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LEA-M8F 

u-blox M8 time and frequency reference 
GNSS module 

Hardware Integration Manual

 

 
 
 
 
 

 
 
 
 
 
 
 
 

Abstract

 

This document describes the hardware  features and design-in 
aspects for the LEA-M8F time and frequency reference module. This 
device incorporates  the u-blox  M8  concurrent  GNSS IC  that can 
receive GPS, GLONASS, BeiDou and QZSS signals. It provides a low 
phase noise 30.72MHz system reference oscillator disciplined by 
GNSS, a precise and jitter-free time-pulse and features high 
sensitivity signal acquisition and single satellite timing with 
automatic hold over during signal outage. 

 

www.u-blox.com

 

UBX-14000034 - R03 

Summary of Contents for LEA-M8F

Page 1: ...rence module This device incorporates the u blox M8 concurrent GNSS IC that can receive GPS GLONASS BeiDou and QZSS signals It provides a low phase noise 30 72MHz system reference oscillator disciplin...

Page 2: ...ucts Product name Type number ROM FLASH version PCN reference LEA M8F LEA M8F 0 00 FLASH FW2 20 FTS1 01 N A u blox reserves all rights to this document and the information contained herein Products na...

Page 3: ...10 1 6 1 RESET_N 10 1 6 2 D_SEL 10 1 6 3 FREQ_PHASE_IN0 EXINT0 FREQ_PHASE_IN1 EXTINT1 11 1 6 4 REF_FREQ_OUT 11 1 6 5 TIMEPULSE TP2 11 1 7 Device Configuration 11 2 Design 12 2 1 Layout Footprint and...

Page 4: ...3 Early Production Information Contents Page 4 of 30 4 3 EOS ESD EMI precautions 23 4 4 Applications with cellular modules 26 Appendix 28 Recommended parts 28 Manufacturer 28 Order No 28 Comments 28 R...

Page 5: ...d providing 100 ppb autonomous hold over An external TCXO or OCXO can also be measured and controlled for TD LTE LTE Advanced and other applications requiring extended hold over External sources of sy...

Page 6: ...schematic view of the module s internal organization Figure 1 LEA M8F Block Diagram The device contains all the elements required to implement a multi GNSS frequency and time synchronization system It...

Page 7: ...med as TX ready for DDC interface Leave open if not used RxD1 MOSI 4 I Serial Port 1 or SPI Data o p Communication interface i p dependent on D_SEL with internal pull up resistor to VCC Leave open if...

Page 8: ...Receiver Transmitter UART serial interface RxD TxD supporting configurable baud rates See the LEA M8F Data Sheet 1 for the supported baud rates The signal input and output levels are 0 V to VCC with...

Page 9: ...ent 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 wh...

Page 10: ...er combination connected to a VCTCXO VCOCXO Note that 12 bit DAC may not provide sufficient resolution if used over the full circuit voltage range and hence may compromise the controlled frequency per...

Page 11: ...the module s disciplined 30 72MHz VCTCXO CMOS buffer via on module resistor 1 6 5 TIMEPULSE TP2 The timepulse signal is output from this pin This pin is the standard u blox M8 TP2 output hence all tim...

Page 12: ...ldering of the customer 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 Stencil 150 m 15 7 mm 618 mil 17...

Page 13: ...eet 1 2 1 2 Antenna connection and ground plane design The LEA M8F module can be connected to passive patch or active antennas The RF connection is on the PCB and connects the RF_IN pin with the anten...

Page 14: ...or fill with ground planes H H Figure 8 PCB build up for micro strip line Left 2 layer PCB right 4 layer PCB General design recommendations The length of the micro strip line should be kept as short...

Page 15: ...tion for printed circuit boards The basic configuration is shown in Figure 10 and Figure 11 As a rule of thumb for an FR 4 material the width of the conductor is roughly double the thickness of the di...

Page 16: ...onents 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 pi...

Page 17: ...ltage at VCC_RF to supply the antenna DC power The V_ANT pin provides a current limited supply connection to the RF_IN pin for antenna LNA biasing see Figure 13 below Figure 13 Active antenna design e...

Page 18: ...he u blox support team to ensure the compatibility of key functionalities 3 1 Software migration For an overall description of the module software operation see the u blox M8 Receiver Description incl...

Page 19: ...ply V_BCKP Backup voltage supply Back up operation not supported Connect to Vcc 12 SAFEBOOT_ N GND Reserved Leave Open Test point for service access 13 GND GND GND GND No difference 14 GND GND GND GND...

Page 20: ...s 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 hea...

Page 21: ...oldering 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...

Page 22: ...th a cross diagonal fixture soldering e g pins 1 and 15 and then 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 g...

Page 23: ...rve 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 LEA M8F Data Sheet 0 Electrostatic discharge...

Page 24: ...tection 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 follow...

Page 25: ...SD rating Figure 17 EOS and ESD Precautions Electromagnetic interference EMI Electromagnetic interference EMI is the addition or coupling of energy originating from any RF emitting device This can cau...

Page 26: ...chieved e g in the case of an integrated GSM 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 filte...

Page 27: ...at are different from the GNSS carrier see Figure 21 The main sources are wireless communication systems such as GSM CDMA WCDMA Wi Fi BT etc 0 500 1000 1500 2000 GPS input filter characteristics 0 110...

Page 28: ...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 DAC TI DAC8571 Osc Control Volt...

Page 29: ...tion Version 2 1 Jan 2000 http www nxp com acrobat_download literature 9398 39340011_21 pdf 9 GPS Implementation and Aiding Features in u blox wireless modules Docu No GSM G1 CS 09007 For regular upda...

Page 30: ..._ap u blox com Support support_ap u blox com Regional Office Australia Phone 61 2 8448 2016 E mail info_anz u blox com Support support_ap u blox com Regional Office China Beijing Phone 86 10 68 133 54...

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