u-blox LARA-R2 series System Integration Manual page 110

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

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.
u-blox GNSS
1.8 V receiver
V_BCKP
VCC
SDA2
SCL2
TxD1
EXTINT0
Figure 60: Application circuit for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers
Reference Description
R1, R2 4.7 kΩ Resistor 0402 5% 0.1 W
R3 47 kΩ Resistor 0402 5% 0.1 W
U1 Voltage Regulator for GNSS receiver
Table 44: Components for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers
UBX-16010573 - R02
2
C pins of the cellular module.
GNSS LDO
1V8
Regulator
OUT IN
SHDN
C1
1V8 1V8
GND
U1
R1 R2
Objective Specification
LARA-R2 series - System Integration Manual
LARA-R2 series
(except '02' product version)
V_BCKP
2
VMAIN
GNSS supply enabled
23 GPIO2
R3
26 SDA
SCL
27
GNSS data ready
GPIO3
24
GNSS RTC sharing
GPIO4
25
Part Number - Manufacturer
RC0402JR-074K7L - Yageo Phycomp
RC0402JR-0747KL - Yageo Phycomp
See GNSS receiver Hardware Integration Manual
Design-in
Page 110 of 148