Ublox LISA-U100, Integration Manual

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LISA-U series - System Integration Manual
UBX-13001118 - R17 Advance information System description
Page 92 of 190
Connection with u-blox 3.0 V GNSS receivers
Figure 50 shows an application circuit for connecting a LISA-U cellular module to a u-blox 3.0 V GNSS receiver:

As the
SDA
and
SCL
pins of the LISA-U cellular module are not tolerant up to 3.0 V, the connection to the
related I 2 C pins of the u-blox 3.0 V GNSS receiver must be provided using a proper I 2 C-bus Bidirectional
Voltage Translator (e.g. TI TCA9406, which additionally provides the partial power down feature so that the
GNSS 3.0 V supply can be ramped up before the
V_INT 1.8 V cellular supply), with proper pull-up resistors.

As the
GPIO3
and
GPIO4
pins of the LISA-U cellular module 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 proper 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 the cellular module can be directly connected to the
V_BCKP
backup supply
input pin of the GNSS receiver as in the application circuit for a u-blox 1.8 V GNSS receiver.
LISA-U series
(except LISA-U200-00S)
u-blox GNSS
3.0 V receiver
23
GPIO3
24
GPIO4
1V8
B1 A1
GND
U3
B2 A2
VCCB VCCA
Unidirectional
Voltage Translator
C4
C5
3V0
TxD1
EXTINT0
R1
IN OUT
GND
GPS LDO
Regulator
SHDN
R2
VMAIN 3V0
U1
21
GPIO2
46
SDA
45
SCL
R4 R5
1V8
SDA_A SDA_B
GND
U2
SCL_A SCL_B
VCCA VCCB
I2C-bus Bidirectional
Voltage Translator
4
V_INT
C1
C2 C3
R3
SDA2
SCL2
VCC
DIR1
DIR2
2
V_BCKP V_BCKP
OE
R7
OE
Figure 50: DDC Application circuit for u-blox 3.0 V GNSS receiver
Reference Description Part Number - Manufacturer
R1, R2, R4, R5, R7 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 40: Components for DDC application circuit for u-blox 3.0 V GNSS receiver