NEO-M9N-Integration manual
Avoid high resistance on the V_BCKP line: During the switch from main supply to backup
supply, a short current adjustment peak can cause a high voltage drop on the pin with
possible malfunctions.
If no backup supply voltage is available, connect the V_BCKP pin to VCC.
Allow all I/O including UART and other interfaces to float or connect to a high impedance in
HW backup mode (V_BCKP supplied when VCC is removed). See the Interfaces section. It
is essential that the interfaces and PIOs are isolated with open-drain buffers when VCC is
removed to prevent the chip from being powered through these circuits.
In software backup mode the receiver remains supplied and backup is handled with software
commands. See the NEO-M9N Interface description [2] for more information.
4.2.3 V_USB: USB interface power supply
V_USB supplies the USB interface. If the USB interface is not used, the V_USB pin must be connected
to GND. For more information about correctly handling the V_USB pin, see Interfaces section.
4.3 NEO-M9N minimal design
The minimal electrical circuit for NEO-M9N operation using the UART1 interface is shown in Figure
31 below.
Figure 31: Minimal NEO-M9N design
For a minimal design with the NEO-M9N GNSS modules, the following functions and pins should be
considered:
• Connect the power supply to VCC and V_BCKP.
• If hot or warm start operations are needed, connect a backup battery to V_BCKP.
• If USB is not used connect V_USB to ground.
• Ensure an optimal ground connection to all ground pins of the NEO-M9N GNSS module.
UBX-19014286 - R07
4 Design Page 71 of 95
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