u-blox NEO-M8U, NEO-M8U-04B-00, NEO-M8L Hardware Integration Manual

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NEO-M8U

u-blox M8 Untethered Dead Reckoning module including 3D inertial sensors

Hardware Integration Manual

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Abstract

This document describes the features and specifications of NEO-M8U, a high-

performance

untethered dead reckoning module with 3D sensors. The module includes the u-

blox M8 concurrent

GNSS engine with reception of GPS, GLONASS, BeiDou, Galileo and QZSS signals.

www.u-blox.com

UBX-15016700 - R07

NEO-M8U - Hardware Integration Manual

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Document Information

Title NEO-M8U

Subtitle u-blox M8 Untethered Dead Reckoning module including 3D inertial sensors

Document type Hardware Integration Manual

Document number UBX-15016700

Revision and date R07 18-Apr-2019

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.

European Union regulatory compliance

NEO-M8U compile with all relevant requirements for RED 2014/53/EU. The NEO-M8U

Declaration of

Conformity (DoC) is available at www.u-blox.com within Support > Product resources > Conformity Declaration.

This document applies to the following products:

Product name Type number ROM/FLASH version PCN reference

NEO-M8U NEO-M8U-04B-00 FLASH FW 3.01 UDR 1.21 N/A

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.

-blox AG.

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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 ............................................................................................................. 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 .......................................................................................................................................................... 7

1.4.5 TX Ready signal ................................................................................................................................... 8

1.5 I/O pins ........................................................................................................................................................... 8

1.5.1 Electromagnetic interference on I/O lines ..................................................................................... 8

2 Design ..................................................................................................................................................... 10

2.1 Pin description ........................................................................................................................................... 10

2.1.1 Pin name changes............................................................................................................................. 11

2.2 Minimal design........................................................................................................................................... 11

2.3 Layout: Footprint and paste mask ........................................................................................................ 11

2.4 Antenna ....................................................................................................................................................... 12

2.4.1 Antenna design with passive antenna ......................................................................................... 12

2.4.2 Active antenna design ..................................................................................................................... 13

3 Untethered Dead Reckoning ........................................................................................................... 15

3.1 Implementation ......................................................................................................................................... 15

3.2 Installation .................................................................................................................................................. 15

3.3 Initialization and Calibration ................................................................................................................... 15

4 Migration from NEO-M8L to NEO-M8U ...................................................................................... 16

4.1 Hardware migration NEO-M8L to NEO-M8U ...................................................................................... 16

5 Product handling ................................................................................................................................. 17

5.1 Packaging, shipping, storage and moisture preconditioning .......................................................... 17

5.2 Soldering ..................................................................................................................................................... 17

5.3 EOS/ESD/EMI precautions ...................................................................................................................... 20

5.4 Applications with cellular modules ........................................................................................................ 23

Appendix ....................................................................................................................................................... 25

A Glossary ................................................................................................................................................. 25

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Related documents ................................................................................................................................... 27

Revision history .......................................................................................................................................... 27

Contact .......................................................................................................................................................... 28

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1 Hardware description

1.1 Overview

The NEO-M8U is an Untethered Dead Reckoning module bringing the benefits of dead reckoning to a wider range of road-vehicle applications by eliminating the need for a speed or wheel-tick connection to the vehicle. The module uses built-in gyroscope and accelerometer sensors and features the high performance u-blox M8 concurrent positioning engine. Available in the NEO industry standard leadless chip carrier (LCC) package, it is easy to integrate and combines exceptional positioning performance with highly flexible power, design, and connectivity options. SMT pads allow fully automated assembly with standard pick & place and reflow-soldering equipment for cost-efficient, high-volume production enabling short time-to-market.

☞ For more about product features see the

NEO-M8U Data Sheet

[1].

☞ To determine which u-blox product best meets your needs, see the product selector tables on the

u-blox website www.u-blox.com.

1.2 Configuration

The configuration settings can be modified using UBX protocol configuration messages (see

u-blox 8

/ u-blox M8 Receiver Description Including Protocol Specification

[2]). The modified settings remain effective until power-down or reset. If these settings have been stored in BBR (Battery Backed RAM), then the modified configuration will be retained, as long as there is no backup battery supply interrupt.

For NEO-M8U modules, the configuration can be saved permanently in SQI flash.

1.3 Connecting power

The NEO-M8U positioning module has 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. For this reason, it is important that the supply circuitry be able to support the peak power for a short time (see the

NEO-M8U Data Sheet

[1] for specification).

☞ When switching from backup mode to normal operation or at start-up, the NEO-M8U module must

charge the internal capacitors in the core domain. In certain situations, this can result in a significant current draw. 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, as with hot starts, warm starts, AssistNow Autonomous and AssistNow Offline. If no backup battery is connected, the module performs a cold start at power up.

☞ A backup supply voltage should be provided to the NEO-M8U to enable navigation by Dead

Reckoning before the first GNSS fix.

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☞ 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.

☞ If no backup supply voltage is available, connect the V_BCKP pin to VCC.

☞ As long as power is supplied to the NEO-M8U module through the VCC pin, 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

NEO-M8U Data Sheet

[1])

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

The VCC_RF pin can supply an active antenna or external LNA. For more information, see section 0

1.4 Interfaces

1.4.1 UART

NEO-M8U 3D dead reckoning module includes a Universal Asynchronous Receiver Transmitter (UART) serial interface RXD/TXD supporting configurable baud rates. The baud rates supported are specified in the

NEO-M8U Data Sheet

[1].

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. These drivers are available at our website at www.u-blox.com

USB external components

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.

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In USB self-powered mode, 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 would still receive 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, i.e. VBUS is not supplied.

☞ USB bus-powered mode is not supported.

Module

VDD_USB

LDO

VDD_USB

USB_DP

USB_DM

C24 C23

VBUS

GND

USB Device Connector

EN R11

Figure 2: USB Interface

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) if the GNSS receiver is operated as a USB self-powered device.

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 Ω

A value of 27 Ω is recommended.

R11 Resistor

100 kΩ is recommended for USB self-powered setup.

Table 1: Summary of USB external components

1.4.3 Display Data Channel (DDC)

An I2C compatible Display Data Channel (DDC) interface is available with a NEO-M8U module 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 I

C 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

[2]. For bandwidth information, see the

NEO-M8U Data

Sheet

[1]. For timing, parameters consult the

I2C-bus specification

[5].

☞ The NEO-M8U DDCy intyerface supports serial communication with u-blox cellular modules. See

the specification of the applicable cellular module to confirm compatibility.

1.4.4 SPI

An SPI interface is available for communication to a host CPU.

☞ SPI is not available in the deyfault 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-M8U Data Sheet

[1].

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1.4.5 TX Ready signal

The TX Ready signal indicates that 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 signal can be mapped to UART 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

[6].

1.5 I/O pins

RESET_N: Reset input

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, or as a POR. With the NEO-M8U module the RESET_N pin is an input only.

D_SEL: Interface select

The D_SEL pin selects the available interfaces. SPI cannot be used simultaneously with the UART/DDC. If open, UART and DDC are available. If pulled low, the SPI interface is available. More information see the

NEO-M8U Data Sheet

[1].

LNA_EN: LNA enable

In Power Save Mode, the system can turn on/off an optional external LNA using the LNA_EN signal in order to optimize power consumption.

TIMEPULSE

A configurable time pulse signal is available with the NEO-M8U module. It generates pulse trains synchronized with GPS or UTC time grid with intervals configurable over a wide frequency range. The time pulse signal is disabled by default. For more information, see the

u-blox 8 / u-blox M8 Receiver

Description Including Protocol Specification

[2].

☞ The NEO-M8U time-pulse output is configured using messages for “TIMEPULSE2”.

☞ The time-pulse output must not be held LOW during start-up.

1.5.1 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 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 when this noise is coupled into the GNSS antenna (see Figure 15).

To avoid interference by improperly shielded lines, it is recommended to use resistors (e.g. R>20 Ω), ferrite beads (e.g. BLM15HD102SN1) or inductors (e.g. LQG15HS47NJ02) on the I/O lines in series. These components should be chosen with care because they will affect also the signal rise times.

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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 5.3.

Figure 3: EMI Precautions Design

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2 Design

2.1 Pin description

No Name I/O Description

1 SAFEBOOT_N I SAFEBOOT_N, Test-point for service use (Leave OPEN)

2 D_SEL I Interface select

3 TIMEPULSE I/O Time pulse (disabled by default). Do not pull low during reset.

Note: configured using TIMEPULSE2 messages (see

u-blox 8 / u-blox M8

Receiver Description Including Protocol Specification

[2])

4 EXTINT I External Interrupt Pin (disabled by default).

5 USB_DM I/O USB Data

6 USB_DP I/O USB Data

7 VDD_USB I USB Supply

8 RESET_N I RESET_N

9 VCC_RF O Output Voltage RF section

10 GND I Ground

11 RF_IN I GNSS signal input

12 GND I Ground

13 GND I Ground

14 LNA_EN O Antenna / External LNA control

15 Reserved - Reserved

16 Reserved - Reserved

17 Reserved - Reserved

18 SDA /

SPI CS_N

I/O DDC Data if D_SEL =1 (or open)

SPI Chip Select if D_SEL = 0

19 SCL /

SPI CLK

I/O DDC Clock if D_SEL =1(or open)

SPI Clock if D_SEL = 0

20 TXD /

SPI MISO

O Serial Port if D_SEL =1(or open)

SPI MISO if D_SEL = 0

21 RXD /

SPI MOSI

I Serial Port if D_SEL =1(or open)

SPI MOSI if D_SEL = 0

22 V_BCKP I Backup voltage supply

23 VCC I Supply voltage

24 GND I Ground

Table 2: Pinout of NEO-M8U

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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 name along with their old and new names.

No Previous Name New name

14 ANT_ON LNA_EN

18 SDA

SPI CS_N

SDA / SPI CS_N

19 SCL

SPI CLK

SCL / SPI CLK

20 TxD

SPI MISO

TXD / SPI MISO

21 RxD

SPI MOSI

RXD / SPI MOSI

Table 3: Pin name changes in NEO-M8U

2.2 Minimal design

This is a minimal design for a NEO-M8U GNSS receiver.

Figure 4: NEO-M8U passive antenna design

☞ Use series resistors in the UART lines to avoid electromagnetic interference as mentioned in

section

1.5.1.

2.3 Layout: Footprint and paste mask

Figure 5 describes the footprint and provides recommendations for the paste mask for NEO-M8U 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 section 5.2.

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☞ Consider the paste mask outline when defining the minimal distance to the next component. The

exact geometry, distances, stencil thicknesses and solder paste volumes must be adapted to the specific production processes (e.g. soldering) of the customer.

2.4 Antenna

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, care should be taken 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 Ω.

Figure 6 shows a minimal setup for a design with a good GNSS patch antenna. For exact pin orientation, see the

NEO-M8U Data Sheet

[1].

Figure 6: Module design with passive antenna

☞ Use an antenna that has sufficient bandwidth to receive all GNSS constellations. For more

information see the appendix and the

GPS Antenna Application Note

[3].

Stencil: 170

10.4 mm [409.5 mil]

14.6 mm [575 mil]

12.2 mm [480 mil]

0.8 mm [31.5

mil

]

0.6 mm [23.5

mil

]

12.2 mm [480.3 mil]

16.0 mm [630

mil

]

1.0 mm

[39.3

mil]

0.8 mm [31.5

mil

]

0.8 mm

[31.5

mil

]

3.0 mm [118.1

mil

]

1.0 mm [39.3

mil

]

1.1 mm [43.3

mil

]

Figure

5: NEO-M8U footprint / NEO-M8U paste mask

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Figure 7 shows a design using an external LNA and SAW to increase the sensitivity for best performance with passive antenna. For exact pin orientation, see the

NEO-M8U Data Sheet

[1].

Figure 7: Module design with passive antenna and an external LNA and SAW

The LNA_EN pin (LNA enable) can be used to turn on and off an optional 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/GLONASS/BeiDou signals.

2.4.2 Active antenna design

An active antenna makes use of an integrated low-noise amplifier, which requires a power supply that will contribute to the total GNSS system power consumption budget with additional 5 to 20 mA typically.

If the supply voltage of the NEO-M8U module matches the supply voltage of the active antenna (e.g.

3.0 V), use the filtered supply voltage available at pin VCC_RF as shown in Figure 8. For exact pin orientation, see the

NEO-M8U Data Sheet

[1].

Active antenna design using VCC_RF pin to supply the active antenna

Figure 8: Active antenna design, external supply from VCC_RF

If the VCC_RF voltage does not match with the supply voltage of the active antenna, use a filtered external supply as shown in Figure 9. For exact pin orientation, see the

NEO-M8U Data Sheet

[1].

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Active antenna design powered from an external supply

Figure 9: Active antenna design, direct external supply

☞ The circuit shown in Figure 9 works with all u-blox M8 modules, including modules without VCC_RF

output.

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3 Untethered Dead Reckoning

3.1 Implementation

The NEO-M8U 3D Untethered Dead Reckoning module makes use of GNSS and internal gyroscope and accelerometer sensors only with no need or provision for speed pulse or forward/reverse information.

3.2 Installation

In order to achieve good performance, the NEO-M8U hardware needs to be mounted in the vehicle in such a way that its alignment is stable to within 2°. It is important that the mounting design minimizes vibration and mechanical resonance.

Figure 10: NEO-M8U with IMU sensor frame

3.3 Initialization and Calibration

The benefits of dead reckoning are available once the receiver has completed its initialization phase following installation. Initialization parameter values are subsequently stored in the battery-backed RAM (BBR) for immediate use, and may also be saved in Flash memory. The duration of the initialization depends on the quality of the GNSS signals as well as the dynamics encountered by the vehicle.

For details on Initialization and calibration, see the

u-blox 8 / u-blox M8 Receiver Description Including

Protocol Specification

[2].

☞ Note that the performance of the UDR solution relies on a stable sensor location and orientation

with respect to the vehicle frame. The module must be mounted securely within the vehicle.

☞ To read more about mandatory and optional configuration parameters, see the UDR configuration

section of

u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification

[2].

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4 Migration from NEO-M8L to NEO-M8U

4.1 Hardware migration NEO-M8L to NEO-M8U

u-blox is committed to ensuring that NEO-M8U are backwards compatible to NEO-M8L. It is highly advisable that customers consider a design review with the u-blox support team to ensure the compatibility of key functionalities.

NEO-M8L NEO-M8U Remarks for Migration

Pin Name Typical Assignment Pin Name Typical Assignment

1 SAFEBOOT_N Leave open. SAFEBOOT_N Leave open. No difference

2 D_SEL selects the interface D_SEL selects the interface No difference

3 TIMEPULSE Timepulse (1PPS) TIMEPULSE Timepulse (1PPS) No difference

4 WHEELTICK Wheel-tick input EXTINT External Interrupt Pin

(disabled by default).

No problem, disabled by default.

5 USB_DM USB Data USB_DM USB Data No difference

6 USB_DP USB Data USB_DP USB Data No difference

7 VDD_USB USB Supply VDD_USB USB Supply No difference

8 RESET_N Reset input RESET_N Reset input No difference

9 VCC_RF Can be used for active

antenna or external LNA supply

VCC_RF Can be used for active

antenna or external LNA supply

No difference

10 GND GND GND GND No difference

11 RF_IN GNSS signal input RF_IN GNSS signal input No difference

12 GND GND GND GND No difference

13 GND GND GND GND No difference

14 LNA_EN1

Used to turn on and off

an optional external LNA

LNA_EN Used to turn on and off an

optional external LNA

No difference

15 FWD Forward/reverse input

for speed pulse

RESERVED Leave open. If it was connected on NEO-M8L,

OK to do the same on NEO-M8U.

16 RESERVED2 Leave open. RESERVED Leave open. If it was connected on NEO-M8L,

OK to do the same on NEO-M8U.

17 RESERVED2 Leave open. RESERVED Leave open. If it was connected on NEO-M8L,

OK to do the same on NEO-M8U.

18 SDA DDC Data / SPI CS_N SDA DDC Data / SPI CS_N No difference

19 SCL DDC Clock / SPI SCK SCL DDC Clock / SPI SCK No difference

20 TXD Serial Port / SPI MISO TXD Serial Port / SPI MISO No difference

21 RXD Serial Port / SPI MOSI RXD Serial Port / SPI MOSI No difference

22 V_BCKP Backup Supply Voltage V_BCKP Backup Supply Voltage No difference

23 VCC Supply voltage VCC Supply voltage No difference

24 GND GND GND GND No difference

Table 4: Pin-out comparison NEO-M8L vs. NEO-M8U

☞ For software migration and an overall description of the module software operation, see the

u-blox

8 / u-blox M8 Receiver Description Including Protocol Specification

[2].

In NEO-M8L documentation prior to firmware ADR 4.00 the pin 14 name was ANT_ON. The functionality of the pin 14 remains

the same, keeping the backward compatibility.

In NEO-M8L documentation prior to firmware ADR 4.00 pin name was NC.

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5 Product handling

5.1 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

NEO-M8U Data Sheet

[1].

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.

5.2 Soldering

Soldering paste

Use of "No Clean" soldering paste is highly recommended, as it does not require cleaning after the soldering process has taken place. The paste listed 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 section 2.3

The final choice of the soldering paste depends on the approved manufacturing procedures. The paste-mask geometry for applying soldering paste should meet the recommendations.

☞ The quality of the solder joints on the connectors (’half vias’) should 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 be generated. Conversely, if performed excessively, fine balls and large balls will be generated 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 (solder becomes more brittle) of the solder and possible mechanical tensions in the products. Controlled cooling helps to achieve bright solder fillets with a good shape and low contact angle.

• Temperature fall rate: max 4 °C/s

☞ To avoid falling off, the NEO-M8U module should be placed on the topside of the motherboard

during soldering.

The final soldering temperature chosen at the factory depends on additional external factors like choice of soldering paste, size, thickness and properties of the base board, etc. Exceeding the maximum soldering temperature in the recommended soldering profile may permanently damage the module.

Figure 11: Recommended soldering profile

☞ NEO-M8U modules must not be soldered with a damp heat process.

Optical inspection

After soldering the NEO-M8U module, consider an optical inspection step to check that:

• 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 to nearby pad stacks and vias

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 in 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 NEO-M8U modules. The NEO-M8U module should not be submitted to two reflow cycles on a board populated with components on both sides in order to avoid upside down orientation during the second reflow cycle. In this case, the module should always be placed on that side of the board, which is submitted into the last reflow cycle. The reason for this (besides others) is the risk of the module falling off due to the significantly higher weight in relation to other components.

Two reflow cycles can be considered by excluding the above described upside down scenario and taking into account the rework conditions described in section Product handling

☞ Repeated reflow soldering processes and soldering the module upside down are not

recommended.

Wave soldering

Base boards 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 NEO-M8U 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 (e.g. pins 1 and 15), and then continue from left to right.

Rework

The NEO-M8U 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. In general, we do not recommend using a hot air gun because this 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, e.g. 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 NEO-M8U 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, care is required in 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 NEO-M8U module before implementing this 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 makes no warranty for damages to the NEO-M8U 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 etc.) may cause damage to the GNSS Receiver.

☞ u-blox offers no warranty against damages to the NEO-M8U module caused by any Ultrasonic

Processes.

5.3 EOS/ESD/EMI precautions

When integrating GNSS positioning modules into wireless systems, careful consideration must be given to electromagnetic and voltage susceptibility issues. 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 are provided to help 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

NEO-M8U Data Sheet

[1]).

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 an EPA is that there are no highly charging materials near ESD sensitive electronics, all conductive materials are grounded, 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, the following measures should be taken into account whenever handling the receiver.

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•

Unless there is a galvanic coupling between the local GND

(i.e. the work table) and the PCB GND, then 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 (e.g. 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 non ESD

prote

cted 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).

⚠ 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

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, then additional ESD measures can also avoid failures in the field as shown in Figure 12.

Small passive antennas (<2 dBic and performance critical)

Passive antennas (>2 dBic or performance sufficient)

Active antennas

RF_IN

GNSS

Receiver

LNA

RF_IN

GNSS

Receiver

RF_IN

GNSS

Receiver

LNA with appropriate ESD rating

Figure 12: ESD Precautions

☞ Protection measure A is preferred because it offers the best GNSS performance and best level of

ESD protection.

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Electrical Overstress (EOS)

Electrical Overstress (EOS) usually describes situations when the maximum input power exceeds the maximum specified ratings. EOS failure can happen if RF emitters are close to a GNSS receiver or its 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 (e.g. 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 be exceeded, employ EOS protection measures to prevent overstress damage.

For robustness, EOS protection measures as shown in Figure 13 are recommended for designs combining wireless communication transceivers (e.g. GSM, GPRS) and GNSS in the same design or in close proximity.

Small passive antennas (<2 dBic and performance critical)

Passive antennas (>2 dBic or performance sufficient)

Active antennas (without internal filter which need the module antenna supervisor circuits)

RF_IN

GNSS

Receiver

LNA

GPS

Ba ndpass

Filtler

RF_IN

GNSS

Receiver

GPS

Ba ndpass

Filtler

LNA with appropriate ESD rating and maximum input power

GNSS Band pass Filter: SAW or Ceramic with low insertion loss and appropriate ESD rating

Figure 13: 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 (e.g. pin rows etc.)

• Weakly shielded lines on PCB (e.g. on top or bottom layer and especially at the border of a PCB)

• Weak GND concept (e.g. 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 ) into any unshielded PCB lines connected to the GNSS receiver. Place the resistor as close as possible to the GNSS receiver pin.

Alternatively, feed-thru capacitors with good GND connection can be used to protect e.g. the VCC supply pin against EMI. A selection of feed-thru capacitors is listed in Table 5.

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5.4 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 Data Sheet for the absolute maximum power input at the GNSS receiver.

☞ See the GPS Implementation and Aiding Features in u-blox wireless modules [6].

Isolation between GNSS and cellular antennas

In multi-antenna designs, an isolation of approximately 20 dB can be reached with careful placement of the antennas. If such isolation cannot be achieved, e.g. in the case of an integrated cellular antenna, an additional input filter is needed on the GNSS side to block the high energy emitted by the cellular transmitter. Examples of these kinds of filters would be the 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, e.g. GPS frequency of 1575 MHz (see

Figure 14). Such interference signals are typically caused

by harmonics from displays, micro-controller, bus systems, etc.

1525 1550 1625

GPS input filte r cha rac teris tics

1575 1600

-110

Jammi n g signal

1525

1550 1625

Frequency [MHz]

Power [dBm]

GPS input filte r cha rac teris tics

1575 1600

Jammi ng

signal

GPS

signals

GPS Car ri er

1575.4 MHz

Figure 14: In-band interference signals

Figure 15: In-band interference sourcesMeasures against in-band interference include:

• 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

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Out-band interference

Out-band interference is caused by signal frequencies that are different from the GNSS carrier (see Figure 16). The main sources are wireless communication systems such as GSM, CDMA, WCDMA, Wi-Fi, BT, etc.

Figure 16: 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 5) into the antenna input line

to the GNSS receiver (see Figure 17).

Figure 17: Measures against out-band interference

☞ For design-in recommendations in combination to Cellular operation see the appendix.

☞ See the GPS Implementation and Aiding Features in u-blox wireless modules [6].

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Appendix

A Glossary

Recommended parts

Recommended parts are selected on data sheet basis only. Other components may also be used.

Part Manufacturer Parts ID Remarks Parameters to consider

Diode Semiconductor

ON 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-B8401-P810 GPS+GLONASS High attenuation

B3913: B39162B3913U410 GPS+GLONASS+BeiDou For automotive application

B4310: B39162B4310P810 GPS+GLONASS Compliant to the AEC-Q200 standard

ReyConns NDF9169 GPS+ BeiDou Low insertion loss, Only for mobile

application

Murata SAFFB1G56KB0F0A GPS+GLONASS+BeiDou Low insertion loss, Only for mobile

application

SAFEA1G58KB0F00 GPS+GLONASS Low insertion loss, only for mobile

application

SAFEA1G58KA0F00 GPS+GLONASS High attenuation, only for mobile

application

SAFFB1G58KA0F0A GPS+GLONASS High attenuation, only for mobile

application

SAFFB1G58KB0F0A GPS+GLONASS Low insertion loss, Only for mobile

application

TAI-SAW TA1573A GPS+GLONASS Low insertion loss

TA1343A GPS+GLONASS+BeiDou Low insertion loss

TA0638A GPS+GLONASS+BeiDou Low insertion loss

LNA JRC NJG1143UA2 LNA Low noise figure, up to 15 dBm RF

input power

Inductor Murata LQG15HS27NJ02 L, 27 nH

Impedance @ freq GPS > 500 Ω

Capacitor Murata GRM1555C1E470JZ01 C, 47 pF DC-block

Ferrite bead

Murata BLM15HD102SN1 FB High IZI @ fGSM

Feed thru

capacitor for signal

Murata NFL18SP157X1A3

Monolithic Type Array Type

Load Capacitance appropriate to Baud rate

CL < xxx pF

NFA18SL307V1A45

Feed thru

capacitor

Murata NFM18PC ….

NFM21P….

0603 2A 0805 4A

Resistor

10 Ω ± 10%, min 0.250 W

bias

560 Ω ± 5%

100 kΩ ± 5%

R3, R4

Table 5: Recommended parts

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Recommended parts

Manufacturer Order No. Comments

Hirschmann (www.hirschmann-car.com) GLONASS 9 M GPS+GLONASS active

Taoglas (www.taoglas.com) AA.160.301111 36*36*4 mm, 3-5V 30mA active

Taoglas (www.taoglas.com) AA.161.301111 36*36*3 mm, 1.8 to 5.5V / 10mA at 3V active

INPAQ (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 35x35x3 mm GPS+GLONASS passive

Amotech (www.amotech.co.kr) A25-4102920-2J3 25x25x4 mm GPS+GLONASS passive

Amotech (www.amotech.co.kr) A18-4135920-AMT04 18x18x4 mm GPS+GLONASS passive

INPAQ (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 6: Recommended antennas

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u-blox NEO-M8U, NEO-M8U-04B-00, NEO-M8L Hardware Integration Manual

Specifications and Main Features

Frequently Asked Questions

User Manual