Ublox SARA-G300 - Page 147

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26 Design-in
Page 147 of 217
Connection with u-blox 3.0 V GNSS receivers
Figure 81 shows an application circuit example for connecting a SARA-G340 or a SARA-G350 cellular module to
a u-blox 3.0 V GNSS receiver:
 The SDA and SCL pins of SARA-G340 / SARA-G350 are directly connected to the related pins of the u-blox
3.0 V GNSS receiver, with appropriate pull-up resistors connected to the 3.0 V GNSS supply enabled after
the V_INT supply of the I
2
C pins of the cellular module. An I
2
C-bus Voltage Translator is not needed because
the SARA-G340 / SARA-G350 DDC (I
2
C) pins are capable up to 3.3 V.
 The GPIO2 is connected to the active-high enable pin of the voltage regulator that supplies the u-blox 3.0 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.
 As the GPIO3 and GPIO4 pins of SARA-G340 / SARA-G350 cellular modules are not tolerant up to 3.0 V,
the connection to the related pins of the u-blox 3.0 V GNSS receiver must be provided using a suitable
Unidirectional General Purpose Voltage Translator (e.g. TI SN74AVC2T245, which additionally provides the
partial power down feature so that the 3.0 V GNSS supply can be also ramped up before the V_INT 1.8 V
cellular supply).
 The V_BCKP supply output of SARA-G340 / SARA-G350 is directly connected to the V_BCKP backup supply
input pin of the u-blox 3.0 V GNSS receiver as in the application circuit for a u-blox 1.8 V GNSS receiver.
u-blox GNSS
3.0 V receiver
24
GPIO3
1V8
B1 A1
GND
U3
B2A2
VCCBVCCA
Unidirectional
Voltage Translator
C4
C5
3V0
TxD1
R1
INOUT
GNSS LDO Regulator
SHDNn
R2
VMAIN3V0
U1
23
GPIO2
26
SDA
27
SCL
C1
R3
SDA2
SCL2
VCC
DIR1
DIR2
2
V_BCKPV_BCKP
OEn
GNSS data ready
GNSS supply enabled
GND
SARA-G340 / SARA-G350
EXTINT0 GPIO4
25
GNSS RTC sharing
Figure 81: Application circuit for connecting SARA-G3 modules to u-blox 3.0 V GNSS receivers
Reference
Description
Part Number – Manufacturer
R1, R2
4.7 kΩ Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
R3
47 kΩ Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
C2, C3
100 nF Capacitor Ceramic X5R 0402 10% 10V
GRM155R71C104KA01 - Murata
U1
Voltage Regulator for GNSS receiver
See GNSS receiver Hardware Integration Manual
U2
Generic Unidirectional Voltage Translator
SN74AVC2T245 - Texas Instruments
Table 52: Components for connecting SARA-G3 modules to u-blox 3.0 V GNSS receivers