LISA-U2 series - System Integration Manual
UBX-13001118 - R19
Early Production Information
System description
Page 87 of 175
or a warm start (depending on the duration of the GNSS
VCC
outage) and to maintain the configuration
settings saved in the backup RAM.
“GNSS data ready” and “GNSS RTC sharing” functions are not supported by all u-blox GNSS receivers
HW or ROM/FW versions. See the
GNSS Implementation Application Note
[16] or to the
Hardware
Integration Manual
of the u-blox GNSS receivers for the supported features.
LISA-U2 series
R1
IN
OUT
GND
GPS LDO
Regulator
SHDN
u-blox GNSS
1.8 V receiver
SDA2
SCL2
R2
1V8
1V8
VMAIN
1V8
U1
21
GPIO2
SDA
SCL
C1
TxD1
EXTINT0
GPIO3
GPIO4
46
45
23
24
VCC
R3
V_BCKP
V_BCKP
2
R4
Figure 47: DDC Application circuit for u-blox 1.8 V GNSS receiver
Reference
Description
Part Number - Manufacturer
R1, R2, R4
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
U1
Voltage Regulator for GNSS receiver
See GNSS receiver Hardware Integration Manual
Table 38: Components for DDC application circuit for u-blox 1.8 V GNSS receiver
As an alternative to using an external voltage regulator, the
V_INT
supply output of LISA-U2 cellular modules
can be used to supply a u-blox 1.8 V GNSS receiver of the u-blox 6 generation (or later u-blox generation). The
V_INT
supply is able to withstand the maximum current consumption of these positioning receivers.
The
V_INT
supply output provides low voltage ripple (up to 15 mVpp) when the module is in active-mode or in
connected-mode, but it provides higher voltage ripple (up to 70 mVpp) when the module is in the low power
idle-mode with power saving configuration enabled by AT+UPSV (see the
u-blox AT Commands Manual
According to the voltage ripple characteristic of the
V_INT
supply output:
The power saving configuration cannot be enabled to use
V_INT
output to properly supply any 1.8 V GNSS
receiver of the u-blox 6 generation and any 1.8 V GNSS receiver of the u-blox 7 generation or any newer
u-blox GNSS receiver generation with TCXO.
The power saving configuration can be enabled to use
V_INT
output to properly supply any 1.8 V GNSS
receiver of the u-blox 7 generation or any newer u-blox GNSS receiver generation without TCXO.
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.
See the
GNSS Implementation Application Note
[16] for additional guidelines using the
V_INT
supply output of
LISA-U2 cellular modules to supply a u-blox 1.8 V GNSS receiver.