Integration Manual

TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R04 Advance Information Design-in
Page 102 of 141
Connection with u-blox 1.8 V GNSS receivers
Figure 57 shows an application circuit for connecting TOBY-L2 cellular modules to a u-blox 1.8 V GNSS receiver.
 SDA / SCL pins of the TOBY-L2 cellular module are directly connected to the relative I
2
C 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 I
2
C pins of the TOBY-L2 cellular module.
 GPIO3 and GPIO4 pins are directly connected respectively to the TxD1 and EXTINT0 pins of the u-blox
1.8 V GNSS receiver to provide “GNSS data ready” and “GNSS RTC sharing” functions.
 A pull-down resistor is mounted on GPIO2 line to avoid an improper switch on of the u-blox GNSS receiver.
 The V_BCKP output of the cellular module is connected to the V_BCKP input pin of the GNSS receiver to
provide the supply for the GNSS RTC and backup RAM when the VCC supply of the cellular module is within
its operating range and the VCC supply of the GNSS receiver is disabled. This enables the u-blox GNSS
receiver to recover from a power breakdown with either a hot start or a warm start (depending on the
duration of the GNSS VCC outage) and to maintain the configuration settings saved in the backup RAM.
TOBY-L2 series
(except TOBY-L2x0-00S)
R1
INOUT
GND
GNSS LDO
Regulator
SHDN
u-blox GNSS
1.8 V receiver
SDA2
SCL2
R2
1V8 1V8
VMAIN1V8
U1
22
GPIO2
SDA
SCL
C1
TxD1
EXTINT0
GPIO3
GPIO4
55
54
24
25
VCC
R3
V_BCKP V_BCKP
3
GNSS data ready
GNSS RTC sharing
GNSS supply enabled
Figure 57: Application circuit for connecting TOBY-L2 modules to u-blox 1.8 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
U1
Voltage Regulator for GNSS receiver
See GNSS receiver Hardware Integration Manual
Table 36: Components for connecting TOBY-L2 modules to u-blox 1.8 V GNSS receivers
Figure 58 illustrates an alternative application circuit solution in which the TOBY-L2 supplies a u-blox 1.8 V GNSS
receiver. The V_INT 1.8 V regulated supply output of a TOBY-L2 module can be used as supply source for a
u-blox 1.8 V GNSS receiver (u-blox 6 generation receiver or newer) instead of using an external voltage
regulator, as shown in Figure 57. The V_INT supply is able to support the maximum current consumption of
these positioning receivers.
The internal switching step-down 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 module is switched off.
The supply of the u-blox 1.8 V GNSS receiver can be switched off using an external p-channel MOS controlled by
the GPIO2 pin of TOBY-L2 cellular modules by means of a proper inverting transistor as shown in Figure 58,
implementing the “GNSS supply enable” function. If this feature is not required, the V_INT supply output can be
directly connected to the u-blox 1.8 V GNSS receiver, so that it will switch on when V_INT output is enabled.