Integration Manual

Table Of Contents
TOBY-L3 series - System Integration Manual
TSD-19090601 - R13 System Integration Manual Page 105 of 143
Table 39: Components for connecting TOBY-L3 series modules to u-blox 1.8 V GNSS devices
Figure 52 illustrates an alternative application circuit solution in which the cellular module supplies a u-blox
1.8 V GNSS device. The V_INT 1.8 V regulated supply output of the cellular module can be used as supply
source for a u-blox 1.8 V GNSS device instead of using an external voltage regulator, as shown in Figure
51. The V_INT supply is able to support the maximum current consumption of these positioning devices.
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 device can be switched off using an external p-channel MOS controlled
by the GPIO2 pin of the cellular modules by means of a suitable inverting transistor as shown in Figure 52,
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 device, so that it will switch on when V_INT output is
enabled.
According to the V_INT supply output voltage ripple characteristic specified in the TOBY-L3 series Data
Sheet [1], additional filtering may be needed to properly supply an external LNA, depending on the
characteristics of the used LNA, adding a series ferrite bead and a bypass capacitor (e.g. the Murata
BLM15HD182SN1 ferrite bead and the Murata GRM1555C1H220J 22 pF capacitor) at the input of the
external LNA supply line.
u-blox GNSS
1.8 V device
TxD1
SDA2
SCL2
VCC
1V8
C1
R3
5
V_INT
R5
R4
TP
T2
T1
R1 R2
1V8 1V8
GNSS data ready
GNSS supply enabled
22
GPIO2
SDA
SCL
GPIO3
55
54
24
TOBY-L3 series
Figure 52: Application circuit for connecting TOBY-L3 series modules to u-blox 1.8 V GNSS devices using V_INT as supply
Reference
Description
Part Number - Manufacturer
R1, R2
4.7 k Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
R3
47 k Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
R4
10 k Resistor 0402 5% 0.1 W
RC0402JR-0710KL - Yageo Phycomp