LENA-R8 series - System integration manual
UBX-22015376 - R02
Design-in
Page 82 of 116
C1-Public
Connection with u-blox 1.8 V GNSS receivers (LENA-R8001 modules only)
shows an application circuit for connecting the 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 I2C 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 GNSS when the module is switched off.
•
The
GPIO3
pin is directly connected to the pin of the u-blox 1.8
V GNSS receiver providing “GNSS
Tx data ready” function.
IN
OUT
GND
GNSS LDO
Regulator
SHDN
u-blox M10 GNSS
1.8 V receiver
SDA
SCL
VMAIN
1V8
U1
23
GPIO2
SDA
SCL
C1
26
27
VCC
R1
GNSS supply enabled
LENA-R8001
TxD
GPIO3
24
GNSS Tx data ready
GND
GND
R3
R2
Figure 62: Application circuit for connecting LENA-R8001 modules to u-blox 1.8 V GNSS receivers
Reference
Description
Part number - manufacturer
R1
47 k
Resistor
Various Manufacturers
R2, R3
10 k
Resistor
Various Manufacturers
U1, C1
Voltage Regulator for GNSS receiver and related
output bypass capacitor
See GNSS receiver Hardware Integration Manual
Table 43: Components for connecting LENA-R8001 modules to u-blox 1.8 V GNSS receivers
illustrates an alternative solution as a supply circuit for u-blox 1.8 V GNSS receivers, using
the
V_INT
1.8 V supply output of the cellular module, generated by an internal linear LDO regulator, to
supply an external u-blox 1.8 V GNSS receiver instead of using an external voltage regulator as in the
previous
. The
V_INT
1.8 V supply output of the cellular module can sustain the maximum
current consumption of the u-blox 1.8 V GNSS receivers.
The internal linear LDO regulator that generates the
V_INT
supply is set to 1.8 V (typical) when the
cellular module is switched on, and it is disabled when the cellular module is switched off: in such case,
implementing the circuit illustrated in
, the external u-blox 1.8 V GNSS receiver will result
not supplied when the cellular module is switched off.
In the application circuit example illustrated in
, the supply of the u-blox 1.8 V GNSS receiver
is switched on/off using an external p-channel MOSFET controlled by the
GPIO2
output of the cellular
module by means of a proper inverting transi
stor, implementing the “GNSS supply enable” function.
u-blox M10 GNSS
1.8 V receiver
SDA
SCL
SDA
SCL
26
27
LENA-R8001
TxD
GPIO3
24
GNSS Tx data ready
GND
GND
23
GPIO2
VCC
1V8
C1
R1
4
V_INT
R3
R2
T2
T1
GNSS supply enabled
R5
R4
Figure 63: Application circuit for connecting LENA-R8001 modules to u-blox 1.8 V GNSS receivers using V_INT as supply
