u-blox EVA-M8M, Hardware Integration Manual

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EVA-M8M - Hardware Integration Manual
UBX-14006179 - R02 Early Production Information Design-in
Page 18 of 45
2.8 Design-in checklist
2.8.1 General considerations
Check power supply requirements and schematic:
 Is the power supply voltage within the specified range? See how to connect power in Section 2.1.
 For USB devices: Is the voltage
V_USB
voltage within the specified range? Do you have a Bus or Self
powered setup?
 Compare the peak current consumption of EVA-M8M series with the specification of your power supply.
 GNSS receivers require a stable power supply. Avoid series resistance in your power supply line (the line to
VCC
) to minimize the voltage ripple on
VCC
.
Backup battery

For achieving a minimal Time To First Fix (TTFF) after a power down (warm starts, hot starts), make sure to
connect a backup battery to
V_BCKP , and use an RTC. If not used, make sure V_BCKP is connected to
VCC_IO .
Antenna/ RF input
 The total noise figure including external LNA (or the LNA in the active antenna) should be around 1 dB.
 With the EVA-M8M series, an external LNA is mandatory if no active antenna is used to achieve the
performance values as written in the
EVA-M8M Data Sheet
[1].
 Make sure the antenna is not placed close to noisy parts of the circuitry and not facing noisy parts. (e.g.
micro-controller, display, etc.)

To optimize performance in environments with out-band jamming/interference sources, use an additional
SAW filter.
For more information dealing with interference issues see the GPS Antenna Application Note [3].
Schematic
 Inner pins of the package must all be connected to GND.
2.8.2 Schematic design-in for EVA-M8M
For a minimal design with the EVA-M8M the following functions and pins need to be considered:
•
Connect the power supply to VCC , VCC_IO and V_BCKP .
•
V_USB
: Connect the USB power supply to a LDO before feeding it to
V_USB
and
VCC
or connect it to GND
if USB is not used.
•
Ensure an optimal ground connection to all ground pins of the EVA-M8M modules
•
Choose the required serial communication interfaces (UART, USB, SPI or DDC) and connect the appropriate
pins to your application
•
If you need hot or warm start in your application, connect a Backup Battery to V_BCKP and add RTC circuit.
•
If antenna bias is required, see Appendix A.4.