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GNSS Module Application Notes (MT3333 series)
Table of Contents
Table of Contents .......................................................................................................................3
Attention ...................................................................................................................................4
Technical Support.......................................................................................................................5
1. Introduction ...........................................................................................................................6
2. General Rules for Design-in.....................................................................................................8
2.1 Circuit Design....................................................................................................... 8
2.1.1 Power supply VCC .................................................................................................................. 8
2.1.2 VBACKUP backup battery....................................................................................................... 9
2.1.3 UART / I2C/ SPI Serial Interface ........................................................................................... 10
(a) UART 0 (RX/TX) ........................................................................................................................ 10
(b) I2C (SCL/SDA)........................................................................................................................... 10
(c) SPI (CS/CLK/MISO/MOSI)......................................................................................................... 11
2.1.4 GND-Ground ........................................................................................................................ 11
2.1.5 Antenna Compliance Design................................................................................................ 12
2.1.6 1PPS ..................................................................................................................................... 16
2.1.7 3D_Fix .................................................................................................................................. 17
2.2 Layout Guideline................................................................................................ 19
2.2.1 Layout underneath the GNSS module ................................................................................. 19
2.2.2 Keep far away from high profile or metal canned components......................................... 21
2.2.3 Placement ............................................................................................................................ 23
2.2.4 Trace..................................................................................................................................... 23
2.2.5 Ground Segmentation.......................................................................................................... 24
2.2.6 Ground Plane ....................................................................................................................... 24
2.2.7 Metal effect on the GNSS module ....................................................................................... 27
3. Thermal Profile for SMD Modules.........................................................................................28
4. Troubleshooting ...................................................................................................................30
5. Contact.................................................................................................................................32
Appendix I: Super Capacitor Design ..........................................................................................33
Appendix II: 50 Ω Antenna Matching ........................................................................................34
Appendix III: UART to RS232 Interface ......................................................................................35
Appendix IV: UART to USB Interface .........................................................................................36
Appendix V: How to efficiently transfer 1PPS through extended distances................................. 37
Appendix VI: Caution for Reflow Soldering Process ...................................................................42
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