Integration Manual

TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R04 Advance Information Design-in
Page 104 of 141
Connection with u-blox 3.0 V GNSS receivers
Figure 59 shows an application circuit for connecting TOBY-L2 cellular modules to a u-blox 3.0 V GNSS receiver:
 As the SDA and SCL pins of the TOBY-L2 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 with proper pull-up resistors (e.g. the TI TCA9406 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).
 As the GPIO3 and GPIO4 pins of the TOBY-L2 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).
 A pull-down resistor is mounted on GPIO2 line to avoid an improper switch on of the u-blox GNSS receiver.
 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.
TOBY-L2 series
(except TOBY-L2x0-00S)
u-blox GNSS
3.0 V receiver
24
GPIO3
25
GPIO4
1V8
B1 A1
GND
U3
B2A2
VCCBVCCA
Unidirectional
Voltage Translator
C4
C5
3V0
TxD1
EXTINT0
R1
INOUT
GND
GNSS LDO
Regulator
SHDN
R2
VMAIN3V0
U1
22
GPIO2
55
SDA
54
SCL
R4 R5
1V8
SDA_A SDA_B
GND
U2
SCL_ASCL_B
VCCA
VCCB
I2C-bus Bidirectional
Voltage Translator
2
V_INT
C1
C2
C3
R3
SDA2
SCL2
VCC
DIR1
DIR2
3
V_BCKPV_BCKP
OE
OE
GNSS data ready
GNSS RTC sharing
GNSS supply enabled
Figure 59: Application circuit for connecting TOBY-L2 modules to u-blox 3.0 V GNSS receivers
Reference
Description
Part Number - Manufacturer
R1, R2, R4, R5
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, C4, C5
100 nF Capacitor Ceramic X5R 0402 10% 10V
GRM155R71C104KA01 - Murata
U1, C1
Voltage Regulator for GNSS receiver and capacitor
related output bypass
See GNSS receiver Hardware Integration Manual
U2
I2C-bus Bidirectional Voltage Translator
TCA9406DCUR - Texas Instruments
U3
Generic Unidirectional Voltage Translator
SN74AVC2T245 - Texas Instruments
Table 38: Components for connecting TOBY-L2 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 GNSS
Implementation Application Note [13] and the Hardware Integration Manual of the u-blox GNSS receivers.