LENA-R8 series - System integration manual
UBX-22015376 - R02
Design-in
Page 88 of 116
C1-Public
2.9
Reserved pins (RSVD)
LENA-R8 series modules have pins reserved for future use, named
RSVD
: they can all be left
unconnected on the application board.
2.10
GNSS power management
☞
LENA-R8001 modules do not include a GNSS receiver: GNSS power management is not available.
2.10.1
GNSS supply input (VCC_GNSS)
Connecting an external DC power supply at the
VCC_GNSS
input is necessary for normal operations
of the LENA-R8001M10 GNSS system, considering
VCC_GNSS
pin provides power to the GNSS RF
domains and internal LNA, the GNSS system core, the GNSS digital peripheral I/O, the dedicated
TCXO through an integrated LDO regulator, as is illustrated in
Voltage at
VCC_GNSS
must be clean, stable, and tight at 1.8 V to properly supply the GNSS system.
During operation, the current drawn by the GNSS system may vary. For this reason, it is important
that the supply circuitry is able to support the peak power for a short time.
External circuits using linear LDO regulators or DC/DC switching regulators can be implemented to
provide the clean, stable, and tight 1.8 V supply at the
VCC_GNSS
input.
External
Supply
LENA-R8001M10
VCC_ GNSS
99
GND
1V8
100nF
Figure 67: Application circuit for LENA-R8001M10 modules GNSS system supply using external 1.8 V supply system
☞
Do not add series resistance greater than 0.2 Ω
along the
VCC_GNSS
supply line, to avoid voltage
ripple due to the dynamic current conditions.
☞
The voltage supply ramp at the
VCC_GNSS
input
must not exceed the minimum specified voltage
ramp. Otherwise, the receiver might get damaged.
☞
For more information about
VCC_GNSS
voltage range, voltage ramp and current consumption
characteristics to appropriately select and design an external supply circuit, see the LENA-R8
series data sheet
☞
For more information and examples about GNSS main supply external circuit guidelines, see the
u-blox M10 standard precision GNSS chip data sheet
illustrates an alternative solution using the
V_INT
1.8 V supply output of the cellular system,
generated by an internal linear LDO regulator, to supply the
VCC_GNSS
input of LENA-R8001M10
GNSS system instead of using an external voltage regulator. The
V_INT
1.8 V supply output of the
cellular module can sustain the maximum current consumption of LENA-R8001M10 GNSS system.
The internal linear LDO regulator generating the
V_INT
supply is enabled when the cellular system is
switched on, and it is disabled when the cellular system is switched off: using the circuit in
the GNSS system will result not supplied when the cellular system is switched off.