reflow cycles on a board populated with components on both sides. In such a
case, the module should always be placed on that side of the board which is submitted into the last
reflow cycle. This is because of the risk of the module falling off due to the significantly higher weight
in relation to other components.
You can consider two reflow cycles by excluding the above described upside down scenario and taking
into account the rework conditions described in section 4.
☞ Repeated reflow soldering processes and soldering the module upside down are not
recommended.
Wave soldering
Baseboards with combined through-hole technology (THT) components and surface-mount
technology (SMT) devices require wave soldering to solder the THT components. Only a single wave
soldering process is encouraged for boards populated with u-blox M8 modules.
Hand soldering
Hand soldering is allowed. Use a soldering iron temperature-setting equivalent to 350 °C. Place the
module precisely on the pads. Start with a cross-diagonal fixture soldering (for example, pins 1 and
15), and continue from left to right.
Rework
The u-blox M8 module can be unsoldered from the baseboard using a hot air gun. When using a hot
air gun for unsoldering the module, a maximum of one reflow cycle is allowed. Using a hot air gun is
not recommended because it is an uncontrolled process and might damage the module.
⚠ Attention: use of a hot air gun can lead to overheating and severely damage the module. Always
avoid overheating the module.
After the module is removed, clean the pads before placing and hand soldering a new module.
⚠ Never attempt a rework on the module itself, for example, by replacing individual components.
Such actions immediately terminate the warranty.
In addition to the two reflow cycles, manual rework on particular pins by using a soldering iron is
allowed. Manual rework steps on the module can be done several times.
Conformal coating
Certain applications employ a conformal coating of the PCB using HumiSeal® or other related coating
products. These materials affect the HF properties of the GNSS module and it is important to prevent
them from flowing into the module. The RF shields do not provide 100% protection for the module
from coating liquids with low viscosity; therefore, take care when applying the coating.
☞ Conformal coating of the module will void the warranty.
Casting
If casting is required, use viscose or another type of silicon pottant. The OEM is strongly advised to
qualify such processes in combination with the u-blox M8 module before implementing it in the
production.
☞ Casting will void the warranty.
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Grounding metal covers
Attempts to improve grounding by soldering ground cables, wick or other forms of metal strips
directly onto the EMI covers is done at the customer’s own risk. The numerous ground pins should be
sufficient to provide optimum immunity to interferences and noise.
☞ u-blox offers no warranty against damages to the u-blox M8 module caused by soldering metal
cables or any other forms of metal strips directly onto the EMI covers.
Use of ultrasonic processes
Some components on the u-blox M8 module are sensitive to ultrasonic waves. Use of any ultrasonic
processes (cleaning, welding, and so on) may cause damage to the GNSS receiver.
☞ u-blox offers no warranty against damages to the u-blox M8 module caused by any ultrasonic
processes.
4.3 EOS/ESD/EMI precautions
When integrating GNSS positioning modules into wireless systems, consider the electromagnetic
and voltage susceptibility issues carefully. Wireless systems include components that can produce
electrical overstress (EOS) and electro-magnetic interference (EMI). CMOS devices are more sensitive
to such influences because their failure mechanism is defined by the applied voltage, whereas bipolar
semiconductors are more susceptible to thermal overstress. The following design guidelines help you
in designing robust yet cost effective solutions.
⚠ To avoid overstress damage during production or in the field, it is essential to observe strict
EOS/ESD/EMI handling and protection measures.
⚠ To prevent overstress damage at the RF_IN of your receiver, never exceed the maximum input
power (see the LEA-M8S Data sheet [1] and the NEO-M8T / LEA-M8T Data sheet [2]).
Electrostatic discharge (ESD)
Electrostatic discharge (ESD) is the sudden and momentary electric current that flows
between two objects at different electrical potentials caused by direct contact or
induced by an electrostatic field. The term is usually used in the electronics and other
industries to describe momentary unwanted currents that may cause damage to
electronic equipment.
ESD handling precautions
ESD prevention is based on establishing an electrostatic protective area (EPA). The EPA can be a
small working station or a large manufacturing area. The main principle of the EPA is that there are
no highly charging materials near ESD-sensitive electronics, all conductive materials and workers are
grounded, and charge build-up on ESD-sensitive electronics is prevented. International standards are
used to define typical EPA and can be obtained for example from International Electrotechnical
Commission (IEC) or American National Standards Institute (ANSI).
GNSS positioning modules are sensitive to ESD and require special precautions when handling.
Particular care must be exercised when handling patch antennas, due to the risk of electrostatic
charges. In addition to standard ESD safety practices, take the following measures into account
whenever handling the receiver.
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Unless there is a galvanic coupling between the local GND
(the work table) and the PCB GND, the first point of contact
when handling the PCB must always be between the local
GND and PCB GND.
Before mounting an antenna patch, connect ground of the
device.
When handling the RF pin, do not come into contact with
any charged capacitors and be careful when contacting
materials that can develop charges (such as patch antenna
~10 pF, coax cable ~50 – 80 pF/m, soldering iron).
To prevent electrostatic discharge through the RF input, do
not touch any exposed antenna area. If there is any risk that
such exposed antenna area is touched in a non-ESD
protected work area, implement proper ESD protection
measures in the design.
When soldering RF connectors and patch antennas to the
receiver’s RF pin, make sure to use an ESD-safe soldering
iron (tip).
Small passive antennas (<2 dBic and
performance critical)
Passive antennas (>2 dBic or
performance sufficient)
Active antennas
A
RF
_IN
GNSS
Receiver
LNA
B
L
RF
_IN
GNSS
Receiver
C
D
RF
_IN
GNSS
Receiver
LNA with appropriate ESD rating
⚠ Failure to observe these precautions can result in severe damage to the GNSS module!
ESD protection measures
⚠ GNSS positioning modules are sensitive to electrostatic discharge (ESD). Special precautions are
required when handling.
☞ For more robust designs, employ additional ESD protection measures. Using an LNA with the
appropriate ESD rating can provide enhanced GNSS performance with passive antennas and
increases ESD protection.
Most defects caused by ESD can be prevented by following strict ESD protection rules for production
and handling. When implementing passive antenna patches or external antenna connection points,
additional ESD measures can also avoid failures in the field as shown in Figure 15.
Figure 15: ESD precautions
☞ Protection measure A is preferred because it offers the best GNSS performance and the best level
of ESD protection.
Electrical overstress (EOS)
Electrical overstress (EOS) usually describes situations where the maximum input power exceeds the
maximum specified ratings. EOS failure can happen if RF emitters are close to a GNSS receiver or its
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Small passive antennas (<2 dBic
and performance critical)
Passive antennas (>2 dBic or
performance sufficient)
Active antennas (without internal filter which
needs the module antenna supervisor circuits)
D
RF
_IN
GNSS
Receiver
LNA
GPS
Bandpass
Filtler
E
RF
_IN
GNSS
Receiver
L
GPS
Bandpass
Filtler
F
LNA with appropriate ESD rating
and maximum input power
GNSS band pass Filter: SAW or
ceramic with low insertion loss
and appropriate ESD rating
antenna. EOS causes damage to the chip structures. If the RF_IN is damaged by EOS, it is hard to
determine whether the chip structures have been damaged by ESD or EOS.
EOS protection measures
☞ For designs with GNSS positioning modules and wireless (for example, GSM/GPRS) transceivers
in close proximity, ensure sufficient isolation between the wireless and GNSS antennas. If wireless
power output causes the specified maximum power input at the GNSS RF_IN to exceed, employ
EOS protection measures to prevent overstress damage.
For robustness, EOS protection measures as shown in Figure 16 are recommended for designs
combining wireless communication transceivers (for example, GSM, GPRS) and GNSS in the same
design or in close proximity.
Figure 16: EOS and ESD precautions
Electromagnetic interference (EMI)
Electromagnetic interference (EMI) is the addition or coupling of energy causing a spontaneous reset
of the GNSS receiver or resulting in unstable performance. In addition to EMI degradation due to selfjamming (see section 1.5), any electronic device near the GNSS receiver can emit noise that can lead
to EMI disturbances or damage.
The following elements are critical regarding EMI:
Unshielded connectors (for example, pin rows)
Weakly shielded lines on PCB (for example, on the top or the bottom layer and especially at the
border of a PCB)
Weak GND concept (for example, small and/or long ground line connections)
EMI protection measures are recommended when RF-emitting devices are near the GNSS receiver.
To minimize the effect of EMI, a robust grounding concept is essential. To achieve electromagnetic
robustness, follow the standard EMI suppression techniques:
http://www.murata.com/products/emc/knowhow/index.html
http://www.murata.com/products/emc/knowhow/pdf/4to5e.pdf
Improved EMI protection can be achieved by inserting a resistor or, better yet, a ferrite bead or an
inductor (see Table 8: Recommended parts
) into any unshielded PCB lines connected to the GNSS receiver. Place the resistor as close to the
GNSS receiver pin as possible.
Alternatively, feed-through capacitors with good GND connection can be used to protect, for example,
the VCC supply pin against EMI. A selection of feed-through capacitors is listed in Table 8.
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1525 1550 1625
GPS input filter
characteristics
1575 1600
0
-110
Jammin
g signal
1525 1550 1625
Frequency [MHz]
Power [dBm]
GPS input filter
characteristics
1575 1600
0
Jamming
signal
GPS
signals
GPS Carrier
1575.4 MHz
Intended use
☞ To mitigate any performance degradation of a radio equipment under EMC disturbance, system
integration shall adopt appropriate EMC design practice and shall not contain cables over three
meters on signal and supply ports.
4.4 Applications with cellular modules
GSM terminals transmit power levels up to 2 W (+33 dBm) peak, 3G and LTE up to 250 mW
continuous. Consult the LEA-M8S Data sheet [1] and the NEO-M8T / LEA-M8T Data sheet [2] for the
absolute maximum power input at the GNSS receiver.
☞ See GPS Implementation and Aiding Features in u-blox Wireless Modules [7].
Isolation between GNSS and GSM antenna
In a handheld-type design, an isolation of approximately 20 dB can be reached with careful placement
of the antennas. If such isolation cannot be achieved, for example, in the case of an integrated cellular
/GNSS antenna, an additional input filter is needed on the GNSS side to block the high energy emitted
by the GSM transmitter. Examples of these kinds of filters are SAW Filters from Epcos (B9444 or
B7839) or Murata.
Increasing interference immunity
Interference signals come from in-band and out-band frequency sources.
In-band interference
With in-band interference, the signal frequency is very close to the GNSS constellation frequency
used, for example, GPS frequency of 1575 MHz (see Figure 17). Such interference signals are typically
caused by harmonics from displays, micro-controller, bus systems, and so on.
Figure 17: In-band interference signals
Figure 18: In-band interference sources
Measures against in-band interference include:
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Maintaining a good grounding concept in the design
Shielding
Layout optimization
Filtering
Placement of the GNSS antenna
Adding a CDMA, GSM, WCDMA band pass filter before handset antenna
Out-band interference
Out-band interference is caused by signal frequencies that are different from the GNSS carrier (see
Figure 19). The main sources are wireless communication systems such as cellular, CDMA, WCDMA,
Wi-Fi, BT, and so on.
Figure 19: Out-band interference signals
Measures against out-band interference include maintaining a good grounding concept in the design
and adding a SAW or band pass ceramic filter (as recommend in section 4) into the antenna input line
to the GNSS receiver (see Figure 20).
Figure 20: Measures against in-band interference
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Abbreviation
Definition
ANSI
American National Standards Institute
BeiDou
Chinese navigation satellite system
CDMA
Code Division Multiple Access
EMC
Electromagnetic compatibility
EMI
Electromagnetic interference
EOS
Electrical Overstress
EPA
Electrostatic Protective Area
ESD
Electrostatic discharge
Galileo
European navigation system
GLONASS
Russian satellite system
GND
Ground
GNSS
Global Navigation Satellite System
GPS
Global Positioning System
GSM
Global System for Mobile Communications
IEC
International Electrotechnical Commission
PCB
Printed circuit board
QZSS
Quasi-Zenith Satellite System
Manufacturer
Part ID
Remarks
Parameters to consider
Diode ON
Semiconductor
ESD9R3.3ST5G
Standoff voltage>3.3 V
Low capacitance < 0.5 pF
ESD9L3.3ST5G
Standoff voltage>3.3 V
Standoff voltage > Voltage for active
antenna
ESD9L5.0ST5G
Standoff voltage>5 V
Low inductance
SAW
TDK/ EPCOS
B8401: B39162-B8401P810
GPS+GLONASS
High attenuation
TDK/ EPCOS
B3913: B39162B3913U410
GPS+GLONASS+BeiDou
For automotive applications
TDK/ EPCOS
B4310: B39162B4310P810
GPS+GLONASS
Compliant to the AEC-Q200 standard
ReyConns
NDF9169
GPS+ BeiDou
Low insertion loss, only for mobile
applications
Murata
SAFFB1G56KB0F0A
GPS+GLONASS+BeiDou
Low insertion loss, only for mobile
applications
Murata
SAFEA1G58KB0F00
GPS+GLONASS
Low insertion loss, only for mobile
applications
Murata
SAFEA1G58KA0F00
GPS+GLONASS
High attenuation, only for mobile
applications
Murata
SAFFB1G58KA0F0A
GPS+GLONASS
High attenuation, only for mobile
applications
Murata
SAFFB1G58KB0F0A
GPS+GLONASS
Low insertion loss, only for mobile
applications
Appendix
A Glossary
Table 7: Explanation of the abbreviations and terms used
B Recommended parts
Recommended parts are selected on data sheet basis only. Other components may also be used.
UBX-15030060 - R06 Appendix Page 30 of 33
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Manufacturer
Part ID
Remarks
Parameters to consider
TAI-SAW
TA1573A
GPS+GLONASS
Low insertion loss
TAI-SAW
TA1343A
GPS+GLONASS+BeiDou
Low insertion loss
TAI-SAW
TA0638A
GPS+GLONASS+BeiDou
Low insertion loss
LNA
JRC
NJG1143UA2
LNA
Low noise figure, up to 15 dBm RF input
power
Inductor
Murata
LQG15H series, e.g.
LQG15HS47NJ02
LQG15HN27NJ02
L, 47 nH down to 27 nH
Impedance at freq. GNSS > 500
Murata
LQW15A series, e.g.
LQW15AN47NJ80
LQW15AN75NJ80
L, 47 nH up to 75 nH
Johansson
Technology
L-07W series e.g. 39 nH L07W39NJV4T
or any other inductance
compatible with the
above Murata inductors
Capacitor
Murata
GRM1555C1E470JZ01
C
DC-block
, 47 pF
DC-block
Murata
X7R 10N 10% 16 V
C
Bias
, 10 nF
Bias-T
Ferrite
bead
Murata
BLM15HD102SN1
FB
High IZI at fGSM
Feedthrough
capacitor
for signal
Murata
NFL18SP157X1A3
Monolithic type
For data signals, 34 pF load capacitance
NFA18SL307V1A45
Array type
For data signals, 4 circuits in 1 package
Feedthrough
capacitor
Murata
NFM18PC ….
NFM21P….
0603 2A
0805 4A
Rs < 0.5
Resistor
10 10%, min 0.250 W
R
bias
560 5%
R2
100 k 5%
R3, R4
Manufacturer
Order no.
Comments
Hirschmann (www.hirschmann-car.com)
GLONASS 9 M
GPS+GLONASS active
Taoglas (www.taoglas.com )
AA.160.301111
36 x 36 x 4 mm, 3-5V 30 mA active
Taoglas (www.taoglas.com )
AA.161.301111
36 x 36 x 3 mm, 1.8 to 5.5 V / 10 mA at 3 V active
INPAQ (http://www.inpaq.com.tw/)
B3G02G-S3-01-A
2.7 to 3.9 V / 10 mA active
Amotech (www.amotech.co.kr)
B35-3556920-2J2
35 x 35 x 3 mm GPS+GLONASS passive
Amotech (www.amotech.co.kr)
A25-4102920-2J3
25 x 25 x 4 mm GPS+GLONASS passive
Amotech (www.amotech.co.kr)
A18-4135920-AMT04
18 x 18 x 4 mm GPS+GLONASS passive
Amotech (www.amotech.co.kr)
Amotech AGA363913S0-A1
GPS+GLONASS+ BeiDou active
INPAQ (http://www.inpaq.com.tw/)
ACM4-5036-A1-CC-S
5.2 x 3.7 x 0.7 mm GPS+GLONASS passive
Additional antenna Manufacturer: Allis Communications, 2J, Tallysman Wireless
Table 8: Recommended parts
Recommended antennas
Table 9: Recommend antennas
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Revision
Date
Name
Comments
R01
12-Feb-2016
jfur
Objective Specification
R02
15-June-2016
jfur
Advance Information, Pin name updated
R03
08-Aug-2016
jfur
Production Information
R04
26-Sep-2017
msul
Added information on RED DoC in European Union regulatory compliance
(page 2), added Intended use statement in section 4.3 Electromagnetic
interference (EMI), updated legal statement in cover page and added
Documentation feedback e-mail address in contacts page.
R05
25-Feb-2019
rmak
Added information on EXTINT0 pin usage as a generic PIO13 in Section 1.5.2
and in Table 2. Updated Table 8.
R06
05-May-2020
mala, dama
Added section Layout design-in: Thermal management in Chapter 2.
Updated document information section for LEA-M8T-1-00 product.
Related documents
[1] LEA-M8S (FW3) Data sheet, doc. no. UBX-16010205
[2] NEO / LEA-M8T (FW3) Data sheet, doc. no. UBX-15025193
[3] u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification (Public version), doc.
no. UBX-13003221
[4] GPS Antenna application note, doc. no. GPS-X-08014
[5] GPS Compendium, doc. no. GPS-X-02007
[6] I2C-bus specification, Rev. 6 - 4 April 2014,
http://www.nxp.com/documents/user_manual/UM10204.pdf
[7] GPS Implementation and Aiding Features in u-blox Wireless Modules, doc. no. GSM.G1-CS-
09007
[8] u-blox M8 FW SPG3.01 migration guide, doc. no. UBX-15028330
☞ For regular updates to u-blox documentation and to receive product change notifications, register
on our homepage (www.u-blox.com).
Revision history
UBX-15030060 - R06 Related documents Page 32 of 33
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