LARA-R2 series - System Integration Manual
UBX-16010573 - R02
Objective Specification
Design-in
Page 110 of 148
Connection with u-blox 1.8 V GNSS receivers
Figure 60 shows an application circuit for connecting the cellular module to a u-blox 1.8 V GNSS receiver:
The
SDA
and
SCL
pins of the cellular module are directly connected to the related pins of the u-blox 1.8 V
GNSS receiver, with appropriate pull-up resistors connected to the 1.8 V GNSS supply enabled after the
V_INT
supply of the I
2
C pins of the cellular module.
The
GPIO2
pin is connected to the active-high enable pin of the voltage regulator that supplies the u-blox
1.8 V GNSS receiver providing the “GNSS supply enable” function. A pull-down resistor is provided to avoid
a switch on of the positioning receiver when the cellular module is switched off or in the reset state.
The
GPIO3
and
GPIO4
pins are directly connected respectively to
TXD1
and
EXTINT0
pins of the u-blox
1.8 V GNSS receiver providing “GNSS Tx data ready” and “GNSS RTC sharing” functions.
The
V_BCKP
supply output of the cellular module is connected to the
V_BCKP
backup supply input pin of
the GNSS receiver to provide the supply for the GNSS real time clock and backup RAM when the
VCC
supply
of the cellular module is within its operating range and the
VCC
supply of the GNSS receiver is disabled. This
enables the u-blox GNSS receiver to recover from a power breakdown with either a hot start or a warm start
(depending on the actual duration of the GNSS
VCC
outage) and to maintain the configuration settings
saved in the backup RAM.
R1
IN
OUT
GND
GNSS LDO
Regulator
SHDN
u-blox GNSS
1.8 V receiver
SDA2
SCL2
R2
1V8
1V8
VMAIN
1V8
U1
23
GPIO2
SDA
SCL
C1
TxD1
EXTINT0
GPIO3
GPIO4
26
27
24
25
VCC
R3
V_BCKP
V_BCKP
2
GNSS data ready
GNSS RTC sharing
GNSS supply enabled
LARA-R2 series
(except ‘02’ product version)
Figure 60: Application circuit for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers
Reference
Description
Part Number - Manufacturer
R1, R2
4.7 k
Ω
Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
R3
47 k
Ω
Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
U1
Voltage Regulator for GNSS receiver
See GNSS receiver Hardware Integration Manual
Table 44: Components for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers