SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11
Design-in
Page 110 of 157
the GNSS 3.0 V supply can be ramped up before the
V_INT
1.8 V cellular supply). External pull-up
resistors are not needed on the cellular module side, as they are already integrated in the cellular
module.
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.
The
GPIO3
pin is connected to the
TXD1
pin of the u-blox 3.0 V GNSS receiver providing the additional
“GNSS Tx data ready” function, 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.
u-blox GNSS
3.0 V receiver
24
GPIO3
1V8
B1
A1
GND
U3
B2
A2
VCCB
VCCA
Unidirect ional
Volt age Translat or
C4
C5
3V0
TxD1
R1
IN
OUT
LDO Regulat or
SHDNn
R2
VM AIN
3V0
U1
23
GPIO2
26
SDA
27
SCL
1V8
SDA_A
SDA_B
GND
U2
SCL_A
SCL_B
VCCA
VCCB
I2C-bus Bidirect ional
Volt age Translat or
4
V_INT
C1
C2
C3
R3
SDA2
SCL2
VCC
DIR1
DIR2
OEn
OE
GNSS dat a ready
GNSS supply enabled
GND
SARA-R4/ N4
(except ‘0 0 ’,’0 1’ versions)
Figure 52: Application circuit for connecting SARA-R4/N4 series modules to u-blox 3.0 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
C2, C3, C4, C5
100 nF Capacitor Ceramic X5R 0402 10% 10V
GRM155R71C104KA01 - Murata
U1, C1
Voltage Regulator for GNSS receiver and related
output bypass capacitor
See GNSS receiver Hardware Integration Manual
U2
I2C-bus Bidirectional Voltage Translator
TCA9406DCUR - Texas Instruments
U3
Generic Unidirectional Voltage Translator
SN74AVC2T245 - Texas Instruments
Table 35: Components for connecting SARA-R4/N4 series modules to u-blox 3.0 V GNSS receivers
For additional guidelines regarding the design of applications with u-blox 3.0 V GNSS receivers see the
Hardware Integration Manual of the u-blox GNSS receivers.
