NEO-M9N - Integration manual
Pin no.
Name
I/O
Description
16
Reserved
-
Reserved
17
Reserved
-
Reserved
18
SDA / SPI CS_N
I/O
I2C data if D_SEL = VCC (or open); SPI chip select if D_SEL = GND
19
SCL / SPI SLK
I/O
I2C clock if D_SEL = VCC (or open); SPI clock if D_SEL = GND
20
TXD / SPI MISO
O
UART output if D_SEL = VCC (or open); SPI MISO if D_SEL = GND
21
RXD / SPI MOSI
I
UART input if D_SEL = VCC (or open); SPI MOSI if D_SEL = GND
22
V_BCKP
I
Backup voltage supply
23
VCC
I
Supply voltage
24
GND
I
Ground
Table 25: NEO-M9N pin assignment
4.2 Power supply
The u-blox NEO-M9N module has three power supply pins: VCC, V_BCKP and V_USB.
(The VCC_RF pin is an output pin that can supply an active antenna or external LNA.)
4.2.1 VCC: Main supply voltage
The
VCC
pin is connected to 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 applicable data sheet [
] for
specification).
The module integrates a DC/DC converter, which allows reduced power consumption.
When switching from backup mode to normal operation or at startup, u-blox NEO-M9N
modules must charge the internal capacitors in the core domain. In certain situations, this
can result in a significant current draw. For low-power applications using backup mode, it is
important that the power supply or low ESR capacitors at the module input can deliver this
current/charge.
To reduce peak current during power on, users can employ an LDO that has an in-built
current limiter.
Do not add any series resistance greater than 0.2
Ω
to the VCC supply as it will generate
input voltage noise due to dynamic current conditions.
For the NEO-M9N module the equipment must be supplied by an external limited power
source in compliance with the clause 2.5 of the standard IEC 60950-1.
4.2.2 V_BCKP: Backup supply voltage
The V_BCKP pin can be used to provide power to maintain the real-time clock (RTC) and battery-
backed RAM (BBR) when VCC is removed.
Maintaining time and GNSS orbit data improves the receiver performance at startup. Especially if
the RTC and BBR contents are still current, i.e. after a short VCC outage.
If V_BCKP is not provided, the module performs a cold start at power up.
If a host is connected to NEO-M9N, V_BCKP can be partially emulated by using UBX-UPD-SOS
functionality. BBR data can saved to the host and restored at startup. See the applicable
UBX-19014286 - R07
4 Design
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