TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R07
Advance Information
Design-in
Page 113 of 158
Figure 63 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 62. 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 63,
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.
According to the
V_INT
supply output voltage ripple characteristic specified in the
TOBY-L2 Data Sheet
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 receiver
TxD1
EXTINT0
V_BCKP
V_BCKP
3
SDA2
SCL2
VCC
1V8
C1
R3
5
V_INT
R5
R4
TP
T2
T1
R1
R2
1V8
1V8
GNSS data ready
GNSS RTC sharing
GNSS supply enabled
22
GPIO2
SDA
SCL
GPIO3
GPIO4
55
54
24
25
TOBY-L2 series
(except ‘00’, ‘01’, ‘50’ versions)
Figure 63: Application circuit for connecting TOBY-L2 modules to u-blox 1.8 V GNSS receivers 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
R5
100 k
Resistor 0402 5% 0.1 W
RC0402JR-07100KL - Yageo Phycomp
T1
P-Channel MOSFET Low On-Resistance
IRLML6401 - International Rectifier or NTZS3151P - ON Semi
T2
NPN BJT Transistor
BC847 - Infineon
C1
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C104KA01 - Murata
Table 38: Components for connecting TOBY-L2 modules to u-blox 1.8 V GNSS receivers using V_INT as supply
For additional guidelines regarding the design of applications with u-blox 1.8 V GNSS receivers see the
GNSS
Implementation Application Note
[13] and the
Hardware Integration Manual
of the u-blox GNSS receivers.